Rich OlsonDepartment of Renewable Resources

B-965February 1992

Mule Deer

Habitat

Requirements

&Management

in Wyoming

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Mule Deer Habitat Requirements andManagement in Wyoming

ByProfessor Rich Olson

Department of Renewable ResourcesCollege of AgricultureUniversity of Wyoming

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IntroductionMule deer (Odocoileus hemionus) in Wyoming provide recre-ational, aesthetic, and economic values to hunters, wildlifeenthusiasts, and local business throughout the state. Morethan 100,000 hunters annually pursue this species in Wyo-ming, spending an average of more than 336,000 days in thefield to harvest more than 60,000 animals. Local businessessuch as motels, grocery stores, gas stations, and sportinggoods stores receive considerable revenue each year as dolandowners who charge access fees for mule deer hunting.

Habitat RequirementsMule deer are mostly ac-tive during late after-noon, early evening, andearly morning hours.The rest of their day isspent resting in heavysagebrush draws, rockyoutcrops, or juniper/as-pen thickets. Hiding orresting locations are se-lected to provide con-cealment, a view of thesurrounding terrain, andeasy access to escaperoutes. Steep and ruggedtopography that providesbrush-like vegetation ispreferred habitat.

Mule deer are highly mobile for short periods such as the falland spring during migration between winter and summerranges. However, for most of the year they establish “home

Figure 1 – Steep and rugged topography thatprovides heavy sagebrush draws, rocky outcrops, aview of surrounding terrain, and easy access toescape routes comprises ideal mule deer habitat inWyoming.

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ranges,” which mayvary from a few hun-dred acres to more thana square mile depend-ing on the arrangementand abundance of es-sential food, cover, andwater. Deer densitiesdepend on adequateand well-distributedfood, cover, and water.

In Wyoming, mule deerranges may support apopulation all year(year-long range) oronly during a portionof the year (seasonalranges such as winter,summer, or transitional

spring-fall). The ideal combination of essential habitat com-ponents (food, cover, and water) to support maximum deerdensities will vary with the type of range. For example, es-cape cover may not be as important on winter range as infawning areas, water is more important on late summer andfall ranges than on winter range, and certain evergreenshrubs are more important as cover on winter range than onsummer and transitional ranges. On year-long range, allthree essential habitat components must be present to sup-port deer populations.

Water RequirementsMule deer obtain much of their required water from foodssuch as vegetation growing near water. When native vegeta-tion and temporary ponds dry up in late summer and early

Figure 2 – Draining permanent water sources anddewatering springs degrades mