DEER MANAGEMENT AT THE CRANE MEMORIAL RESERVATION AND WILDLIFE REFUGE A case study in conflict resolution and decision-Making to Meet the objectives set by The Trustees of Reservations A Charitable Corporation 224 AdaMs Street Milton, MA 02186 By Dr. Aaron N. Moen Professor of Wildlife Ecology DepartMent of Natural Resources College of Agriculture and Life Sciences Cornell University and Certified Wildlife Biologist The Wildlife Society Copies of this report May be purchased froM the publisher CornerBrook Press Box 106 Lansing, NY 14882
Transcript
DEER MANAGEMENT AT THE CRANE MEMORIAL RESERVATION AND WILDLIFE REFUGE
A case study in conflict resolution and decision-Making to Meet the objectives set by
The Trustees of Reservations A Charitable Corporation
224 AdaMs Street Milton, MA 02186
By
Dr. Aaron N. Moen Professor of Wildlife Ecology
DepartMent of Natural Resources College of Agriculture and Life Sciences
Cornell University
and
Certified Wildlife Biologist The Wildlife Society
Copies of this report May be purchased froM the publisher
CornerBrook Press Box 106
Lansing, NY 14882
First printing, NoveMber 1984
Copyright€) 1984 by Aaron N. Moen
No part of this book May be reproduced by any Mechanical, photographic or electronic process, or in the forM of phonograph recording, nor May it be stored in a retrieval systeM, transMitted, or otherwise
copied for public or private use without written perMission of Aaron N. Moen
Library of Congress Catalog NUMber 84-072928
ISBN 0-913523-03-8
i i
CONTENTS
INTRODUCTION . . The probleM ....... . The Trustees of Reservations
Responsibilities Objectives
HISTORY Crane MeMorial Reservation Crane Wildlife Refuge Deer populations and ManageMent
THE AGREEMENT Study paraMeters Advisory groups
STUDY FORMAT InforMation collected
Description of area Forage estiMates Deer observations .
Previous research and cooperators Previous research Cooperators . .
COMputer processing
THE BIOLOGICAL FRAMEWORK Deer data
Parturition date Deer weights Reproductive characteristics
Range data ........... . Plant cOMMunity characteristics Forage characteristics ... .
Population data ......... . Yearling age class frequencies Sex ratios EstiMated nUMbers
Metabolic characteristics ..... Base-line MetabolisM Multiple of base-line Ecological MetabolisM
.Body cOMposition .. Fat content . . Energy reserves
MetabolisM
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1 1 2 2 2
3 4 4 4 7 7 8
11 11 11 16 16 17 17 17 17
19 19 19 19 19 19 20 20 21 21 21 "'l"'l L.L
"'l7 LJ
23 23 25 27 27 27 28 28 28 28 29 29 29
RANGE PARAMETERS . . . . . Habitat types ....
Woodland habitats Openland habitats
Forage production Forage production in relation to habitat type Vertical distribution of forage production
Forage characteristics .. Cell cOMposition Digestibility rhythMs Protein content . . . Turnover tiMe . . . . Current forage quality
POPULATION PARAMETERS Sex and age class frequency distributions
Age-class frequency distributions Sex ratios
Weighted Means . . . . . Body weights Ecological MetabolisM Forage required
CALCULATIONS OF CARRYING CAPACITY AND POPULATION SIMULATIONS Carrying capacity calculations.
Crane MeMorial Reservation Crane Wildlife Refuge
Population siMulations
MANAGEMENT OPTIONS Do nothing .. Feed the deer Reduce the population
Trapping .... Regulated hunting AniMal control specialist
ECOLOGICAL CONSIDERATIONS Natural areas
Size considerations Diversity .....
Population interactions Predator-prey interactions Open-closed systeMs
Population potentials Population growth .. Persistence over tiMe EnvironMental iMpacts
Photo-pages of environMental iMpacts
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33 33 33 33 33 33 35 35 36 38 39 40 41
43 43 43 43 44 44 45 45
47 47 47 48 48
53 53 53 54 54 55 55
57 57 57 57 58 58 58 60 60 60 61 63
LEGAL, SOCIAL, AND ECONOMIC CONSIDERATIONS Legal considerations ..
Cruelty to aniMals Hunting regulations DaMage perMits
Social considerations EnjoYMent of nature LYMe disease Recent social changes
EconoMic considerations DaMage to property Protection froM daMage Medical treatMent and recovery
MANAGEMENT RECOMMENDATIONS AniMal control specialist Population reduction .
Trapping .... Regulated hunting
Population control .. Controlling nUMbers Controlling behavior
Wildlife ManageMent on natural areas A long-range restoration and recovery prograM
SUMMARY
LITERATURE CITED
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71 71 71 71 71
72 72 72 73 75 75 75 76
77 78 78 78 79 80 80 81 81 83
85
87
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INTRODUCTION
White-tailed deer <Qdocoileus virginianus), a relatively large (up to 250 pounds, 110 kg) wild herbivore and rUMinant, is present throughout the United states and southern Canada, and often becoMes locally abundant. It is abundant in the northeastern states, including Massachusetts. White-tailed deer adapt readily to suburban and rural residential areas such as the town of Ipswich in the northeast corner of Massachusetts, where the Crane MeMorial Reservation is located, and the town of Essex, where Most of the Crane Wildlife Refuge is located. This report is a case study in conflict resolution and decision-Making to gUide The Trustees of Reservations, which is responsible for Managing the Crane MeMorial Reservation and Crane Wildlife Refuge, as they seek to regulate the deer populations on these areas in accordance with stated objectives, within the regulations pertaining to wildlife in the state of Massachusetts.
The ProblePl
Perceived differences in the nUMber of deer and their iMpacts on the Crane areas have resulted in conflicts between various interest groups. An unpublished report (AnonYMous 1983) prepared jointly by the Massachusetts Division of Fisheries and Wildlife, The Trustees of Reservations, Harvard University School of Public Health, and the University of Massachusetts DepartMent of Forestry and Wildlife ManageMent includes the stateMent:
"Evidence indicates that the deer population in the Crane MeMorial Reservation ... has expanded beyond the carrying capacity of the habitat, resulting in the beginning stages of habitat destruction. The deer have also becoMe hosts of the adult deer tick, the vector of LYMe disease, thus posing a potential probleM for people in the Ipswich-Essex coastal area. LYMe disease has affected at least 2,000 residents of the northeastern United States during the past 10 years and can be severely debilitating."
A plan to reduce the deer population with a regulated hunt in the fall of 1983 was actively opposed by the Friends of AniMals, a national privatelyfunded organization. The regulated hunt was called off, and The Trustees of Reservations searched for a qualified consultant to evaluate the habitat and the deer on the Crane areas. This report is prepared in fulfillMent of a consulting contract between The Trustees of Reservations and the author to evaluate deer-range relationships on the Crane MeMorial Reservation and Wildlife Refuge, and present several ManageMent options for consideration.
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The Trustees of Reservations
The Trustees of Reservations, a privately-adMinistered, charitable corporation independent of governMent, was incorporated in 1891 to seek out and preserve for public enjoYMent "beautiful and historical places and tracts of land within this COMMonwealth" (AnonYMous No.1). The Crane MeMorial Reservation and Crane Wildlife Refuge are two of More than 70 properties owned and adMinistered by The Trustees of Reservations.
The governing board of The Trustees of Reservations is its 14-MeMber Standing COMMittee, whose MeMbers are elected annually by MeMbers of the corporation--150 persons--traditionally called "Trustees." There are also local COMMittees for Many of the Reservations, including the Crane properties.
Responsibilities
·Preservation in perpetUity" is the purpose of The Trustees of Reservations. Preservation of a property has a higher priority than public enjoYMent of that property if the two are in conflict. "ManageMent policies are deterMined by a planning process which identifies and describes the qualities and features of each property, and then reCOMMends procedures to provide for its continuing protection" (AnonYMous No.2).
Objectives
The Trustees of Reservations is responsible for preserving and Maintaining natural and historic areas for public use. General objectives for Managing the Crane MeMorial Reservation and the Crane Wildlife Refuge are given below.
The Crane MeMorial Reservation. The Trustees of Reservations and the Castle Hill Foundation Manage the Crane MeMorial Reservation for the purpose of protecting and restoring the natural and Man-Made environMents of Crane Beach and Castle Hill (AnonYMous No.1).
The Crane Wildlife Refuge. The Trustees of Reservations is COMMitted "To Manage the Crane Wildlife Refuge with thoughtful care which will best serve the total environMent, while preserving the balances between forest, field and indigenous wildlife" (AnonYMous No.3).
Objectives Qf this study. The objectives of this study are:
Knowledge of deer-habitat relationships on the Reservati6n and Refuge.
Understanding of potential iMpacts of different ManageMent deciSions on deer and habitat conditions.
Ability to predict population changes as a result of different ManageMent practices.
Insight into the potential threat posed by LYMe disease in relation to deer populations of different sizes.
Appreciation of the ecological COMplexity of both natural and Man-Made features on the Crane areas.
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HISTORY
The Ipswich area was originally inhabited by the AgawaM Indians. They planted corn and harvested finfish and shellfish froM the areas surrounding Hog Island. English settlers began arriving in the early 1600's. The land which includes the Crane MeMorial Reservation and Wildlife Refuge was farMed over the next few centuries and sheep, cows, and pigs were raised. Hog Island was nearly entirely cleared by the 1800's and was farMed into the 1900'5 (Lappen 1984 and Rizotti 1984).
Figure 1. The Richard T. Crane, Jr. MeMorial Reservation and the Cornelius & Mine S. Crane Wildlife Refuge (Map froM AnonYMOUS 1978).
The Richard T. Crane, Jr. MeMorial Reservation (Figure 1), given to The Trustees of Reservations by Mrs. Florence Crane and MeMbers of the Crane faMily beginning in 1945, is located on Argilla Road 3.5 Miles east of Route 1A and the Ipswich South Green. Mrs. Crane bequeathed Castle Hill to The Trustees of Reservations in 1949. The Cornelius and Mine S. Crane Wildlife Refuge, consisting of five islands and the surrounding salt Marsh in the Essex River Estuary, was given to The Trustees of Reservations in 1974 by Mrs. Mine S. Crane.
Five SUMMer hOMes were built on Hog Island in the late 1880's, after a bridge was built between Dean and Hog Islands. The bridge was destroyed in a storM in 1898. As More people becaMe SUMMer residents on Hog Island, farMing intensity decreased. Purchases of this coastal land which has becoMe the Crane Reservation and Wildlife Refuge by Richard T. Crane, Jr. resulted in Major changes in these areas.
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Crane MeMorial Reservation
The Richard T. Crane, Jr. MeMorial Reservation consists of about 1400 acres of beach, salt Marsh, Castle Hill with the Great House, and accoMpanying grounds. The land on Castle Hill and Castle Neck was farMed in the 1800's until sand dune Migration covered agricultural soils. Richard T. Crane, Jr. bought all of Castle Hill frOM the estate of a farMer, John BurnhaM Brown, in 1910. Mr. Crane acquired Many other surrounding properties in succeeding years, including Castle Neck, Hog Island, Long Island, and Round Island. The 59-rOOM Great House was COMpleted in 1927, after the razing of an Italian villa previously built on that site. Houses, garages, and barns were also built for eMployees, equipMent, and aniMals. The Great House was occupied by the Cranes until 1949. Today the buildings and apprOXiMately 165 acres of landscaped grounds are used for cultural purposes by the Castle Hill Foundation. The Crane MeMorial Reservation, adMinistered by The Trustees of Reservations, is open to the public.
Crane Wildlife Refuge
Richard T. Crane, Jr. purchased Hog Island and the surrounding islands and salt Marsh in 1916. Mr. Crane reMoved all structures but the large barn and the Choate House, which he considered historically significant. When Mr. Crane's son Cornelius acquired the property in 1941 he reintroduced sheep on the island and built the white cottage for the shepherd. The sheep were later reMoved, and in 1974 the refuge was donated by Mine S. Crane to The Trustees of Reservations. The Shepherd's cottage is now the Visitor Center. SOMe of the 40-year old conifer plantation was thinned by girdling between 1979-1982 as part of a tiMber stand iMproveMent prograM (Lappen 1984).
The 700-acre Cornelius and Mine S. Crane Wildlife Refuge was given to The Trustees of Reservations in 1974. The refuge consists of part of Castle Neck and five islands. Hog Island is the largest, with 135 acres of upland, Most of which is covered by conifers planted in the 1930's. Round Island has 13 acres of upland which was also planted to conifers in the 1930's. Long Island, 33 acres is connected by causeway and salt Marsh to Hog Island, and deer can Move freely between the two. The salt Marsh between the three islands covers about 70 acres. Dean and Dilly Islands are too SMall to support deer, except for occasional visits.
Deer Populations and ManageMent
Deer had been extirpated in the IpSWich-Essex area by the end of the 18th century. Thoreau (1894) gives an account by a neighbor in an 1853 journal entry: "Minott says his Mother told hiM she had seen a deer COMe down a hill behind her house .... Cross the road and the Meadow in front. Thinks it May have been eighty years ago." Thus the sighting of a deer in the 1770'5 reMained noteworthy eighty years laterl
Laws governing the taking of gaMe aniMals becaMe COMMon throughout the United States around the beginning of the 20th century, and the enforceMent of hunting regulations has resulted in draMatic recovery of Many ~pecie5, including deer. They could not have been abundant on Hog Island in the 1930'5
as the high rate of survival of the conifer seedlings planted then indicates that the seedlings were not under the intense browsing pressure encountered on the island today. One factor in maintaining a low deer population is that Mr. Crane allowed his staff to hunt deer on the property. Hunting is not allowed at present; trespass law is enforced by rangers hired during the hunting season.
A five-year study was begun in 1979, supervised by the Massachusets Division of Fisheries and Wildlife to deterMine the MoveMent patterns of the deer to the mainland froM Hog Island. Deer were ear-tagged, they have been counted on the ground and from the air, and their activities have been Monitored. Apple Mash has been used to attract deer to two feeding stations on Hog Island to facilitate counting.
The 1982-83 and 1983-84 winter populations on Hog Island were 65-75 deer. SOMe of the deer move off the island to the towns of West Gloucester, Essex, and Ipswich in the spring; the island population drops to 30-35 during the SUMMer. The high winter concentration of deer on the Refuge has resulted in heavily-browsed woody vegetation.
Over 160 deer have been counted on the Crane MeMorial Reservation in each of the past two winters. Twenty-two dead deer were found in partial surveys of the Crane properties in the winter of 1981-82, 3 in the mild winter of 1982-83, and 18 in the winter of 1983-84. AlMOSt all of the dead deer were less than one year old; they were fawns born the previous spring.
One concern about the deer population in the Ipswich area is the occurrence of LYMe disease, a spirochete infection (Anderson et al. 1983) which causes arthritis-like SYMptOMS with occasional serious complications. The disease was first reported on the East Coast in the town of Old Lyme, Connecticut in 1975, and has since been spreading on the Atlantic Seacoast. The vector of Lyme disease is the deer tick, Ixodes damMini (SpielMan et al. 1984). Ticks were discovered in routine tagging operations by the refuge Manager in 1982 (Lappen 1984). Eight residents along Argilla Road, from IpSWich to the Crane properties, contracted LYMe Disease in 1983, and about the saMe nUMber in 1984. Further, five of 27 SUMMer eMployees on Crane Beach tested in 1984 had contacted LYMe Disease. Scientists frOM the Harvard School of Public Health described the Hog Island tick population as the MOSt abundant they have seen (Spielman et al. 1984).
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6
THE AGREEMENT
This report is the result of an AGREEMENT drawn up by The Trustees of Reservations and Dr. A.N. Moen to evaluate deer ManageMent options at the Crane MeMorial Reservation and Crane Wildlife Refuge. Three Main considerations were included in the AGREEMENT, including deer biology and population characteristics, land use characteristics, and the potential threat of LYMe disease to visitors and its relationship to deer and other MaMMals. An advisory group was also forMed to represent the various interest groups that have expressed interest in the deer ManageMent prograM options to be considered.
Three Main properties.
questions They are:
were
study ParaMeters
asked concerning
1. Is there an overpopulation of deer?
deer ManageMent
2. Are the deer affecting long-terM survival of the habitat? 3. Is there a significant threat froM LYMe disease?
The AGREEMENT also included the following considerations:
on these
If there is an overpopulation of deer, habitat deterioration and/or significant threat froM LYMe disease, then the study should:
A. DeterMine three optiMuM deer populations based upon (1) no habitat deterioration, (2) no significant threat froM LYMe disease, and (3) ability to restore ornaMental plantings at Castle Hill.
8. Assist The Trustees of Reservations in deterMining optiMUM deer populations taking all three into account.
C. Identify all ManageMent options which are available to achieve the recoMMended deer population, with each option assessed froM the standpoint of effectiveness, hUMane treatMent of the aniMal, costs, etc. ManageMent options should include:
1. Do nothing. 2. Public hunting. 3. Sharpshooter hunting. 4. Lethal injections by dart guns. S. Capture and release elsewhere. 6. Fencing. 7. Feeding. 8. Repellants to protect plantings. 9. Sterilization by horMone injections or surgery.
Note that these questions pertain to the biological aspects of deer and their habitat.
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Advisory Groups
Several groups had expressed interest in the deer population and ManageMent probleM at the Crane properties, and representatives were selected by The Trustees of Reservations to Meet with Dr. Moen and The Trustees before the study began and upon cOMpletion of the first report. The follOWing groups were represented:
Friends of AniMals, Inc., Harvard University, School of Public Health, HUMane SOCiety of the United States, Massachusetts Division of Fisheries and Wildlife, Massachusetts Society for the Prevention of Cruelty to AniMals, Tufts University Veterinary Medical Center, United States Fish and Wildlife Service, and University of Massachusetts, DepartMent of Forestry and Wildlife.
Notes taken during discussions at the two Meetings with Advisory Group representatives are given below.
* * * * *
MEETING OF ADVISORY GROUP REPRESENTATIVES FROM FRIENDS OF ANIMALS·, THE HUMANE SOCIETY OF THE UNITED STATES, AND MASSACHUSETTS SOCIETY FOR THE PREVENTION OF CRUELTY TO ANIMALS, 3/28/84, GREAT HOUSE.
Mr. WilliaM C.Clendaniel opened the Meeting with a brief description of the responsibilities of The Trustees of Reservations.
TTOR PURPOSE: Preserving and Maintaining natural and historic areas for public use. Preserving is Most iMportant and takes precendence over public use.
TTOR GOAL FOR THE CRANE PROPERTIES: Restore and preserve the Great House and grounds, including Crane Beach. Make the Crane properties available for public use. The Crane MeMorial
Reservation generates considerable inCOMe for TTOR. RECENT HISTORY OF THE DEER HERD:
A deer study has been in progress for four years. Twenty-two dead deer were found in the winter of 1981-82. Deer ticks were found in late 1982. General policy of TTOR has not allowed hunting on its lands. Poaching has occurred in years past. Eight residents along Argilla Road contracted LYMe Disease in 1983.
QUESTIONS ABOUT THE DEER AND THE HABITAT: What is the "age" of the browse line? Could the browse line be 20 or More years old? Why is the population higher now than before? Why did the probleM beCOMe prOMinent in 1981-82? What should the habitat look like? Should the habitat look "park-like?" What does TTOR want the habitat to look like? Who will deterMine what the habitat should look like?
QUESTIONS ABOUT LYME DISEASE: Is it a significant threat here? Will reductions in deer nUMbers result in an increase of SMall MaMMals? Will increase in SMall MaMMal nUMbers cOMpound LYMe Disease probleMS?
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QUESTIONS ABOUT THE STUDY: How will the balance between deer and their resources be evaluated? How will the inforMation be cOMpiled? How is the weight curve Mentioned in the proposal derived? How are sex ratios deterMined? Will the inforMation gathered by others be used in the the study? What is happening to population nUMbers now? What inforMation is available on the deer population? Is the population stabalizing now? What about the diversities of vegetation, preferences, and
digestibilities?
IN RESPONSE TO A REQUEST FOR GENERAL STATEMENTS: T.E. Eveland, biologist for Friends of AniMals, Inc., requested that
starvation be given fair consideration as a controlling factor, as valid as predation and other causes of Mortality in wild populations.
* * * * *
MEETING OF ADVISORY GROUP REPRESENTATIVES FROM MASSACHUSETTS DIVISION OF FISHERIES AND WILDLIFE AND U.S. FISH & WILDLIFE SERVICE, 3/29/84, GREAT HOUSE.
Mr. WilliaM C. Clendaniel opened the Meeting with a brief description of the responsibilities of TTOR (See notes of 3/28/84).
QUESTIONS WERE THEN ASKED ABOUT THE STUDY, GROUPED INTO THE CATEGORIES BELOW.
QUESTIONS ABOUT THE HABITAT: How will the nutrient value of the Marsh be evaluated? Will the tiMe needed for habitat recovery be estiMated? How is forage being defined? How is forage being collected? What nutrient values do dry leaves have? How will forage saMples be handled?
QUESTIONS ABOUT THE DEER: What will be used as a source of inforMation on weights? What Methods can be used to estiMate-fat content?
QUESTIONS ABOUT LYME DISEASE: How do we evaluate ihe significance of LYMe disease? How can deer densities be evaluated in relation to LYMe disease?
QUESTIONS ABOUT METHODS OF DEER CONTROL: What dangers arise froM the use of drugs? What safe drugs are there? What concerns should be expressed for public safety? Suppose a drugged deer is lost and later eaten by dogs or wildlife? Is succinyl-choline hUMane since it iMMobilizes only?
QUESTIONS ABOUT THE STUDY REPORTS: Will I Make specific recoMMendations to If you do not recoMMend sOMething, will If you do recoMMend sOMething, will the How will the alternatives be evaluated?
TTOR? the reasons be given? reasons be given also?
To what extent? How Much inforMation will be provided for each alternative? Will a brief description of liMits of the Model be given? What restrictions will the copyright place on use of the Material?
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STUDY FORMAT
This report is based on cOMputer-processing of inforMation about the deer and the habitats on the Crane MeMorial Reservation and Wildlife Refuge. It is priMarily an analysis of carrying capaCity, with deer requireMents being analyzed with equations that have been prograMMed into the COMputer by A.N. Moen, and habitat characteristics being analyzed by both field work and equations relating forage production to deer requireMents.
Infor~ation Collected
InforMation about the area, the habitats, forage quantities and qualities, and the deer has been collected frOM field work and previously-published reports.
Descriotion Qf area
There are several types of deer habitat on the Reservation and Refuge, including dune vegetation, Mature hardwood stands, softwood stands, Meadows and Maintained grounds. These habitats provide different aMounts of food and cover for deer. The aMount of land in each habitat type has been deterMined frOM aerial photographs, USGS topographical Maps, and field work.
Habitats, Cran~ MeMorial Reservation. The Crane MeMorial Reservation covers an area of about 1400 acres. More than one-third of the area is sand beach, slightly less than one-third is covered by dune vegetation, and about one-eighth is covered by the salt Marsh which surrounds Castle Hill and Castle Neck on the inland side. Other habitat types are present in SMaller aMounts. A general vegetation Map is shown in Figure 2. A description of each type is given below. The two-character SYMbols at the beginning of each description are used on the Maps.
SH Shrub. Very heavy undergrowth of brush and shrubs. Consists of honeysuckle and black cherry, other brush species are also present, e.g. , grapes, pOison ivy, virginia creeper, bittersweet, bayberry, and barberry. Surrounds swaMPY area on Cedar Point and curls around below Cedar Point access road with SW exposure. 11 acres in 4 units.
OF Dune Forest. Consists priMarily of pitch pine; white pine, oak, red Maple, birch and ash are also present. It is located on Castle Neck in several scattered units. It has a hilly topography shaped by dune erosion; aspect and slope are variable. 317 acres in Many large and SMall units.
DV Dune Vegetation. A low ground cover of wooly hudsonia, low poison ivy bushes, and AMerican beachgrass Make up part of this classi other parts are covered by pOison ivy shrubs, bayberry, and occasionally vines and SOMe larger shrubs and trees. Slope and aspect are variable. 92 acres in Many SMall units.
11
FL P,3rk j ng 1 Jt
Figure 2. General vegetation Map of the Crane MeMorial Reservation, including Castle Hill \t.oP) and C,astle r~eck (bottOM). ':;ee Figure 1 for orientation.
1 ,.,
ME
1.
Meadow. Herbaceous fields with SOMe shrubs but few trees. Meadows are described below.
Meadows or occasionallY-Mowed of the Cedar Point access road. shrubs. 12 acres in 3 units.
fields on the downhill side Woody plants include sMall
2. Low, wet Meadows, one on the north side of the access road on Cedar Point, another east of the entrance road to the Great House. 5 acres in 2 units.
GR Grounds. This includes the Mowed lawns and grass parking lots located north of the gate house and near the steep hill beach. 33 acres in 9 units.
ST SawtiMber. Trees in the sawtiMber stage have a DBH of greater than 9 inches, generally reached when the trees are 40-50 years old. There are several stands on the Mainland, Most dOMinated by hardwoods. These are described below.
1. PriMarily Mature red pine with occasional hardwoods. Lowest forest belt on the west slopes of Castle and Steep Hills. There is little herbaceous understory, and the woody understory is varied. Slope is locally variable. 14 acres in 2 units.
2. Contains a greater percentage of hardwoods and larger than NUMber 1. Understory characteristics are siMilar to NUMber 1. Located in band above nUMber 1 and surrounding Much of the Maintained grounds. 78 acres in 1 unit.
3. East of Castle Hill on east side of inlet. Young stand of oak, Maple, and cherry. Bayberry, honeysuckle, and barberry understory is thick. 26 acres in 1 unit.
4. Oak trees larger than in NUMber 3, understory dOMinated by bayberry and honeysuckle. Transition area northeast of NUMber 3 between 3 and dune vegetation. 11 acres in 1 unit.
5. Mixed Mature hardwoods, priMarily Maple, on Cedar Point. Ground was wet in August. Understory priMarily woody plants, not as thick as in NUMber 6. 4 acres in 1 unit.
6. Mixed Mature hardwoods as in NUMber 5, but on drier site. The canopy closure is less and understory is thicker. 11 acres in 1 unit.
7. Mature pine trees with no understory due to dense canopy. Northwest of Steep Hill, in level area. 2 acres in 2 units.
8. PriMarily a willow canopy, with very thick understory. Located on north slope of Steep hill. 13 acres in 1 unit.
PL Parking lots with no vegetation, south side of Great House and at beach. 11 acres in 3 units.
SM Salt Marsh. Surrounds the inland side of Castle Hill and Castle Neck. 185 acres.
SB Sandy Beach. Sandy beach with general NE exposure the whole length of Castle Neck, Steep Hill, and Point. 502 acres.
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along Cedar
Habitats, Crane Wildlife Ref~. The Refuge, for purposes of this study, includes Hog, Long, and Round Islands. Dean and Dilly Islands, while technically part of the Refuge, are too SMall to support deer and the part of the refuge on Castle Neck was included in the analysis for the Reservation. Calculated acreage for the Crane Wildlife Refuge, including salt Marsh, is 260 acres (105 ha). Upland habitats cover about 190 acres. A general vegetation Map is shown in Fig. 3, and descriptions of each habitat are given below.
SH Shrub. Very heavy undergrowth of shrubs. Honeysuckle is the dOMinant shrub on the island; bayberry and barberry are also present. Areas are described below.
1. Located on east facing slope north of road to gravesite. This area was relatively open, providing SOMe herbaceous forage. 2 acres in 1 unit.
2. Located at elevations just below NUMber 1 and downslope to the Choate House. East exposure with variable slope. 7 acres in 1 unit.
3. Shrubs on northeast slope of SMall hill on Long Island. Very steep slope. No herbaceous vegetation present. 6 acres in 1 unit.
ME Meadow. Herbaceous fields with SOMe shrubs but few trees. Meadows are described below.
1. South slope of Long Island hill and field directly opposite it on Hog Island, and the south slope located south east of the Choate house. Mowed once or twice a year. 41 acres in 3 units.
2. These are located on Long Island near the boat landing, and near the causeway which links Long and Hog Islands. Low-lying fields which are Much drier than the ME-3 fields. Bayberry is present in these areas. 22 acres in 2 units.
3. This unit surrounds the landscaped gravesite of Cornelius Crane. This area has More shrubs than the Meadow class in general, but not enough to put it in the shrub class. 3 acres in 1 unit.
HR Hedgerow. These hedgerows are priMarily woody plants, especially honeysuckle invading underneath old apple trees. There are several hedgerows in the Middle of and on the edges of the field to the southwest of the Choate House. 2 acres in 5 units.
ST SawtiMber classes contain trees with DBH greater than 9 inches, and the stands are generally 40 or More years old. The conifer plantations on the refuge planted in the 1930's are in this stage now. Stands are described below.
1. Mixed conifers which Make up the largest land class on Hog Island. Also includes the red pine plantation on Round Island. Varying exposure on Moderately sloping ground. 71 acres in 2 units.
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Pine plantation on Round Island and north 2. Scotch Long Island. The understory is overgrown
end of with
honeysuckle. 9 acres In 2 units. 3. This is priMarily the edge of NUMber 2 which occurs on Hog
Island. Because it is on the edge the understory is thicker than NUMber 2. Located on the north. west, and south sides of Hog Island. 15 acres in 1 unit.
4. Less densely forested areas located within NUMber 2 and visible on the aerial photos. 1 acre in 2 units.
5. Cedar area which has greater canopy closure than the next class, NUMber 10, so understory is less thIck. 2 acres in 1 unit.
6. East of NUMber 10 and borders Mowed Meadows on east side. Honeysuckle is thick. 7 acres in 1 unit.
SM Salt Marsh. Located between Hog, Long, and Round Islands. 59 acres.
Meadows
Figure 3~ General vegetation Map of the Crane Wildlife Refuge.
15
Forage estiMates
The aMount of forage present I~as estiMated with a procedure developed by A.N. Moen and C.W. Severinghaus (MS in preparation) Stand characteristics were entered into a Radio Shack PC-2 cOMputer prograMMed to COMplete calculations of forage production and plot the vertical distrib~tion of the forage at each site in the field. The iMMediate output allows the field worker to evaluate the results while still at the site. Representative areas of each of the habitat types identified on the vegetation Maps were exaMined to deterMine the aMount of forage present. The field results, given in pounds of forage per acre, were Multiplied by the acreage of each habitat type to deterMine the aMount of forage present in each habitat. The SUM of all habitat types is an estiMate of the total aMount of forage available.
Deer Observations
Six visits were Made to the Crane Reservation and Wildlife Refuge by A.N. Moen in 1984, including one day in January, three days in March, three days in May, three days in August, one day in SepteMber, and two days in October-. Two visits were Made by R.A. Moen, Field Assistant, including three days in May and 10 days in August. Deer were observed on each of these visits, providing opportunities to COMpare deer on these areas with the thousands of observations Made by Dr. Moen in other areas in the United States and Canada. General observations frOM each of the visits are recorded below.
January, 1984. Several deer were observed in the bright sunlight on the south exposure below the Great House. They exhibited More piloerection and appeared to be More lethargic than expected under the conditions of bright sunlight and 15-20 degree (F) teMperatures. The deer were thin, and the forage had been heavily browsed. SOMe pellets were observed to be low in woody fiber, indicating that the deer were feeding on last year's herbivorous plant Material and grass exposed on the lawn.
March, 1984. A visit was Made to Hog Island whet~e ovet~ 40 deer IJJere observed. I was struck by the SMall size of a Marked yearling that Mr. Prisby pointed out. The deer were obViously thin, their ribs were showing, and the belly appeared distended, giving theM a "pot-bellied" look cOMpared to deer on good forage. The shrubs were very heavily browsed, and it was difficult to find even a single unbrowsed twig on Many of theM, except where the geOMetry of the branch protected twigs with buds. "The deer COMe quickly to feed on branches that are pruned frOM apple trees" Mr. Prisby said. He also noted that rUMens of deer found dead were filled with Marsh hay and conifer needles.
~ 1984. The deer were still in IJJinter coat, though Molting had begun and patches of hair had fallen out. The SUMMer coat usually appears about Mid-June. The ribs were visible on one deer observed close-up at the edge of the road. An adult doe was carrying a fawn or fawns; parturition should occur early in June for Most of the feMales.
August, 1984. R.A. Moen ground-truthed inforMation taken frOM aet-ial photos, did COMputer evaluations of forage quanitities in different land classes, and COMpiled a record of deer and other aniMals sighted while working in the field in August, 1984. Several bucks were seen with antlers in velvet.
16
Only one set of twin fawns was observed. Deer were seen in Mature forest stands, dune vegetation, the salt Marsh, lawns, and shrub areas.
SepteMber, 1984. Eight deer were observed while collecting forage the Morning of SepteMber 17. One buck with sMall antlers was observed; the velvet had been shed. spots were fading and winter pelage appearing on fawns. Older aniMals had winter coats, but MaxiMUM hair depth had not been reached at this tiMe.
Previous Research and Cooperators
The white-tailed deer is probably the best-studied wildlife species. Over 6,000 scientific publications on whitetails are listed in the 7-Part series on The Biology and ManageMent of Wild RUMinants (Moen 1980-1982). These publications are found in over 1,000 different serials and books.
Previous Research
Previous research by biologists has contributed large aMounts of data on white-tailed deer which has been invaluable when COMpleting the data base currently in COMputers used in research by Dr. Moen at Cornell University. Support for the long-terM research prograM has been provided by the New York State DepartMent of EnvironMental Conservation and the College of Agriculture and Life Sciences at Cornell, and is gratefully acknowledged. The assistance of Ronald A. Moen (B.S., Cornell University), in field work, data proceSSing, and COMpletion of this report is also gratefully acknowledged.
Cooperators
The cooperation of biologists and research scientists with the Harvard School of Public Health, Massachusetts Division of Fish and Wildlife, and Tufts University Veterinary Medical Center is Much appreciated. Further, personnel frOM The Trustees of Reservations, especially WilliaM C. Clendaniel, Mike GorMley, Wayne Mitton, and Walter Prisby, have been Most helpful in providing whatever inforMation is available and needed.
COMputer Processing
The inforMation collected during field visits and frOM previous research has been used to set up a cOMputer-based inforMation processing systeM for analyses of deer condition, reproductive rates, nutritional status, and population dynaMics. The cOMputer-based processing systeM May be updated annually, providing the Most current analysis of aniMal-range relationships possible. Such an approach Makes it possible to evaluate the effectiveness of decisions Made in relation to Dbjectives set.
The biological fraMework discussed next includes brief descriptions of deer and range data needed to deterMine an appropriate population for the resources available on the Crane properties. This is followed by discussions of the deer and range data used, and of population evaluations which contribute to the understanding necessary to Make ecologically sound decisions when Managing the deer popUlation and other natural resources on the Crane Properties.
17
18
THE BIOLOGICAL FRAMEWORK
AniMal and environMent forM an inseparable pair, and it is iMperative that both aniMal requireMents and range resources be evaluated together if carrying capacity is to be evaluated properly (Moen 1973). Using algorithMs that have been derived froM research on white-tailed deer by Many researchers over the years, liMited aMounts of data May be used to generate overall representations of aniMal-range relationships. For exaMple, energy MetabolisM rhythMs over the annual cycle May be calculated as a function of tiMe of year and reproductive status (Moen 1978). The calculation of energy requireMents is related to energy available on the range when evaluating carrying capacity. Deer data, range data, and population data are SUMMarized below.
Deer Data
Three iteMS of deer data are needed when calculating their energy requireMents over the annual cycle, including the Mean parturition date, weights over the annual cycle, and reproductive characteristics of different age classes. These data are used to calculate Metabolic rates, body COMpOSition, and forage requireMents.
Parturition date
The 31
Mean parturition date for (JDAY 151). This date is
deer in the Crane area May be estiMated as May used when deterMining the age in days (AGDA) of
For exaMple, a fawn-of-the-year is 167 days deterMined by subtracting 152 frOM 319, and
deer in different age classes. old on NoveMber 15 (JDAY 319), older deer are 365 days older in each successive age class.
Deer weights
The annual weight cycle of deer in different age classes has been deterMined using the procedures described in Moen and Severinghaus (1981). The few deer weights available for the Crane areas indicated that the lowest weight curve for deer in New York State, frOM the Adirondack Mountains, could be used as a realistic first approxiMation.
Reproductive characteristics
Reproductive rates are related to body weights at breeding; larger feMales have a higher conception r~te. Further, the average antler beaM diaMeter of the Male yearling age class is a good predictor of the reproductive rates of fawns, yearlings, and adults (Severinghaus and Moen 1983).
Range Data
Deer condition is directly related to the overall condition of the range. Forage relationships are particularly iMportant because productivity is directly related to the availability of nutrients. Thus plant COMMunity and forage characteristics are used to describe the range and estiMate the forage energy available to the deer population throughout the year.
19
Plant COMMunity Characteristics
Plant cOMMunity characteristics affect forage producion by affecting growing conditions in the understory. The stage in succession is particularly iMportant. High forage production occurs in the early stages in succession when plants are invading and an overhead canopy has not yet developed, and low forage production occurs when the canopy is well-developed and dense, allOWing little light to penetrate to the understory.
The age of a tiMber stand May be used to estiMate the aMount of forage available. Herbaceous plants and shrubs provide a large part of the forage available during the regeneration stage. Tree seedlings are beCOMing established, and forage production is at MaxiMUM at heights to which deer can reach 5-20 years after regeneration begins. In the sapling stage trees have a diaMeter at breast height (OBH) of 1 to 4 inches. The light at ground level is diMinished due to the developing canopy, 50 ground-level forage production is decreased. Increasing plant tissue production is occurring above the height which deer can reach. Most plant tissue production occurs in the canopy above the deer when trees are in the poletiMber stage, with a OBH of 4 to 9 inches, and the sawtiMber stage, with Mature trees having a OBH }9 inches.
Forage characteristics
Two Main evaluating production
forage characteristics--quantity and quality-- are considered when the nUMber of deer that can be supported on the range. Forage
and forage COMposition and digestibility are discussed below.
Forage Production. Forage production May be estiMated directly with on-site evaluations using rapid non-destructive visual procedures described in the Manuscript in preparation by C.W. Severinghaus and A.N. Moen, or indirectly by relating forage production to plant COMMunity and tiMber stand characteristics. Equations and COMputer algorithMs will be described in the preViouslY-Mentioned MS in preparation. The aMount of forage produced per unit area was estiMated for The Crane MeMorial Reservation and Wildlife Refuge in relation to stand characteristics using the cOMputer-based systeM for evaluating stand characteristics and cOMpleteing forage production calculations on site. The general pattern of forage production in relation to tiMber age classes is illustrated in Figure 4.
Forage COMposition. Forage saMples were collected on the Crane properties in March, May, August, SepteMber, and October, and analyzed for cell COMpOSition, crude protein, and Mineral contents. Cell COMposition data are used to estiMate digestibilities and crude protein fractions May be interpreted in relation to MiniMUMS necessary to Maintain a nitrogen balance.
Forage digestibilities. Forage digestibilities through the year are iMportant considerations when deterMining the aMount of forage required to support a population. The nUMber of species conSUMed and variability in plant parts taken throughout the year Makes accurate MeasureMents of species digestibilities difficult and tiMe-conSUMing. Analyses of deer diets and cell COMposition provide enough inforMation to derive a general pattern of diet digestibility throughout the year, however.
Figure 4. The general pattern of forage production in relation to age of the tiMber stand. MaxiMuM production May reach several hundred pounds.
Population Data
Four key population data are needed for the algorithMs used to predict populations. They are: yearling age class frequencies, sex ratio of faw~s,
sex ratio of yearlings and adults, and estiMated nUMber of deer. All of these algorithMs are described in Manuscripts in preparation by A.N. Moen and C.W. Severinghaus.
Yearlina aoe-class frequencies
Yearling age class frequencies of both Males and feMales are used to estiMate age-class population structure, including all age classes through 5+ years. The age-class frequency of yearling Males is estiMated froM a general knowledge of herd history, and the age class frequency of yearling feMales is calculated froM the reproductive rates of feMales. Frequencies of age classes two years and older are calculated with an exponential algorithM.
~ ratios
Sex Ratio g£ Fawns. The sex ratio of fawns at birth is an iMportant paraMeter when predicting population dynaMics as it is a partial deterMinant of the nUMber of reproducing feMales in a population. It is predicted froM yearling antler beaM diaMeter, an indicator of deer productivity.
Sex Ratios g£ Yearlings and Adults. The sex ratio of the yearling and adult portion of the population is an essential paraMeter for predicting population dynaMics. It is iMpossible to Measure directly, however. The ratio depends on the history of the population. Deer populations which are hunted have relatively fewer Males than those which are not hunted.
21
EstiMated nUMbers
The estiMated nUMber of deer in a population is used at the start of a cOMputer-based analyses, followed by cOMparisons of new estiMates and trends with the nUMbers predicted by population analyses. If nUMbers have not been estiMated in the field, then cohorts of any size May be evaluated for proportional changes in nUMbers.
22
DEER PARAMETERS
The deer paraMeters discussed below are used in the calculations of carrying capaCity as energy requireMents are deterMined and related to the energy resources on the range.
Annual Weight RhythMS
Annual weight rhythMs provide inforMation on increases and decreases in body weights through the year as deer aCCUMulate fat during the SUMMer when forage resources are More abundant, and Mobilize fat during the winter when forage resources becoMe less abundant. This is part of an overall energy conservation strategy (Moen 1976) characteristic of deer in northern states.
Male weicht rhythMS
Annual weight rhythMs of Male deer are calculated with a sine wave algorithM that fluctuates between MaxiMUM and MiniMUM weights through the year (Moen and Severinghaus 1981).
MaxiMuM live weights. Ma:dMuM live weights of SMall deer such as tho5e in the Adirondacks of New York State and the Crane properties, May be calculated with the follOWing equation:
where 3.13 0.45958
AGDA
MXMK = 3.13*AGDA~0.45958,
AXFK = a-value for MaxiMUM Male weight in kg, BXFK = b-value for MaxiMUM Male weight in kg, and age in days on the JDAY of MaxiMUM weight.
Calculated MaxiMUM Male weights in kg and pounds on October 28 (JDAY 301) are given in Table 1.
Table 1. Calculated Ma>dMUM weights of Males in age classes 0 to 5., in kg ( MXMK ) and pounds (MXMP).
Annual weight cycles. The annual weight cycle of Males is calculated with an aSYMetric sine wave equation (Moen and Severinghaus 1981) which includes the MaxiMUM and MiniMUM weight equations given above and the priMary and secondary phase corrections. Phase corrections were deterMined within the COMputer prograM frOM the inputs for JDAY of MaxiMUM Male weight (JXMW = 301) and JDAY of MiniMUM Male weight (JNMW = 106). Calculated Male weights are plotted in Figure 5 below.
READ Y-AXIS IN POUNDS 240-+ +-240
-120
+-100
80-+ +-80
60-+ +-60 YCl0
40-+ +-40
20-+ +-20
0-+-+----+----+----+----+----+----+----+----+----+----+----+-+-0 JAN FEB MAR APR MAY JUN JUl AUG SEP OCT NOV DEC
Figure 5. Annual rhythMs in Male deer weights.
24
FeMale weight rhythMs
Annual weight rhythMs of feMale deer are calculated with a sine wave algorithM that fluctuates between MaxiMUM and MiniMUM weights through the year (Moen and Severinghaus 1981).
Ma;dMUM live weights. The relationship between AGDA and MaxiMUM feMale weight in kg May be represented with the following regression equation in which AGDA is the independent variable and MXFK (MaxiMuM feMale weight in kg) is the dependent variable. The equation is:
where 10.9725 -23.4
AGDA
MXFK=10.9725*lN(AGDA)-23.4;
AXFK a-value for MaxiMUM feMale weight in kg, BXFK b-value for MaxiMUM feMale weight in kg, and age in days on the JDAY of MaxiMUM weight.
MaxiMUM weight of feMales is reached on October 28 (JOAY 301). Calculated MaxiMUM feMale weights in kg and pounds are given in Table 3.
Table 3. Calculated MaxiMUM weights of feMales in age classes 0-5, in kg (MXFK) and pounds (MXFP).
MiniMUM live weights. MiniMUM weights through the annual cycle are estIMated to be about 85% of MaxiMUM weights, reached on MAY 1(JDAY 121). MiniMUM feMale weights in kg (MNWK) are calculated with the equation:
where -28.85 9.23499
AGDA
MNFK=9.23499*106(AGDA)-28.85,
ANFK = a-value for MiniMUM feMale weight in kg, BNFK = b-value for MiniMUM feMale weight in kg, and age in days on the JDAY of MiniMUM weight.
MiniMUM weights of feMales are given in Table 4.
25
Table 4. Calculated MlnlMUM weights of feMales in age classes 0-5, in kg (MNFP) and pounds (MNFKl.
Annual weight cycles. The annual weight cycle of feMales is calculated with an aSYMetric sine wave equation (Moen and Severinghaus 1981) which includes the MaxiMUM and MiniMUM weight equations given above and the priMary and secondary phase corrections. Phase corrections are deterMined within the COMputer prograM frOM the inputs for JDAY of MaxiMUM feMale weight (JXFW 301) and JDAY of MiniMUM feMale weight (JNFW = 121). FeMale weights through the annual cycle are plotted in Figure 6.
READ Y-AXIS IN POUNDS 200-+ +-200
180-+ +-180
160-+ +-160
140-+ YCl5 +-140 I
~~::: YCLl
}-80 I
+-60 YCl0
+-40
+-20
0-+-+----+----+----+----+----+----+----+----+----+----+----+-+-0 JAN FEB MAR APR MAY JUN JUl AUG SEP OCT NOV DEC
Figure 6. Annual rhythMs in feMale deer weights.
26
Reproductive Characteristics
Reproductive rates and sex ratios are fundaMental reproductive paraMeters that Must be known or estiMated when Making population predictions. Values used for the Crane Reservation and Wildlife Refuge are discussed below.
Yearling antler beaM diaMeters
Yearling antler beaM diaMeters are good predictors of reproductive rates of feMale white-tailed deer (Severinghaus and Moen 1983). This correlation exists because Males and feMales coexist on the saMe range, and antler growth, Measured by the beaM diaMeter about two CM above the base, reflects range conditions which also affect the productivity of the feMales. Larger antler beaM diaMeters and higher body weights are characteristic of deer on good range, and sMaller antler beaM diaMeters and lower body weights are characteristic of deer on poor range.
EstiMated reproductive ~
The reproductive rates of feMales bred as fawns (FARR), yearlings (YERR), and adults (ADRR) May be predicted with the following equations (Severinghaus and Moen 1983), where YABD is the independent variable:
FARR=0.078 wYABD-l.135, YERR=0.151*YABD-1.344, and ADRR=0.072*YABD+0.463.
The YABD of deer with low weights, such as those on the Crane properties, is expected to be between 12 and 15 MM; Calculated reproductive rates based on these YABD are given in Table 5.
Table 5. Calculated reproductive rates of fawns, yearling, and adult does in relation to average Male yearling antler beaM diaMeter in MM.
YABD 12MM 15MM
FARR 0.00 0.04 YERR 0.47 0.92 ADRR 1.33 1.54
27
Metabolic Characteristics
Metabolic characteristics May be calculated through the annual cycle and the energy cost of living and forage required to Meet this cost estiMated. Three paraMeters, base-line MetabolisM per day, Multiple of base-line MetabolisM, and ecological MetabolisM per day, are used to estiMate the Metabolic rate, using the equations discussed in Moen (1978 and 1981a).
Base-line MetabolisM per day
Base-line MetabolisM per day (BlMO) is calculated with the following forMula:
where 70 IFWf<
a MatheMatical constant, and ingesta-free weight in kg.
Ingesta-free COMposition, et a1. (1974):
weight in kg (IFWK), used when calculating MetabolisM and body is estiMated with the follOWing forMula, siMplified frOM Robbins
IFWK=0.9*ClWK.
Multiple of base-line MetabolisM
The Multiple of base-line MetabolisM through the annual cycle May be calculated with a detailed sine wave forMula in Moen (1978), in which MBlM f(tiMe of year and nUMber of fawns). A late fall to early spring average MBlM of 1.8 May be used for both Males and feMales, since they are siMilar during that tiMe. In late spring feMales experience riSing energy costs of gestation, especially in the last third of gestation, followed by an additional cost for lactation.
Ecological MetabolisM
Ecological MetabolisM short forM:
MetabolisM per day is deterMined by Multiplying by the Multiple of base-line MetabolisM for the given
ElMD=BlMO*MBL.M.
base-line JOAY. In
The equations for BL.MO and MBLM are COMbined into a final overall equation for EL.MO in the COMputer prograM which is used to calculate the energy cost of living.
28
Body COll1position
The weight changes through the year reflect changing fractions of fat and water. Protein and ash contents reMain fairly constant at about 20% and 3%, respectively. As weights increase, the fat fraction increases and the water fraction decreases (Robbins et al. 1974a). These changes through the year represent changes in energy reserves available during tiMes of MetabolIC stress, such as late winter.
Fat content
The equation used to calculate the fat content in kg (FATK) of white-tailed deer as a function of ingesta-free weight in kg is (Modified frOM Moen 1980):
Th~ fat contents and fat fractions of both Males and feMales at peak weights are given in Table 6. The percent of ingesta-free weight represented by fat is illustrated in Figure 7.
Energy reserves
The fat content of the body represents an energy reserve which is Mobilized when daily intake is not sufficient to Meet the daily energy cost of living. The fat contents given above May be used to estiMate the potential fat contribution to the Metabolic requireMents when the deer go frOM MaxiMUM to MiniMUM weight. The caloric contribution of the fat to the Metabolic requireMents and the fraction of the Metabolic requireMents represented by the fat are given in Table 7. The contribution of the fat reserve to the average daily Metabolic requireMent is illustrated in Figure 8.
Table 6. Fat contents and fat fractions of Male and feMale deer at peak weights.
Figure 7. Fat content of deer at peak weights, expressed as percent of ingesta-free weight, in relation to age in years. (Oata froM Table 6).
Table 7. MaxiMUM and MiniMUM weights of deer, fat contents, and fat characteristics in relation to average daily Metabolic rate frOM late fall to early spring.
DEFINITIONS OF TABLE HEADINGS: AGCl Age class MXIK MaxiMUM ingesta--free weight FTKX Fat content in kg at MaxiMUM weight MNU: MiniMUM ingesta-free weight FTKN Fat content in kg at MlnlMUM weight
MDPT IFWK Midpoint ingesta-free weight in kg ELMD Ecological MetaboliSM per day
KG KilograMs KCAl ~:ilocalories contribution of fat Mobilized to ELMO PCNT Percent contribution of fat Mobilized to ELMO
30
READ Y-AXIS AS PERCENT
30 + Male
25 + ---- FeMale
20 +
15 +
10 + I 5 + I
o ~---I+!---+--- +----+---0.5 1.5
I I
I I I +1 ___ + __ - + ____ + __ _
2.5 3.5 AGE IN YEARS
I I I
I I I
+ 30
+ 25
+ 20
+ 15
+ 10
+ 5
+----+--- +----+ 4.5 5.5
Figure 8. Contribution of the fat reserves to the average daily Metabolic requireMent of deer of different ages in the winter. (Data froM Table?),
Note that the fat reserve contributes about 4 to 10% of the energy required daily by Male and feMale deer 0.5 and 1.5 years old, and by feMale deer to 5.5 years old. The younger deer are More dependent on forage since their fat reserves are sMaller than those of older deer. Yet older deer have the advantage when foraging; physically they are larger and behaviorally they are dOMinant.
31
32
RANGE PARAMETERS
Range paraMeters used to estiMate the resources available to the deer include woodland and openland habitat characteristics, forage production relation to habitat characteristics, and digestibilities of herbaceous woody plant Material through the annual cycle.
Habitat Types
herd in
and
Habitat characteristics, including local forest type, age of the stand, and canopy density May be used to Make estiMates of forage production with procedures described in Manuscripts in preparation by A.N. Moen and C.W. Severinghaus. Field work is then COMpleted in order to COMpare the predictions based on habitat characteristics with on-site production estiMates. Habitats on the Crane properties May be divided into two COMpartMents: the Crane MeMorial Reservation and the Crane Wildlife Refuge. The woodland and openland habitats in these units have been evaluated separately for estiMates of forage production. Results of these MeasureMents are discussed below.
Woodland habitats
Woodland on the Crane Reservation and Refuge consits of a shrub stage, dune forest, and sawtiMber age class. The sawtiMber class May be further divided into hardwood stands, which occur on the Reservation, and coniferous stands, which occur on the Refuge.
Qpenland habitats
Openland on the Crane Reservation and Refuge consists of Meadows, grounds, salt Marsh, parking lots, sand dunes, and beaches. Meadows are open fields which May be occaSionally Mowed. Grounds are Maintained with lawn Mowers cutting to a height of about two inches. The salt Marsh produces herbaceous forage; 60 of the 244 acres of salt Marsh were conSidered accessible to deer. Parking lots and sand beaches do not provide forage for deer.
Forage Production
Forage supplies the nutrients, including energy, which Meet the requireMents for Maintenance and productivity. Forage production has deterMined in the follOWing ways.
Forage production in relation to habitat ~
daily been
Visual estiMates of stand characteristics were Made in 62 stands using the UNIVERSAL KEY (Moen and Severinghaus In Press) and a portable COMputer which COMpleted calculations of forage available and plotted the vertIcal distribution of forage production at each site. The results for the Crane MeMorial Reservation are SUMMarized in Table 8 and for the Crane Wildlife Refuge in Table 9.
33
Table 8.
Habitats
WOODLAND
Shrub stage Dune forest SawtiMber,
Average field-estiMated dry-weight forage production allocated to deer in different habitats on the Reservation.
Production, gounds/acre Acres Total groduction Herbs Woody SUM H+W Herbs Woody SUM H+W
* 60 acres total in salt Marsh; 15 acres considered accessible to deer.
34
Vertical distribution gf forage production
The vertical distribution of plant growth depends on the life-forMs of the species, unless SOMe additional factor(s) affect the plants in the understory. Deer have Markedly affected the vertical distribution of forage in the shrub and forest stands on the Crane areas. Less than 10% is found in the lowest 20-inch layer, less than 15% in the second layer, about 33% in the third layer, and alMost 50% in the fourth 20-inch layer, which is out of reach of Many of the deer, as illustrated in Figure 9. These six field-generated plots were drawn by the COMputer at each site.
o POUNDS/ACRE 200 o POUNDS/ACRE 200 o POUNDS/ACRE 200
Figure 9. Vertical distribution of forage production by woody plants in four 20-inch layers at six sites on the Crane areas. Note that the greatest aMount is in the top 20-inch layer (60-80 inches), out of reach of Many of the deer.
Forage Characteristics
Forage characteristics May be described by cell structures of different forages, digestibility rhythMs through the annual cycle, protein contents, and the current forage quality as indicated by a "first bite-next bite" analysis. These are discussed next.
35
~ cOMposition
Percent acid detergent fiber, predicted digestibility coefficient, and crude protein contents of 34 forage saMples collected on the Crane areas in 1984 are given in Tables 110 and 11 which follow. The following cell cOMponents and abbreviations are used in the tables:
PADF = Percent acid detergent fiber. The fraction of fiber in the forage containing low-digestibility Matter such as lignin and cellulose.
porc Predicted digestibility coefficient. These data have been deterMined froM in vitro digestion trials. In vivo digestibility May be less due to the presence of cheMical cOMpounds which inhibit digestion in Mixed diets.
crude protein. The total protein equivalent including nitrogen frOM both protein and non-protein sources. About 1% More than available protein, protein 1974b ).
crude protein contents of less than 5% do not return sufficient to the aniMal to be worth ingesting (Moen 1973 and Robbins et al.
Table 10. Percent acid detergent fiber (PAOF), predicted digestible energy coefficient (POIC), and crude protein contents of forages froM woody plants on the Crane MeMorial Reservation and Crane Wildlife Refuge.
'" '" '" COLLECTION DATE MARCH 28, 1984, (JOAY 87 ) '" * *
FORAGE PLANT PART PHENOLOGY PAOF POlC CPRT
Apple pulp 310.10 710 5.2
Bayberry unbrowsed twigs 2-5 CM dorMant 49.7 16 7.5
Bayberry browsed twigs 2-5 CM long dorMant 52.10 13 5.8
Blueberry, unbrowsed twigs to highbush 25 CM long dorMant 38.6 34 8.9
Blueberry, browsed twigs to highbush 15 CM long dorMant 63.5 17 8.1
Cedar, unbrowsed leafy Eastern Red tips green 37.5 42 7.5
Cedar, browsed tips Eastern Red 2-5 CM long dorMant 51.1 310 4.2
Table 11. Percent acid detergent fiber (PAOF), predicted digestible energy coefficient (POlC) and crude protein contents of herbaceous forages collected on the Crane MeMorial Reservation and Crane Wildlife Refuge.
FORAGE PLANT PART PHENOLOGY PAOF POlC CPRT
* * * COLLECTION DATE MARCH 28, 1984 (JOAY 87) * * *
"* "* * COLLECTION DATE JUNE .., 1984 (JOAY 152 ) * "* * i..,
M L><ed herbs tips of leaves early new growth 32.1 56 24.5
Beachgrass tips of leaves early growth 47.8 57 18.3
Carex sp. tips of leaves early growth 34.1 46 18.8
Digestibility rhythMs
Digestibilities have been Measured with in vitro digestion techniques and in vivo digestibilities calculated. Predicted digestibility coefficients (POlC) range froM as low as 13% to as high as 70%. Since forage digestibility is priMarily a function of plant cell structure, the digestible energy coefficients of different plants follow their phenology through the growing season. Analyses of the forages given above along with published data (See Moen 1981b) provide the inforMation necessary to derive the annual digestibility rhythM shown in Figure 10.
38
READ Y-AXIS AS FRACTION DIGESTIBLE 1.0 + + 1. 0
0.9 + + 0.9
0.8 + + 0.8
0.7 + + 0.7
0.6 + + 0.6
0.5 + + 0.5
0.4 + + 0.4
.,~ . 0.3 + . ::-.. + 0.3 .. 0.2 + + 0.2
0.1 + + 0.1
0.0 +--+----+----+----+----+----+----+----+----+----+----+----+--+ 0.0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Figure 10. General pattern of forag~ digestibility superiMposed on the data points for forages collected on the Crane areas.
Protein content
Protein content varies seasonally and by plant type and part. values below 5% are too low for the Maintenance of a nitrogen 1973). Woody browse collected on the Reservation and Refuge crude protein and herbaceous plant Material 15-35% crude protein values are given in Tables 10 and 11 (pages 36-38), rhythM of crude protein contents is illustrated in Figure 11.
READ Y-AXIS AS PERCENT CRUDE PROTEIN 0.25 +
0.20 +
0.15
0.10 +
0.05 + ,...------_....-
Crude protein balance (Moen
contained 4-9% protei n. Crude
and an annual
+ 0.25
+ 0.20
0.15
+ 0.10
+ 0.05
0.00 +--+----+----+----+----+----+----+----+----+----+----+----+--+ 0.00 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Figure 11. General pattern of crude protein superiMposed on the data pOints for forages collected on the Crane areas.
39
Turnover ~
Forage quality is not only a function of its digestibilty, but also the tiMe needed for the forage to be processed by the rUMen Microflora. There is an upper liMit to the physical capacity of the rUMen and reticulUM, 50 forage Must have a reasonable turnover tiMe since the deer eats each day, adding to the ingesta being Metabolized by the rUMen Microflora.
Knowing the ingesta weight (Robbins et al. 1974a) Makes it possible to calculate the turnover tiMe needed for forages with different digestiblities in order to prevent the aCCUMulation of undigested forage in the rUMen and reticulUM. The general forM of the relationship is:
where IWDK 4500 0.82 DECO IWWK ELMO
Turnover rate = (IWDK*4500*.82*DECO)/(IWWK*ELMO)
Ingesta weight dry in kg, Kcal/kg forage, Metabolizable energy coefficient, Digestible energy coefficient, Ingesta weight wet in kg, and Ecological MetaboliSM per day.
Results of analyses of different COMbinations of DECO frOM 0.20 to 0.80 and CLWK frOM 20 to 100 kg are given in Table 12.
The data in Table 12 indicate that SMaller deer should conSUMe More didgestible forage with a More rapid turnover tiMe than larger deer in order to prevent the aCCUMulation of ingesta in the rUMen. The basic reason for this is the relatively SMaller rUMen capacity of SMall deer cOMpared to large deer (Moen 1973). However, forage conSUMed by SMall deer is not More digestible than that conSUMed by large deer; it is More likely to be less digestible on heaVily-browsed range because SMaller deer cannot reach as high as larger deer 50 they MUSt eat what is left over at the lower heights. The effect of this relationship is that SMall deer, when they are found dead frOM starvation, have rUMens filled with undigested Material which aCCUMulated in the latter stages of starvation as the Microflora were unable to break down the low-quality forage conSUMed on depleted range.
40
Table 12. Calculated turnover tiMes necessary for continued processing of forage with digestible energy coefficients (DECO) frOM 0.20.to 0.80 by deer weighing froM 20 to 100 kg. DECO values to the left of the line are too low for continued digestive efficiency, and ultiMately, survival.
*The equation for ingesta-free weight is given on page 28, frOM which ingesta weight wet (IWWK) May be calculated.
Current forage quality
What is the quality of the forage currently available to the deer on the Crane Properties? Two evaluations provide inforMation on the cell charactreristics and predicted digestibilities. One, the "first bite-next bite" cOMparisons show a distinct drop in digestibilities (Figure 12, frOM data in Tables 10 and 11). Two, the rUMen contents of a deer which died in early April, 1984 had a predicted digestibility coefficient of only 17%. This is way below the diet digestibility sufficient to support a SMall deer; the deer died with its rUMen filled with very low quality plant Material. The accuMulation of such low quality forage results frOM the daMMing-up effect as hungry deer eat alMost anything in order to have sOMething in the rUMen, but the rUMen Microflora are unable to digest the Material 50 it siMply accuMulates and the deer dies.
41
1.0+
0.9+
0.8+
0.7+
0.6+
0.5+
0.4+
O.3+
O.2+
READ Y-AXIS AS FRACTION DIGESTIBLE
Unbrowsed "first-bite"
__ .n. Browsed "ne;d-bite"
I I I I I I I I I I I +~_______ +1_______ +1 ______ _
I I
I I I
I I +1 _____ - +1 ____ _
+1.0
+0.9
+0.8
+0.7
+0.6
+0.5
+0.4
10.3 I 1°·2 1o.1 I
+'0.0 Bay
berry Blue
berry Red Honey- Red Pitch
Cedar suckle Pine Pine Norway
Spruce White
Spruce
Figure 12. Current forage quality on the Crane areas as indicated by the "first bite-next bite" cOMparisons for eight species.
The average digestibility of the unbrowsed forage is O.31 and of the browsed forage, O.24. These digestibility coefficients are very low; unbrowsed forages with a digestibility of 0.31 are very low quality forages. None of these forages are preferred by white-tailed deer; forage froM preferred species is siMply not available to deer on the Crane areas.
The Magnitude of the decrease in forage digestibilities froM the firstbite twigs to the next-bite after browsing is siMilar to that for red Maple, a preferred browse species, in which the digestibility coefficeints dropped froM about 0.60 at the tips to about 0.45 for the twig portions 12 inches frOM the tips (Moen; In press).
DorMant herbaceous forages collected on the Crane areas had Measured digestibility coefficients averaging about 0.28, which is also very low. The highest digestibility coefficient Measured (0.70) was for apple Mash, which was used in the Crane Refuge to attract the deer for counting purposes.
42
POPULATION PARAMETERS
The estiMated deer population at Crane Reservation and Wildlife Refuge May be described by its age-class frequency distributions, followed by calculations of weighted Mean values for biOMass, ecological MetaboliSM, and forage requireMents. These calculations are weighted according to the fractions of Males and feMales in each of the age classes. Censused nUMbers of deer are alMost always less than the nUMber actually present because not every deer is counted. In this analysis, MiniMUM estiMates of 165 deer on the Reservation and 65 deer on the Refuge have been used as starting cohorts.
Sex and Age-Class Frequency Distributions
Age-class frequency distributions
Male age-class frequency distributions. EstiMates of the percents of Males in six age classes are listed below, calculated with a successiveMultipicatlon equation in the COMputer prograM for calculating an exponential pattern of age class frequencies based on fractions of yearling Males in the population (35.5 and 27.(0) at the beginning of winter as the inputs.
peNT peNT
35.5 27.10
22.3 19.7
14.5 14.4
9.5 110.5
6.2 7.7
11. 6 210.7
FeMale age-class frequency distributions. FeMale age class frequencies are calculated frOM the yearling antler beaM diaMeter (YABO), which is a predictor of reproductive rates and hence potential recruitMent of feMales. EstiMates of the percents of feMales in six age classes are listed below, based on a yearling antler beaM diaMeter of 12 MM.
peNT 26.10 19.2 16.1 110.10 7.5 23.5
Sex ratiOS
Se;~ ratio cl fawns. The Male to feMale fawn se:< ratio (MFFR) is estiMated as a function of yearling antler beaM diaMeter with the equation:
MFFR = 82.8683*YABD A IO.109665
where VABO = Mean yearling antler beaM diaMeter in MM. The relationship between sex ratios of fawns and yearling antler beaM diaMeters is a function of the responses of both Males and feMales to range conditions; poor range results in SMaller antler beaM diaMeters and fewer Male fawns at birth. The predicted sex ratiO, based on a VABD of 12 MM, is 1105.4 Males per 11010 feMales.
Sex ratios of the pre-winter population. The feMale-to-Male population ratio was deterMined frOM the population evaluations of the deer on the Crane Properties. Males Made up 46.3% and feMales 53.7% of the pre-winter population.
4 7 :.J
Weighted Means
EstiMates of biological characteristics using weighted Means which consider the frequency of each of the sex and age classes in the population (Moen 1981a> are used to Make accurate estiMates of population paraMeters. The weighted Mean population characteristics discussed below are based on the sex and age-class frequencies discussed in the previous section. Current-year reproduction was added using the reproductive rates calculated with a yearling antler beaM diaMeter of 12 MM (see Table 5, page 27). Fawn survival rates froM parturition to the beginning of winter were estiMated to be about 74% and 66% for Males and feMales, respectively.
Body weights
Weights of Males and feMales in each age class frOM MaxiMuM to MiniMuM through the winter were used tp deterMine a Midpoint winter weight which was used to derive. the weighted Mean bioMass of the population. The Midpoint weight of each age class was Multiplied by the fraction of the Male or feMale population in that age class and the products sUMMed. Finally, Male and feMale fractions of 0.5 were Multiplied by the weights for each sex. These data are sUMMarized in Table 13.
Table 13. Data used in deterMining the weighted Mean weight of the deer at the Crane MeMorial Reservation and Wildlife Refuge.
Using a 1: 1 se)<; ratiO, the adjustMent--(49*.5)+(40*.5) = 44.5 kg--results in an estiMated weighted-Mean weight -through the winter period of 44.5 kg for the Crane deer populations.
44
Ecological MetabolisM
Ecological MetabolisM of the weighted-Mean 44.5 kg deer was calculated with the following equation and rounded to the nearest 50 Kcal per day:
ELMO = 1.8*70*44.5 A 0.75 : 2150 Keels per day
Forage required
The aMount of dry-weight forage required per day to satisfy the ELMO above is deterMined with the following equation:
FRKD = 2150/(4500*OECO*0.82l.
Using Measured digestible energy coefficients of 0.31 and 0.24 for unbrowsed and browsed forage saMples, respectively, the following equations provide estiMates of forage required in kg per day (FRKD):
FRKD FRKD
2150/(4500*.31*.82) 2150/(4500*.24*.82)
1.88 Kg/day, and 2.43 Kg/day.
These values in kg equal about 4.1 pounds of unbrowsed forage and 5.3 pounds of browsed forage (dry-weight basis) per day. If the deer eat new-growth forage early and are forced to rebrowse later in the winter, the average aMount of forage required per day would be about 4.5 pounds per deer per day, or about 750 pounds per deer for the 5.5 Month period frOM NoveMber 1 to April 15. Reducing this by 10% to allow for the contribution of the fat reserve (see Table 7, page 30 and Figure 8, page 31), about 675 pounds of forage would be required per deer for the winter. Allowing 10% for overestiMations, the aMount of forage required per deer is about 600 pounds; this is considered the MiniMUM estiMate for the winter.
45
46
CALCULATIONS OF CARRYING CAPACITY AND POPULATION SIMULATIONS
Carrying capacity calculations May be Made on the basis of resources required in relation to resources available. In this analysis, nutritive energy is the resource considered, and calculations are Made for the period of plant dorMancy, which is about 180 days.
The nUMber of deer-days supported by the forage available is deterMined with the following relationship:
NUMber of deer-days = forage available/forage required per day.
The nUMber of deer supported through the winter is deterMined with the following relationship:
NUMber of deer = forage available/forage required per deer for the winter.
The nUMber of deer calculated with the relationship above is the carrying capacity; it is the population goal for a given area.
The aMount of forage available has been deterMined frOM MeasureMents on 62 field sites. Forage production patterns in tiMber stands of different ages were illustrated in Figure 4 (page 21), and Measured forage production in pounds per acre is given in Tables 8 and 9. After deterMining carrying capaCity, population siMulations predict changes in the population in response to different COMbinations of natality and Mortality.
Carrying Capacity Calculations
The aMount of forage required per day was calculated in the previous section. Since only part of the current annual growth of woody twigs should be reMoved if plants are to reMain vigorous, deer should be allowed only a fraction of the available growth. A 25% conSUMption fraction has been used in the calculations of carrying capacity in the woodland; this will allow for SOMe recovery of the vegetation on the Crane properties. Since deer are selective when eating herbaceous plants, choosing only the palatable parts of herbaceous plants such as leaf and steM tips, a 4% conSUMption fraction has been used in the calculations of carrying capacity in openland.
Crane MeMorial Reservation
Calculations of the woodland carrying capaCity, openland carrying and COMbined carrying capacity of the Reservation are shown below equations:
WOODLAND: NUMber of deer-days 14527/4.5 3228 deer-days, NUMber of deer 14527/600 24 deer.
OPENLAND: NUMber of deer-days 7184/4.5 1596 deer days, NUMber of deer 7184/600 12 deer.
COMBINED: NUMber of deer-days 2171114.5 4825 deer days,
capaCity, as three
and
and
and NUMber of deer 217111600 36 deer = QOQulation goal.
47
The nUMber of deer supported by the woodland and open land forage cOMbined--36 deer--is the forage-based population goal for the Reservation. This goal provides for proportional use of range forage, and allows for range recovery.
Crane Wildlife Refuge
Calculations of the woodland carrying capacity, openland carrying capacity, and cOMbined carrying capaCity of the Refuge are shown below as three equations:
WOODLAND: NUMber of deer-days NUMber o\' deer
OPENLANO: NUMber of deer-days NUMber of deer
COMBINED: NUMber of deer-days NUMber of deer
5775/4.5 5775/600
3108/4.5 3108/600
8883/4.5 8883/600
1283 deer-days, and 10 deer.
691 deer-days, and 5 deer.
1974 deer-days, and 15 deer = population goal.
The nUMber of deer supported by the woodland and openland forage cOMbined---15 --is the forage-based population goal for the Refuge. This goal provides for proportional use of range forage, and allows for range recovery.
Population SiMulations
ReMoval of deer to reach the calculated population goals was siMulated on a COMputer prograM (Moen unpublished MS.) The prograM calculates the expected effect of reMoval of a fraction of the deer based on the inputs listed in Table 14. The nUMber of deer in each sex and age class is accounted for, agespecific natality rates add fawns each year, and sex- and age-specifIc Mortality rates are calculated as values proportional to Male fawn survival. Population characteristics are calculated at the beginning and end of SUMMer, end of fall, end of a reMoval period, end of Winter, and end of spring.
Inputs used in this population evaluation prograM represent expected responses of the deer populations on the Reservation and Refuge to an iMproving range with population reductions. Thus winter survival increases frOM 0.75 to 0.95 and average Male yearling antler beaM diaMeter (YABD) frOM 12 to 15 over a 5-year siMulation. The increase in YABD results in an increase in reproductive rates in response to iMproving range conditions. Inputs used are described below and nUMerical values are listed in Table 14.
Fawn Survival. An average SUMMer fawn surv,ival of 0.75 is used for each of the five years. This average value is close to the denSity-independent fawn survival value deterMined in an indepth population study in New York State (Moen and Sauer 1977). Fawn survival is largely dependent on the weather conditions during and shortly after parturition. Winter fawn survival is variable, depending on the weather conditions throughout the Winter, and on the forage supply. Increased winter survival inputs frOM .75 to .95 are a reflection of iMproving range conditions as population size decreases. Survival of 95% of the Male fawns through the winter is possible in this coastal area if the habitat is in good condition, as winters are not severe and snow depths are usually MiniMal.
48
Yearling Antler BeaM DiaMeter. As previously indicated (page 27) the YABD is a function of range condition. The fawn sex ratio is related to range condition in the saMe way. Male fawns will survive in greater proportions when range condition is poor. Thus the fraction of feMales in the population will decrease, which in turn decreases the nUMber of reproductively active feMales in the next year. Increasing YABD inputs frOM years 2-4 are again a reflection of iMproving range conditions.
Fraction Qf Yearling Male~ in the Population. This input is used in the equations which generate the starting population in the population evaluation cOMputer prograM. Initial inputs of 0.35 and 0.27 were used, representing populations with SOMe hunting of Male deer and no hunting of Male deer, respectively. Subsequent values of FYMP are calculated based on ManageMent decisions and the results of the annual population siMulations.
FeMale-to-Male ratiO lD the yearling and adult population. This ratio is estiMated on the basiS of herd history. A ratio of 1.00 was used in the initial population siMulations. A ratio greater than 1.00 reflects a higher overall Male Mortality in the general population as a result of hunting.
Equal reMoval rates Qy ~. Equal reMoval rates by sex were evaluated for reMoval rates of 0.30, 0.35, 0.40, 0.45 for the Reservation and for the refuge. These reMoval rates reduced the nUMber of deer on the Reservation to the population goal in 3 to 6 years (Figure 13), and on the Refuge in 3 to 5 years (Figure 14) .
Table 14 .. Population paraMeters used in the population siMulations.
Figure 13. Population reductions in relation to four reMoval rates on the Crane MeMorial Reservation.
50
READ V-AXIS AS NUMBER OF DEER 70 + + 70
+ 60
+ 50
40 + + 40
30 + + 30
20 20
10 -t • .--. •••••• -••••. 10
o +----+----+----+----+----+----+----+----+----+----+ 0 o 1 2 3 4 5 6 7 8 9 10
YEARS
Figure 14. Population reductions in relation to four reMoval rates on the Crane Wildlife Refuge.
After the nUMbers of deer were reduced to the population goals for the Reservation and Refuge, a reMoval rate of 0.15 Maintained the populations at appropriate levels, given the natality and Mortality rates used in these evaluations. These population evaluations were Made with MiniMUM reproductive rates 50 the nUMbers to be reMoved would not be overestiMated. The evaluations need to be updated each year, of course; cOMputer-based inforMation processing is designed for just such purposes.
Two iMportant points that were part of these cOMputer evaluations should be eMphasized here.
1. Reductions in the nUMber of deer were accoMpanied by increases in reproductive and winter survival rates, representing iMproveMent in deer condition and subsequent higher survival and reproductive rates (See Table 14, page 49),
2. The nUMbers of deer that les5 than the nUMber expected to populations on these two areas are
should be on the Reservation and Refuge are die frOM starvation each year if the deer allowed to level off "naturally."
51
52
MANAGEMENT OPTIONS
ManageMent options May be evaluated by siMulations which represent deer populations and predict population trends without the expense and delays associated with actual trials. This is analagous to financial analyses which May be cOMpleted for different rates of return; actual rates May not be known in advance, but various options and expectations are considered when Making decisions. In this report, the de~r population has been described with the best available current data, and the expected effects of different ManageMent options are discussed next.
Do Nothing
One ManageMent option is to do nothing, to let "nature take its course," Man, by virtue of land use patterns that have developed for several centuries on the East Coast, has Made it iMpossible for nature to take its course, ecologically. Since predator-prey populations such as wolves-deer cannot exist in the tiny Crane properties (Much SMaller than the territory of a wolf pack) as they do in the four-Million acre Superior National Forest in Northeastern Minnesota, for exaMple, or as wolveS-Moose do on Isle Royale National Park in Michigan, a "do nothing" approach to d~er population ManageMent on the Crane properties results in a deer population 50 high that understory abundance, diversity, and COMposition is controlled by deer. That population level has already been reached.
The deer on the Crane properties are physically in poor condition and Many starve to death there; eighteen were found dead frOM starvation during the past winter. Necropsy reports COMpleted at Tufts Veterinary School describe the carcasses with such words as "eMaCiated, depletion of fat, chronic inanition, and gelatinous bone Marrow." Dead fawns have ranged in weight frOM 37 to 55 pounds and averaged 46 pounds at death, which is the predicted weight-of-no-ret~rn of fawns (Moen and Severinghaus 1981). RUMens of the dead deer have been filled with coarse plant fiber Material, Marsh grass, and pitch pine needles; one rUMen saMple analyzed had a Measured digestibility of only 17%.
Since there are no predators on the Crane properties to reMove the weaker deer as there are in large natural systeMS, ecological relationships are not COMplete. The ecology of this area is dOMinated by Man, and this will continue to affect aniMal--environMent relationships until the hUMan population gives up the land and departs, allOWing it to revert to COMpletely natural conditions. That is not planned for in the near future, of course.
Feed the Deer
It is teMpting to consider feeding deer which are starving. While it seeMS like a solution to a probleM, it cOMpounds the probleM of too Many deer for the carrying capaCity of the land. A successful feeding prograM would result in higher survival rates, which would result in a higher population growth. Increases in the nUMber of deer would result in More iMpact on the habitat, and feeding would have to be continued until the population were reduced. Whenever there are too Many deer for the habitat to support, SOMe Method of herd reduction is necessary.
53
There are several practical probleMs associated with feeding deer. One, as rUMinants, deer need tiMe for the Microflora in the rUMen to adjust to new feeds. Thus changes in diets Must be Made over a period of tiMe. Two, feeding concentrates the deer, and this increases the likelihood of exchanges of parasites between deer. Three, costs of feeding an increasing deer herd becoMe higher as the deer becoMe More dependent on food supplied artificially. The only reasonable place for a deer-feeding prograM is in a deer park, an area dedicated to the raising of deer. Then, diets can be carefully controlled and proper veterinary attention given as necessary. Such deer parks Must have plans for control of herd sizes, of course. The Crane Reservation and Refuge are not deer parks.
Reduce the Population
The Crane Reservation and Refuge are clearly overpopUlated with deer, and plans for the reduction of population size should be Made as soon as possible. Several Methods should be considered to start with, for the population is high enough to deMand iMMediate attention and intensive reduction. Considering the nUMber of deer present, a five-year plan May well be needed to get the population down to carrying capacity, and this plan should be iMpleMented and the results Monitored by an aniMal control specialist (see page 55). Several Methods for population reduction are discussed briefly next.
Trapping
Trapping deer is a labor-intensive and capital-intensive activity that yields Mixed results. It is expected that initial trapping efforts would be· quite successful, relatively speaking, but would beCOMe increasingly difficult as the population was reduced. It would be both difficult and costly to reduce the deer population on the Crane areas by trapping; the various traps described in Rongstad and McCabe (1984) are useful for specialized experiMental applications but not for popUlation control.
Regulated hunting
RegUlated hunting, with predictable nUMbers of aniMals reMoved during a prescribed tiMe period, can be an effective population control Method. Different forMats May be used, as discussed below.
Public hunting. Public hunting on the Crane properties, open to anyone holding a valid license, would not be siMilar to public hunting on large acreages since the area is SMall, and the deer are accustOMed to hUMan activity_ While the deer would qUickly beCOMe More elUSive, the SMall size of the Crane properties and the unique features they contain Make an open-to-thepublic hunt less desirable than More highly-regulated and controlled hunting.
Controlled hunting. Controlled hunting iMplies the presence of selected hunters, screened for their abilities to handle firearMS safely and accurately. Such a hunt would be More appropriate on the Crane properties than a public hunt Since nUMbers and locations of hunters could be carefully controlled. Experience with such controlled hunts at the Carey ArboretUM i~ New York State has shown that aniMal control beCOMes More successful with each paSSing year as experience is gained by both ManageMent and the roster of hunters.
54
Quota hunting. A goal-oriented reduction prograM could be set up on a trial baSis on the Crane properties, with reduction continuing until a designated quota has been reMoved frOM the population. This reduction would be carefully Monitored, with each aniMal inspected and its sex and age entered into a population prograM in the cOMputer which would continually update the predicted requireMents of the herd reMaining on the land, the reproduction expected at the next parturition, and the iMpact of these changes on next years population. Quota hunting is ideally suited to critical and highdaMage areas such as nature preserves, arboretUMS, orchards, and truck farMS. Quota hunting ensures adequate reMoval, MiniMiZing the possibility of probleMS due to overpopulations recurring frOM year to year. The use of electronic inforMation processing Makes quota hunting and siMultaneous predictions of subsequent population dynaMiCS a distinct possiblity; such a COMputer prograM is analagous to "interest cOMpounded daily" financial prograMS. The difference is that we are dealing with a population of deer rather than dollars; both populations consist of deposits (births) and withdrawals (deaths). A cOMpound interest rate as low as 10% results in a doubling of the account in less than 10 years. Deer populations generally aCCUMulate at rates Much higher than 10%, and withdrawals are necessary to Maintain an appropriate balance.
AniMal Control Specialist
The nUMber of deer on the Crane properties in relation to the nUMber that should be there based on forage conditions is so great that population reductions are necessary for the sake of both the aniMals and their habitats. This is a COMMon probleM with Many wild aniMals; daMage control is a significant probleM in Many areas (Decker 1983).
An aniMal control specialist could be given the responsibility of keeping aniMal populations on the Crane properties under control. Woodchucks, for exaMple, could hardly be allowed to dig dens just anywhere on the lawns. Rats and Mice can be probleMS in old and new buildings. Deer have obViously affected ornaMental plantings around the Great House. An aniMal control specialist would have the responsibility of developing a prograM for the control, both in nUMber and distribution, of all species which have caused probleMS in the adMinistration of prograMS within the responsibilities aSSUMed by The Trustees of Reservations. This person would be responsible for planning and Managing the deer reMoval prograM, including the quota-hunting prograM, if that were iMpleMented. The larger role of the aniMal control specialist is discussed further on page 83.
55
56
ECOLOGICAL CONSIDERATIONS
AniMal and environMent are inseparable and interactive; the status of one affects the status of the other. Many ecological considerations need to be Made when analysing aniMal and environMent interactions. In this report, attention is directed toward natural area considerations, population interactions, and population potentials for growth and environMental iMpacts. These are discussed next.
Natural Areas
Natural areas are ecological unit~ having particular size characteristics that allow both plants and aniMals to live in with one another. There are few totally natural areas left states; considerations Must be given to recovering areas which
and diversity dynaMic balance in the United are not too far
reMoved frOM their natural conditions. diversity--are discussed next.
Two Main considerations--size and
Size considerations
Land areas Must be of sufficient size for ecological relationships to develop before such an area can be considered "natural." Thus a SMall area used by a population for only part of the year or for only part of the aniMal's needs (shelter but not food, for exaMple) cannot be considered a natural area for that species. "Naturalness" is a function of biological characteristics and ecological relationships; it is not a function of legal classification, ownership, or intent of the owners or other interested parties.
Diversity
Natural areas Must, by definition, contain enough diversity of plant and aniMal life for ecological relationships betuleen these two Major COMponents of an ecosysteM to develop. Such diversity develops only when no single COMponent or few COMponents dOMinate the area. Diversity in plant COMMunities, for exaMple, is Maintained when natural forces are allowed to operate. Fire, for exaMple, is necessary for the Maintenance of tallgrass prairie (Henderson 1982). Decadence of trees due to old age results in windthrows and openings in the canopy, which result in an understory response to light. Such natural events are usually not allowed to occur in areas used intensively by different segMents of SOCiety; fires are put out, windthrown trees are often reMoved, and other Modifications are Made to the environMent.
The Crane properties have been subjected to a high degree of Man-Made Modification, which was an iMportant reason for The Trustees of Reservations assuMing ownership of these properties. The properties do not, at this tiMe, contain the natural diversity of plant and aniMal life characteristic of this general area. With proper restoration and ManageMent, SOMe of the natural diversity can be restored.
57
Population Interactions
Natural and dynaMic interaction between aniMals and their environMent is a Most desirable alternative for natural areas. Unfortunately, areas as SMall as the Crane properties, surrounded by about 300 parcels of agriculture, forest, recreation and tax-exeMpt land, plus an unknown nUMber of residential parcels in the town of Ipswich, do not support the full COMpleMent of native fauna necessary for the Maintenance of natural, dynaMiC balances. Predators of large herbivores are either absent or not abundant enough in such areas to have an iMpact on present deer populations. Deer, wolves, lynx, and wildcat were reported to have disappeared frOM Massachusetts by the Middle of the 19th century (Thoreau 1866). The deer populatirin has recovered, but wolves and lynx have not, nor are they likely to in the future. Coyotes are not abundant enough to iMpact the deer population. Thus we hUMans, responsible for Major alterations in balances between natural predator and prey populations, Must aSSUMe SOMe responsibility for the welfare of the wildlife species with which we share the land.
Predator-prey interactions
Predator-prey interactions are SOMetiMes expected to result in a "balance of nature." The balance of nature is very dynaMic, however, and cyclic fluctuations in prey populations are followed by siMilar fluctuations in predator populations (Peterson et al. 1984). Cycle periods are apparently related to body size of the prey; Peterson et al. have derived an eMpirical equation for calculating cycle period as a power function. The equation is:
where CPDY LWTK 0.26
[0.23-0.29J
CPOY = 8.15*LWTK A O.26[O.23-0.29]
cycle period in years, live weight in kg, the power function exponent, and the power function exponents for the 95% confidence interval.
Thus the cycle period of a deer population with LWTK = 50 is predicted to be 22.5 years [20-25 years]. The predictability of such cycle tiMes is dependent on the naturalness of conditions in the habitat. Open systeMS, in which deer are allowed to Move in and out, should not be expected to conforM to such predictions because aniMal welfare is partly dependent on external factors.
Open-closed systeMS
One requireMent for an area to aSSUMe its own natural (but dynaMic) balance between aniMals and environMents is that the systeM be closed, not subject to significant iMpacts by iMMigration or eMigration. If this is not the case, then characteristics of adjoining and interMingling populations will affect characteristics of the population in question. The extent to which interMingling occurs is dependent on the size and shape of the area which affect the aMount of boundary between populations, the Mobility of the aniMals, and the sizes of territories and hOMe ranges used by these aniMals. Since the aMount of boundary declines as area increases and territory and hOMe range sizes of different species are known, this relationship can be calculated. The theoretical basis for this is illustrated in Figure 15 where the cirCUMference of a circle does not increase as rapidly, or in direct
58
proportion to increases in the area of the circle. relatively less as the circle size increases.
The circuMference beCOMes
Figure 15.
V-AXIS CIRCUMFERENCE IN THOUSANDS OF FEET 6 6
5
4
3
1
o +----+----+----+----+----+----+----+----+----+----+ 0 o 1 2 3 4 5 6 7 8 9 10
AREA IN SQUARE MILES
As the area of a circle increases the cirCUMference relatively less. This is part of the theoretical MiniMUM sizes of natural areas required to MiniMize froM adjoining areas.
increases basis for influences
The susceptibility of habitat islands to invasion by shade intolerant edge species I~hich thrive in the interface between habitat islands and the surrounding landscape is discussed by Guntensperger (1983). While Mentioning the need to". consider patch and landscape dynaMics as well as the natural history characteristics of the cOMponent species. .," discussions by Guntensperger of invasions and their iMpacts on the natural vegetation are liMited to plants. The iMpact of herbivores is usually overlooked until their populations reach critical levels, as in grass hoper plagues which strip the vegetation and MaMMalian herbivores, sMall and large, which iMpact plant establishMent, growth and reproduction.
terrestrial areas set aside as nature preserves, systeMS, are surrounded by landscape dynaMiCS which variable, dynaMic, and often unknown ways. Such open systeMS, with the aMount of openness very Much
Thus legally-defined often thought of as closed influence the preserves in preserves are biologicqlly dependent on area size, characteristics of the aniMals
habitat dynaMiCS, and the natural history using the areas.
59
Population Potentials
How fast can deer populations grow? Using exponential predictions of population growth described in Moen (1981) for deer populations with an equal sex ratio as an approxiMation, a population of 100 deer (50 Males and 50 feMales) with a reproductive rate of 0.80 (the current weighted Mean reproductive rate for the Crane properties), and no Mortality would increase to 538 deer in 5 years. Does such an increase sound iMpossible? If you deposited 1100 in the bank at 10% interest, you would have 1110 at the end of one year and 1161 at the end of five years, cOMpounded annually. The saMe algorithM was used for calculating the nUMber of deer after five years; only the interest rate was higher as the deer reproduced at a rate of 80% per feMale.
The 5-year deer population potential given above would not occur in nature because Mortality reduces the population during each year. A realistic but siMplified exaMple of deer population growth is discussed below.
Population growth
Deer populations have a very high potential for growth, even in the presence of Mortality since adult feMales in good condition usually bear two young each year, and fawns May breed when they are only 6-7 Months old, resulting in Many generations of deer in a population. Thus deer Multiply, and populations are held in check only by Mortality.
Using the exponential algorithM for predicting population growth Mentioned above, an estiMated 250 deer on the Crane properties with a weighted Mean reproductive rate of 0.8. would increase to 440 deer in five years if total Mortality were 20%, or 50 dead deer per year froM the initial population and 88 dead deer froM the fifth-year population. If Mortality increased to 30%, 250 deer would decrease to 225 in five years. Then, 75 deer would die froM the initial population and 68 froM the fifth-year population, an average of about 70 deer per year. These nUMbers of dead deer are greater than the nUMber of deer that should be present on the Crane areas, based on the carrying capacity of the forage resources. The large nUMbers of deer present on the Crane properties and the substantial nUMber of deaths necessary to stabilize the population can both be reduced by careful and prudent ManageMent.
Persistence over tiMe
Deer populations can perSist on overbrowsed range at levels that seeM iMpOSSibly high in relation to the aMount of food available. This is possible for two Main reasons. One, deer take advantage of plant growth in the SUMMer to reach MaxiMUM weights during the annual cycle in the fall, providing a fat reserve that contributes to the likelihood of survival through the winter. The relative contributions of fat to the Metabolic requireMents of different age classes were illustrated in Figure 9 (page 31); note that older deer have a distinct advantage over younger deer in this regard. Two, a population will reMain high if annual losses are replaced by annual increMents. If a feMale deer, with a natural life expectancy of 12 years has 10 years of reproduction, only one feMale fawn need survive to breeding age to replace the original feMale. With an approXiMate 1:1 sex ratio at birth, this represents only two surviving fawns, one of which is feMale, out of 10 years of reproduction. A
60
feMale deer in good condition should give birth to 15 or More fawns in 10 years, so prebreeding-age Mortality can be as high as 80% (three fawns live and 12 or More die) and yet a population could perSist. Such a theoretical upper liMi t is not expected in the wild each year because of the effects of other factors, b u. t it is part of the explanation for deer populations persisting at incredibly high levels for Many years in areas with severely overbrowsed forage resources.
EnvironMental iMpacts
Large herbivores such as deer have the potential to alter the COMpOSition of the habitat, causing a reduction in the abundance of More-preferred plants (these plants are called decreasers) and an increase in the abundunce of lesspreferred plants (these plants are called increasers).
White-tailed deer have literally taken control of the understory on the Crane properties. Browse lines have resulted froM excessive foraging throughout the areas. Honeysuckle, a high-fiber plant with low digestibility, increases even though it is heavily browsed. Its fine twig structure--Most twigs are less than one MM in diaMeter-- Makes it hard for deer to conSUMe each tWig, so enough twigs escape foraging for the plant to Maintain itself, even though its shape is altered by the deer. Its abundance and response as an "increaser" was striking under conditions of new leaf growth and full flowering phenology.
Plants with twigs having diaMeters of several MM, such as pitch pine, sugar Maple, and apple, are essentially 100% browsed by the end of winter; virtually every twig on preferred forage species that was within reach of deer had been browsed by April, 1984.
SOMe herbaceous plants are Much less abundant than expected in areas where deer have foraged intensively. There was an alMost COMplete lack of spring wildflowers in the stands of trees on the Crane areas in early June, 1984. TrilliUMS and violets were conspicuously absent, probably as a result of the deer foraging on theM over the years. TrilliUM flowers weigh about 0.1 gM each and the top part of the plant about 0.25 gM each, so hundreds are needed to satisfy even a very SMall part of a deer's daily requireMent.
Photographs illustrating SOMe of the environMental iMpacts of deer on the Crane MeMorial Reservation and Wildlife Refuge are described on the photo-page inserts which follow on pages 63-70.
ManageMent of the habitat and nUMbers of different species is suffiCiently weIr-developed as an art and science to prevent such environMental iMpacts, and to provide not only for the presence but also an appropriate abundance of both plants and aniMals, native and introduced. The Trustees of Reservations has the opportunity to restore natural diversity and historic diMensions to the Crane properties as long as ManageMent options are retained and ecologically responsible decisions Made.
61
62
THE PHOTOS ON THE FOLLOWING PAGES ILLUSTRATE SOME OF THE IMPACTS OF DEER ON THE CRANE MEMORIAL RESERVATION AND WILDLIFE REFUGE
Photo 1. A newborn white-tail fawn on the Wildlife Refuge. Fawns weigh about as ~uch as a hUMan baby at birth, and feMale deer weigh about as Much as an adult WOMen. Yat deer have the capacity to grow frOM suckling fawns to breeding feMales within a few Months, giving birth to their own young when they are just one year old. Thus a 12-year-old doe could be a great, greai, great, great, great, great, great, great, great grandMother!
. - 0 t a b-,OW5 P line by reaching up for forage; distinct browse Photo~. eer crea e - -- .
7 ~ • -~5~u~e or~ ~ larne nUMber of deer. lines result frOM the neavy ,oraglng p, ~ ~ , ~ ~
63
Photo conifer nab! tat.
Much of the Crane Wildlife Refuge is covered with plantation, a striking feature on the skyline but
a very
50-year-old poor deer
Photo 4. Meadows of Mixed grasses and forbs and a honeysuckle shrub COMMunity Make up the reMainder of the Grane Wildlife Refuge.
Photo S. ,"e browse line 15 very distinct throughout the Refuge.
It,g~~~~:i;~f~:~~~.-Photo tI. Some or the 55 or More deer which winter on ihe Refuge.
Photo 7. Walter Prisby, Refuge Manager, hand-reeding a deer.
Photo B. Two deer en the Refuge, the overpopulation has created.
standing front or the browse line which
65
Photo 9. A honeysuckle shrub that has been heavily browsed by the deer, Doth winter and SUMMer.
Photo 10. Honeysuckle leaves and flowers out of reach of the deer.
Photo 11. This branch has been browsed heaVily and is alMost dead. Photos 10 & 11 were both taken in june, 1984.
56
Photo 12. There is essentially no forage the conifer canopy on the Refuge.
Photo 13. A spruce tree has been partially protected froM browsing with wire netting.
Photo 14. Shrubs at the Crane gravesites ~ust protected froM browsing by deer.
Photo 15. 80th the Reservation and Refuge have salt Marsh habitat adjacent to the uplands.
Photo 16. An ornaMental Mugo Pine in front of the Great House has been heaVily browsed by deer.
Photo 17. An apparently dense understory is deceiving with reference to deer habitat; this is priMarily honeysuckle, which is poor deer forage.
58
Photo pines Neck.
18. Wooly hudsonia (foreground) and cover parts of the sand-dunes on Neither are good deer forage.
Photo 18. A heavily-browsed shrub against snow froM a late-winter storM, March 1984.
Photo 20. Pitch pine was heavily browsed by end of March, 1984.
59
Photos result plants winter,
21 & 22. Browse lines are evident everywhere on the of foraging in both winter and SUMMer. Not only is within reach of the deer reduced due to the heavy but SUMMer browsing is unusually severe.
70
Crane areas as a the vigor of the browsing in the
LEGAL, SOCIAL, AND ECONOMIC CONSIDERATIONS
ManageMent of free-ranging populations of wild species is accoMplished best when the biological relationships between aniMal and range are understood first. Then biologically-based ManageMent objectives can be established, and legal, social, and econoMic considerations Made. We hUMans share the land with wild species, and careful consideration of the Many diMensions involved in land use will result in reasonable nUMbers and resource use by all species.
Legal Considerations
Relationships between Man and aniMals are governed by laws prohibiting cruelty to aniMals, regulating the taking of aniMals, and allowing for daMage perMits for control of protected species when they iMpact agricultural production. Very brief discussions of these considerations follow.
Cruelty to AniMals
Paragraph 77 in "Annotated Laws of Massachusetts" addresses the issue of cruelty to aniMals. Written priMarily for the protection of dOMestic species, the law pertains to « owner, possessor, or person having charge or custody of an aniMal. .,. and provides fines for unnecessary tortures, suffering or cruelty of any kind ... "
Hunting regulations
Hunting regulations May be written which will control deer populations without extirpating theM, and hunting is a cost-effective Method of population control (Giles 1978) under SOMe cirCUMstances. The nUMbers of deer that should be reMoved froM a population each year can be predicted with Much More precision now than at any tiMe in the past as electronic inforMation processing allows the biologist to evaluate the cOMbined effects of natural and regulated Mortality on population growth. In areas where deer populations are high and the potential for daMage or disease critical, quota-based hunting, with legal hunting perMitted until a prescribed nUMber have been reMoved, will result in better control of deer nUMbers than the issuance of a specified nUMber of licenses to take deer during a predeterMined tiMe period.
DaMage PerMits
DaMage perMits are often issued whenever deer cause or have the potential for causing daMage to agricultural crops. The use of daMage perMits, which extend the tiMe for reMoval of deer, is another forM of a quota-oriented harvest rate. It has been used in retrospect; perMits are issued after COMplaints are filed. The science and art of population control has now reached the point where probleMS can be prevented rather than cured, and that is a fundaMental characteristic of good ManageMent of any resource.
71
Social Considerations
EnjoYMent Qf Nature
EnjOYMent of nature is an alMost universal hUMan trait. Kinds of enjoYMents are Many, however, and often COMe into conflict. Those wishing to see a large nUMber of wild aniMals abhor the thought of even one of theM being deliberately reMoved froM a population. Those wishing to see a large nUMber and diversity of plants are upset when excessively high aniMal populations cause Modifications of the plant COMMunity. Nature is not liMited to wild plants and aniMals, however. OrnaMental shrubs and vegetable gardens are planted as part of our Unatural" hUMan existence, and these can be severely iMpacted by deer when populations of these adaptable herbivores are high. It is iMportant to realize that nature has Many diMensions, and the interrelationships aMong theM Make singe-objective ManageMent plans unrealistic, except in the MOSt reMote wilderness areas where one Might siMply "let nature alone" COMpletely, which Means no hUMan activities, no fire suppression, no reMoval of anything frOM that part of the earth. It is desirable and even necessary to have such areas, but the Crane MeMorial Reservation and Wildlife Refuge on the eastern coast of the United States do not fit the criteria for such ManageMent.
AlMOst everyone enjoys seeing wildlife, or SiMply knowing that "it is out there." Wildlife are enjoyed by Many people More in the abstract than in reality. The thought of grizzly bears roaMing parts of the reMote west is More enjoyable if close friends have not been MaiMed or killed by theM. The thought of white-tailed deer roaMing the Crane properties is More enjoyable if the deer have not caused a friend to be in a vehicular accident, if they have not destroyed a new and expensive planting of shrubs around your house, if they have not killed young apple trees in your orchard, or LYMe disease has not been contracted by you or a faMily MeMber. Direct contact with excessively high deer populations changes peoples attitude toward deer, though fortunately not to the point where COMplete eliMination of populations is called for; reduction of deer populations to nUMbers within the carrying capacity of the habitat ,is usually sufficient.
~ disease
Periodic occurrences of what is now known as LYMe Disease or LYMe Arthritis have been reported since 1909. The first reported case in North AMerica was in a Wisconsin resident in 1970 (ScriMenti 1970). The disease was naMed after a 1975 outbreak in the town of Old LYMe, Conneticut. There, several children had arthritic SYMptOMS, but the cause could not be identified. Discussions by the Mothers of the children led to the realization that the sick children had been bitten by ticks. Thus the source of the disease was identified and the epideMiology has since been described in detail.
The original European naMe for LYMe disease was "ErythreMa chronicuM Migrans" (ECM). SYMptOMS have been described under several naMes, including Bannworth syndrOMe, tick borne Meningal, chronic Meningitis, active derMatitus, aMd lYMphocytoMa. Disease SYMptOMS develop one to two weeks after exposure. Initially there is an expanding ringlike rash, generally aCCOMpanied by Malaise, fatigue, headache, and fever and chills. SOMe patients suffer Musculoskeletal pain and SYMptOMS of Meningeal irritation.
72
Secondary skin lesions, annular red blotches and circles, diffuse erytheMa, and urticarial rash May occur. COMplications, including heart block, Bell's palsY, and cranial neuritis can develop with a lag tiMe of weeks to Months. Recurrent interMittent polyarthritis affects Many patients (SpielMan et al. 1984). TreatMent with antibiotics such as tetracycline and penicillin can reduce the duration and severity of later SYMptOMS, and early treatMent increases the effectiveness of the antibiotic. The best Method for preventing acquisition of LYMe disease is to avoid areas where the tick is present. An attached ti~k should be reMoved as soon as possible, since there May be a lag tiMe of several hours frOM tick attachMent to tranSMission of the disease (SpielMan et al. 1984)
The disease is apparently caused by a spirochete (Anderson et al. 1983), and the deer tick, Ixodes daMMini, has been iMplicated as the vector. Presence of ~ daMMini is essentially dependent on the presence of deer. ,Ixodes daMMini is a three-host tick, and spirochetes have been found in the larval, nYMphal, and adult stages of the tick in Conneticut. The larval stage feeds on SMall and MediUM-sized MaMMals, birds, deer, and hUMans. The nYMphal stage tends to be found on large MaMMals, but occurs on SMall MaMMals as well. 80th larval and nYMphal stages are found MOSt abundantly on the white-footed Mouse, PeroMYscuS leucopus. Adult ticks feed on MediUM to large size aniMals, priMarily due to their habit of residing on the vegetation about one Meter off the ground, waiting for a host to COMe by. White-tailed deer, a large and SOMetiMes locally-abundant MaMMal in the Northeast, is a priMary host for the adult ticks.
LYMe disease occurrs in the Northeast only where the deer tick is present. One of the highest known populations of the deer tick is the Crane Beach Reservation (SpielMan et al. 1984), and evidence now indicates that there is a direct relationship between the abundance of ticks and the abundance of deer (Unpublished preliMinary results, Harvard School of Public Health).
AtteMpts were Made, in a 1982 study on Great Island, Cape Cod, Massachussets, to decrease the availibility of deer to ticks (Wilson and Levine 1984). First, atteMpts were Made to trap deer and treat theM with acaricide or insect repellent. None of the Methods used to trap the deer, including corrals, nets, and box traps, were satisfactory. Tranquilizing the deer at night with rifles was the only effective Method of capturing the deer, but then, the acaricides and repellants did not work well on the deer. It was finally concluded that nondestructive Methods to reduce deer availiblity to the tick had failed, and deer were reMoved with rifles.
Recent social chanoes
The question of why there are More deer probleMS now is often raised, and indeed questions were raised about why there is a high deer population and More probleMS now at the 3/28/84 Meeting of the advisory group (see pages 8-9). It is not known just how Many More deer there are now than in previous years, but the general iMpression throughout North AMerica and Northern Europe is that wild rUMinant populations have been increasing in Many areas in recent years. Rather than dwell on such large-scale trends, let us look at changes in the nUMber of people in the town of Ipswich during the last 35 years. Since More people in an area result in More contacts with deer, even if the deer population reMains stable, the nearly two-fold increase in the population
73
of Ipswich since 1950 (Figure 16) is a Major factor in calling attention to deer-huMan interactions.
READ Y-AXIS AS THOUSANDS OF PEOPLE 12 + -., ... -----~.-
.~.
+ 12
10 + + 10
8 + + 8
6 + + 6
4 + + 4
2 + + 2
o +----+----+----+----+----+----+----+----+----+----+ 0 1950 1960 1970 1980 1990
YEAR
Figure 16. The population of Ipswich, the town in which the Crane properties are located, has increased froM about 6900 in 1950 to about 11500 in 1984.
Ipswich May appear to be a qUiet rural area to persons living in the city, but the density of houses throughout the Town is high when considering the potential for deer contacts. Argilla Road, which leads froM the South Green of Ipswich to Castle Beach, has More than 100 residential sites on the 3.5 Miles of road frontage between the Crane areas and Hearthreak Road. In the first two Miles alone there are More than 50 dwellings, a horse farM, and an orchard. The situation is even More dense than the nUMbers indicate because of the aMount of salt Marsh which is adjacent to the road in the first 1.5 Miles frOM the Crane properties.
One other factor--the overall state of the econOMY-- enters into evaluations of deer iMpacts on hUMan activities. When the econOMY is tight, the iMpact of deer and other Wildlife, as well as any unplanned-for iMpact on one's business or property, lOOMS relatively greater than in tiMes of econoMic prosperity. Further, an established orchard grower who has experienced SOMe deer daMage over the years but has adjusted ManageMent and pricing to accoModate such daMage has a different relationship to deer than a new grower who has recently purchased an orchard, Makes plantings of new varieties, and then experiences a high level of deer daMage. It is difficult for persons not faMiliar with deer and their habits to anticipate the potential for deer daMage when evaluating orchards prior to purchase and planting, as eVidence of· deer daMage and the potential for daMage is often subtle.
74
EconOMic Considerations
The econoMic value of deer and their iMpact on the f'ange is hard to Measure because no single MeasureMent unit is available to Quantify value. How does one Measure the value of seeing a deer, a value which varies between people and fluctuates due to cirCUMstances. SOMeone seeing their first deer in the wild places a high positive value on the experience, while SOMeone who has just had a new car daMaged in a collision with a deer places a high negative value on seeing another deer. The value of gold, a precisely-defined resource, has varied, worldwide, by about a factor of two during the past year or two. In COMparison, the value of deer varies by an alMost infinite aMount, depending on our past experiences with theM. Rather than trying to quantify the value of deer, brief discussions of SOMe econOMic considerations of the effects of deer follow.
DaMaae to property
Two Main kinds of property daMage by deer occur: daMage to plants and daMage to vehicles. DaMage to plants ranges frOM killing of new plantings, such as orchards and ornaMentals, to Modifications of the structure of natural plant COMMunities. DaMage to orchards can be extensive; seMi-dwarf apple trees have only about 10 new twigs after their first year of growth in the orchard, and each twig weighs only a fraction of a graM. Thus a few deer can destroy hundreds of apple trees in a few days in late winter and spring (Moen 1983). OrnaMental plantings around a house can cost several hundred to a few thousand dollars, and deer have the capability of severely iMpacting and even destroying such new plantings. While deer appear to be afraid of Man in the Wild, they readily COMe up to houses and feed on gardens and shrubs during the night, especially in late winter and early spring. The probleM is cOMpounded when the deer are More accustoMed to hUMans, as happens in protected suburban populations.
Vehicular daMage frOM collisions with deer' can range frOM Minor dents to Major daMages and even death to occupants of the vehicle. There are Many variables involved, of course, including speed of travel, weight of the deer, kind of vehicle, and the response of the driver.
Protection frOM daMace
The costs of protecting ones property frOM the iMpacts of deer varies with the kind of protection used and the aMount of property to be protected. Low-cost Materials and devices which eMit cheMical, Visual, or auditory signals are alMost always ineffective when deer populations are high. The best protection is a substantial fence about eight feet high, and such fences cost about $4.00 per linear foot to install. Thus protection of a yard and garden 50 feet square, with 200 feet of periMeter, would cost about $800.00. The cost is high, but even More objectionable is the appearance of such a fence; we can beCOMe prisoners of deer in our own backyards. Further discussions of wildlife daMage May be found in Decker (1983), McAninch et al. (1983), and Moen (1983a and 1983b).
75
Medical treatMent ~ recovery
EstiMates of the costs of Medical treatMent and recovery froM interactions with deer, including injuries sustained in vehicular collisions and froM contracting LYMe disease are not available, but the nUMber of collisions and cases would result in substantial dollar costs for treatMents, and additional substantial costs due to lost work tiMe and the psychological effects associated with treatMent and recovery. The fact that these costs have not been quantified does not negate their existence; reality Must be faced and appropriate cost accounting recognized. Excessively high deer poplJlations are not benign.
76
MANAGEMENT RECOMENDATIONS
ManageMent of the deer populations on the Crane MeMorial Reservation and the Crane Wildlife Refuge presents opportunities to consider a variety of techniques to first reduce the population and then to control it. ManageMent is clearly necessary; the Crane properties are not wilderness areas, nor can any COMpleMent of predator-prey populations reMotely reseMbling wilderness conditions ever be restored on these areas. The hUMan population and land uses in this part of Massachusetts have altered natural conditions for over 350 years, and never in its history has this area been so intensively used by hUMans as it is now. As a SOCiety, we have the responsibility to recognize our effects on both plant and aniMal populations, and to Manage both of these natural resources accordingly.
It Must be recognized, when considering these ManageMent reCOMMendations, that the Crane areas are open to MoveMent of deer in and out, so ManageMent of deer on adjacent properties affects characteristics of the deer populations on the Crane areas. If deer were COMpletely protected in the towns of Ipswich and Essex, then The Trustees of Reservations would be in an alMost iMpossible situation. Currently, two deer May be taken during the specified 9-day hunting season in the Ipswich area, subject to the follOWing condition, posted on the town line as one enters IpSWich on Highway 133:
Notice Hunters Town of Ipswich Closed to Hunting Except by Written PerMission of Landowners Violators Subject To Prosecution
Police Dept.
If enough landowners do not allow deer hunting on their properties, then the deer population will reMain high and the potential for property daMage and habitat degredation will reMain great.
The population of 230 or More deer using the Crane areas in the winter is about five tiMes higher than it should be if relicts of both natural vegetation and ornaMental plantings are to be restored. Further, the deer are physically in poor condition, indicated by the large nUMber of fawn deaths due to Malnutrition in a coastal winter environMent which is relatively Mild cOMpared to inland areas where colder teMperatures and greater snow depths are endured by deer in good condition. Thus the first ManageMent decision to be Made by The Trustees of Reservations is whether or not the deer popUlation will be reduced in consideration of the condition of both the habitat and the deer. If the population is reduced, then control Measures will be necessary in order to keep the nUMber of deer within liMits which will allow for the recovery and restoration of the vegetation. A position with the general title of "aniMal control specialist" is suggested to oversee a reduction and control prograM initiated by The Trustees.
77
AniMal control specialist
The probleMs associated with reducing a deer population from such a high level, the length of time needed to reduce the nUMber of deer, and the need to evaluate the ManageMent strategies iMpleMented Make it MOSt desirable to have a personnel position established to Maintain records and provide continuity to the prograM froM year to year. Preventive Measures are always better than corrective ones, and Many potential problems resulting from the presence of wild aniMals on areas used as intensively by the public as the Crane areas can be avoided with proper planning. The aniMal control specialist May need to consider several aspects of deer herd reductions in the iMMediate future, depending on the options chosen by The Trustees of Reservations.
A distinction between population reduction and population control Must be Made clear at this point. Population reduction, a corrective measure, is used I~hen the nUMber of deer on an area exceeds the nUMber that should be present if both the animals and their habitats are to be in good condition. ReMoval Must exceed annual increMents to a population in order for a population to be reduced. Population control is used when the nUMber of deer is in reasonable balance with the habitat resources, and the nUMber is kept at an appropriate level by reMoving a number of deer which is about equal to the annual increMents to the population.
The aniMal control specialist should be given the responsibility of overseeing population reduction and control prograMS. This will include collecting data on the deer at the Crane areas, keeping records of nUMbers seen and their sex and age identified whenever possible, measuring weights, collecting rumen contents and forages eaten, etc. These data will be of value when COMpleting additional evaluations of deer and range conditions. The discussions below pertain to population reductions, followed by discussions of popUlation control.
Population Reduction
Deer popUlation reductions are desirable when both animal and habitat conditions have deteriorated because resources required by the deer and forage resources available are out of balance. A large number of deer should be reMoved from the Crane Memorial Reservation and Wildlife Refuge if both natural and Man-made habitats are to be restored there.
Methods of population reduction on the Reservation and the Refuge need to be given careful consideration with regard to their feasibility and appropriateness for these areas. Evaluations of trapping and regulated hunting follow.
Trapping
Trapping deer is not as siMple as setting up a trap, checking it each day, and caring for or disposing of an aniMal. On the contrary, trap design is an iMportant consideration in terMS of cost, safety, and success. Cost is a predictable consideration that can be evaluated. Safety considerations Must be preventive, both in relation to the aniMal and personnel handling traps and aniMals. Deer which appear to be taMe revert to their wild instincts when
78
they are cornered; ExtreMe precautions years of rearing and
deer are particularly swift to strike with their hooves. were iMpleMented and enforced by the author in ~everal
handling deer at Cornell's Wildlife Ecology Laboratory.
Trapping success is extreMely variable, depending on tiMe of year, aniMal condition, and aniMal experience with traps. A group of deer observing another deer trying to escape froM a trap will be More wary and less vulnerable to trapping after such an experience. Thus trapping techniques pose probleMs, and trapping will likely not be successful enough to reMove the nUMbers of deer necessary to restore a balance between deer nUMbers and habitat resources. Should trapping be given consideration as part of a reduction and control prograM, two Methods of disposal are discussed next.
Trap and transfer. Trap and transfer of deer frOM the Crane areas to other areas cannot be considered a reasonable option because (1) habitats suitable for deer are already occupied, (2) it is not desirable because of stress on the aniMals when trapped, transported, and released into new habitat already occupied by deer, (3) the threat of spreading LYMe disease is a risk that cannot be taken, and (4) trap and transfer will not solve the deer population probleM as deer reMaining on the Crane areas will continue to reproduce, probleMS associated with an overpopulation will continue, and trapping will beCOMe less successful with tiMe.
Trap and euthanize. Trapped aniMals should be destroyed as hUManely as possible. "Euthanasia is the act of inducing painless deat.h " for t.he aniMal being subjected to euthanasia" (McDonald et al. 1978). A nUMber of factors, including the species and nUMbers of aniMals involved, available Means of control of the aniMal, condition of the aniMal, skill of personnel, and econoMic factors should be considered when choosing a Method of euthanasia. Eleven criteria for judging Methods of euthanasia are given in McDonald's report; no single Method is Most desirable. Further, wild species are different frOM dOMestic species; deer pose special probleMS, and are Much More difficult to restrain and euthanize than even large dOMestic aniMals such as cattle and horses. Selection of Methods for euthanizing deer under different cirCUMstances, if this is an option selected by The Trustees of Reservations, should be Made in consultation with veterinarians, and personnel involved will need to have the necessary training in procedures. Provisions Must also be Made for disposing of the carcass, depending on the Methods used for euthanizing and whether or not the Meat is considered a usable resource.
Regulated hunting
Regulated hunting is a cost-effective Method of controlling deer populations because aniMals are reMoved without directly handling theM and with no need for extensive equipMent and personnel. The Crane MeMorial Reservation, with its buildings and grounds, would require carefully-planned and regulated hunts, with other public uses of the area strictly controlled during any kind of hunting. Two Main kinds of regulated hunting should be considered, including quota hunting and season hunting.
Quota hunhng. Quota hunting continues unt.il a specified nU~lber~ of aniMals have been reMoved. The nUMber of deer that should be reMoved frOM the Crane areas to Meet population goals has been deterMined, and quota hunting could be conducted with a daMage perMit issued by the Massachusetts Division of Fisheries and Wildlife.
79
Season hunting. Hunting is legally perMitted during specified seasons. Hunting during the regular deer season could be conducted on the Crane areas if the hunters were carefully screened to deterMine their qualifications, and the nUMber of hunters strictly regulated. The selection of hunting as an option should be considered in relation to both reducing the extra-high population of deer on the Crane areas and controlling the population after the nUMber of deer has been reduced to a level within the carrying capaCity of the habitat. Deer hunting was an annual activity on Hog Island with the perMission of Mr. Crane, according to Walter Prisby, the present refuge Manager, who was eMployed by the Crane faMily prior to the Trustees aSSUMing ownership of these properties.
Deer are deer then
Population control
populations, once reduced, will increase again unless control Measures taken. It is Much easier to Maintain control over annual increMents of populations than it is to allow theM to build up for several years and try to reduce theM to Much lower levels. SOMe Methods of population
control are discussed next.
Controllina nUMbers
The nUMber of deer on the Crane properties will stabilize when natality rates and Mortality rates are equal. This will occur at SOMe high nUMber of deer such as are present now, in which case 75 or More deer Must die each year, priMarily frOM starvation. The Moral issue of allowing such a high die-off deserves careful consideration. Many deer are born without a chance to live; large nUMbers of fawns are dOOMed to die before they reach the age of one year. A controlled population, within the carrying capacity of its habitat, will have Many fewer deer present, and even though the reproductive rate of the feMales will be higher (this was conSidered in the reMoval evaluations discussed on pages 48-51), Many fewer deer need be reMoved each year to keep the population under control than will die of starvation when the population is too high. In fact, an ecologically appropriate population on the Crane areas would be SMaller than the nUMber of deer which Must die each year under current conditions. If the population were 50 deer, less than 30 Mortalities, SOMe of theM due to environMental effects, would be needed each year for the population to reMain stable. Brief discussions of control over Mo~tality and natality follow.
Controlling Mortality. Control over Mo~tality is possible only with SOMe Method for reMoving deer. Hunting is a Widely-used Method of population control which results in the Maintenance of an appropriate balance between aniMal requireMents and resources available; In general, there is a conservative attitude toward hunting, fishing, logging, and reMoval of other natural Material frOM natural areas, and the public which supports nature preserves is against hunting in theM. Hunting of wild aniMals on areas which May be broadly defined as nature preserves and natural areas varied aMong 11 states surveyed by Bowles (1981). Over 40% of the states allow hunting on preserves, often in recognition of the biological necessity of reMoving SOMe aniMals in order to preserve a significant natural area, usually on a case-bycase basis. Such areas are not Managed for the production of gaMe aniMals, however. A proposal for a COMprehensive ecology and ManageMent prograM for the Crane MeMorial Reservation and Wildlife Refuge is given on page 83.
80
Controlling natality. Natality cannot be controlled in free-ranging species. If individuals are captured, reproductive inhibitors May be used to reduce the population's reproductive rate by rendering SOMe of the individuals sterile, at least for a tiMe. The use of reproductive inhibitors is particularly appealing in zoos where a specified nUMber of individuals is perMitted and additions are not welcoMed. The use of reproductive inhibitors has really just begun, and Seal et al. (1976) list Many considerations to be Made when iMpleMenting plans for the use of reproductive inhibitors. An experiMental prograM to help control nUMbers of deer on the Crane areas by uSj,ng reproductive inhibitors could be conSidered, although it Must be recognized that the Crane areas are near and adjacent to private and public lands on which deer populations May be Managed differently. This raises SOMe legal questions, and it MUSt also be pointed out that reproductive inhibitors are not yet registered with the U.S. EnvironMental Protection Agency for controlling big gaMe populations (Matschke et al. 1984). Further, the success of reproductive inhibitors is Much More doubtful on open areas such as the Reservation and Refuge than on closed areas such as the one-square-Mile Angel Island off the coast of California. There, individual feMale black-tailed deer have been captured and iMplanted with a reproductive inhibitor as part of a prograM to prevent population increases (AnonoMYs 1984). The potential for such a prograM was discussed by Harder and Peterle (1974) who pointed out that intraMuscular adMinistration of a reproductive inhibitor (diethylstilbestrol in their experiMents) was very effective on the individual but would be useful only on SMall populations. Any experiMental use of reproductive inhibitors on the Crane areas should be accoMpanied by cOMputer-based population siMulations which evaluate the overall effectiveness of the inhibitors, not only in relation to the individual feMale's response but also to population dynaMics.
Controlling behavior
Wild aniMals do not necessarily abide by the wishes of the land "owner" upon which they reside. Low populations May still contain individual aniMals who choose to den, eat, or otherwise use resources in an area not suited for their presence. Thus SOMe Measure of control over the behavior and activities of aniMals May be needed to Make SOMe Man-Made features. OrnaMental plantings, for exaMple, May need to be protected by fences, especially during the first years after establishMent. Flower gardens should be placed where aniMal activity is less likely to occur. A garden next to a few acres of woods is Much More vulnerable to wildlife iMpacts than a garden in the Middle of a large Mowed lawn. Such considerations should be part of the long-range planning for restoration of the Crane MeMorial Reservation.
Wildlife Manage~ent on Natural Areas
Wildlife ManageMent on natural areas and preserves poses several probleMS, siMply because such areas are used for Many different purposes. SOMe natural areas are closed to the public in order to protect fragile habitats. On SOMe, public use is encouraged. On MOSt, uses are non-consuMptive; collections of any kind are not perMitted, except perhaps for scientific purposes. Thus the iMpression is given that such areas are "natural" or will beCOMe natural if given enough tiMe. Such iMpressions are not ecologically correct; direct or indirect influences by Man prevail over just about every bit of land in the U.S. Lands set aside as natural areas will revert to More natural conditions than if they were farMed, Managed as COMMercial forests, or "developed" for
81
SOMe particular hUMan use, however, and it is iMportant to understand the potential of each area for such reversions, and the long-terM values of such areas in understanding ecological relationships.
Wildlife ManageMent on natural areas is used as a title for this sect jon of this report, but it is not Meant to iMply that establishMent of a "wildlife ManageMent" prograM should be the goal of The Trustees of Reservations. Rather, an "ecology and ManageMent" prograM, with considerations given to both plants and aniMals, is a More appropriate perspective. Such a perspective will reveal, based on careful ecological analyses, that restoration of habitats to More natural conditions can only be aCCOMplished with the control of SOMe species of plants and aniMals. Prairies, for exaMple, are invaded by shrubs and trees and becoMe woodland if given protection froM fire. Allowing fire to burn on such areas May appear to be bad but it is ecologically good. A siMilar conceptual approach to the control of a variety of plants and aniMals is needed when evaluating successional trends on natural areas.
ManageMent, however, is an act or an activity rather than a goal.
Let us never pretend that ManageMent is the greater portion of the solution to environMental probleMS. Understanding is the greater portion, and only after that has been achieved can we proceed with wise ManageMent of but a sMall portion of the natural world.
How should we proceed to increase our understanding of ecological relationships on the Crane MeMorial Reservation and Refuge? First, inforMation about the natural characteristics of these areas should be cOMpiled. COMpiling inforMation is not enough, however. It Must be COMpiled in a forMat that is useful, that will enable people to access it, evaluate it, and recognize ecological relationships between these natural characteristics. The only reasonable way to do that in this decade is with electronic inforMation processing; COMputers provide us with iMpressive energetic and Mental leverages (Moen 1983c).
Electronic inforMation processing Makes it possible to use a data base ManageMent approach, not only to catalog inforMation but also to evaluate relationships. Such a data base ManageMent prograM should be set up for both the Reservation and the Refuge, and should include data on and evaluations of both plant and aniMal characteristics. Such a cOMputer-based data ManageMent prograM would provide ready access to the status of the plant and aniMal species present. Data on wildlife species should include such things as sightings of Wildlife, nest records, observations, life history inforMation, population estiMates, population SiMulations, control Measures taken, etc.
The use of such a cOMputer-based systeM on the Crane areas could beCOMe a Model, a prototype for other natural areas and nature preserves. Further, funding for such a systeM would likely be available frOM both public and private sources, because grants to The Trustees of Reservations for this purpose would have far-reaching iMplications for the welfare of all species on such areas.
82
IMMediate action could be taken, at relatively little cost, to evaluate and deMonstrate the iMpact of deer on the habitat characteristics on the Crane areas. SMall exclosures should be put up to protect growing plants frOM deer foraging, allo~ing plants present to recover and a More natural plant species diversity restored. The plant species residual in the understory which would appear in these exclosures are not known, but evaluations could begin as early as 1985 and recovery and restoration plans Made.
Technical help is becoMing ~vailable for recovery and restoration of natural areas after they have been exposed to overuse. The Natural Areas Journal, published Quarterly since 1981 by The Natural Areas Association, provides inforMation on research and ManageMent activities for nature preserves, natural areas, parks, rare species ManageMent, land preservation techniques, and theoretical approaches to natural areas work. The Natural Areas Association is a national, non-profit organization of individuals actively involved in the identification, preservation, protection and ManageMent of natural areas and eleMents of natural diversity.
Another technical publication, Restoration & ManageMent Notes, also appeared in 1981, and is a forUM for the exchange of news, views, and inforMation aMong ecologists, land reclaMationists, Managers of parks, preserves and rights-of-way, naturalists,. engineers, landscape architects and others COMMitted to the restoration and wise stewardship of plant and aniMal COMMunities. The recent appearance of these two technical publications is indicative of the current interest in restoring the health of the land in general and of set-aside areas in particular.
A Long-range EcosysteM Recovery and Restoration PrograM
An aniMal control specialist has been suggested as a position with responsibilities for planning and Managing deer reduction and control prograMS in the iMMediate future. The urgency of deer herd reductions is obvious after exaMining the iMpact of deer on the habitat at the Crane MeMorial Reservation and Wildlife Refuge. The different· Methods that could be used need careful consideration in relation to safety, cost, and other factors. This is only a first step, however.
Planning should begin iMMediately for the establishMent of a habitat restoration and recovery prograM. This prograM should include the responsibilities to be aSSUMed iMMediately by the aniMal control specialist, and an overall prograM of restoration and recovery of the habitat begun. Read the discussion of "wildlife ManageMent on natural areas" on pages 81-83 again, and consider the potential of the Crane areas for restoration. Diversity of both plants and aniMals can be restored to the Crane areas. The need to establish long-range plans is siMply good ManageMent, which can surely be conducted in a rational way as understanding of ecological relationships is gained.
83
84
SUMMARY
Metabolic energy requireMents and the aMount of forage necessary to Meet these requireMents have been calculated for white-tailed deer populations on the Crane MeMorial Reservation and Crane Wildlife Refuge. The nUMber of deer on these areas during the winter greatly exceeds the nUMber that should be supported by the available forage resources.
Deer dOMinate the understory vegetation on the Crane areas. Woody plants are heaVily browsed, and the herbaceous species present are influenced greatly by deer. TrilliuM, a COMMon spring flower, for exaMple, is expected to be present in upland hardwood stands, but none were found on the Reservation in the spring of 1984.
Target populations of 36 deer on the Reservation and 15 deer on the Refuge have been deterMined froM carrying capacity analyses. Since freeranging deer cannot be controlled as precisely as dOMestic aniMals in pastures and barns, 30-to-40 deer and 1Z-to-18 deer are reasonable population goals for the Reservation and Refuge, respectively.
Reductions in the nUMber of deer present on the Crane areas should follow a carefully-planned schedule over a 3-to-5 year period, with frOM 30% to 45% of the deer reMoved each year.
Reductions in the nUMber of deer should be followed by control of deer nUMbers in order to prevent a reoccurrence of over-population. COMputer-based population evaluations indicate that an average of about 6-8 deer would need to be reMoved frOM the Reservation and 3-5 deer frOM the Refuge each year to stablize the population. The nUMbers that need to be reMoved can be altered by selecting according to sex and deer condition; selectively reMoving smaller and weaker aniMals would be quite appropriate.
If the population is not reduced, it will level off as a result of starvation and other related deCiMating factors. The nUMber of deer expected to die each year as a result of poor habitat conditions is greater than the nUMber of deer that should be present on these areas.
EstablishMent of an aniMal control specialist pOSition to oversee the population reductions that should begin as soon as possible is reCOMMended. It will not be easy to reduce the populations on the Crane areas to the levels necessary to restore and recover plant COMMunities; intensive and well-planned reduction procedures will need to be carried out over a 5-year period under the direction of the aniMal control specialist.
ExperiMental work on the use of reproductive inhibitors could be considered, but since deer Move to and frOM the Crane areas, several biological and legal questions Must be addressed.
A potentially significant deer-hUMan interaction that has appeared recently is that of LYMe disease. Since deer are part of the life cycle of the tick which tranSMits this disease, deer populations have the potential for affecting the incidence of LYMe disease in hUMans.
85
The Crane areas are not only very sMall in cOMparison to areas used by deer, but they are also surrounded by hundreds of parcels of private land and a nUMber of residences. Thus ecological relationships on the Crane areas are quite unlike those in large parks and preserves where wild aniMals have a high if not the highest priority.
CirCuMstances have developed on the Crane areas which call for creative solutions to probleMs associated with wildlife-huMan interactions, solutions which will result in a diverse array of both plants and aniMals. Having appropriate levels of wildlife populations--neither too Many nor too few aniMals--can be expected to MiniMize local probleMs while providing an array of species to be enjoyed.
86
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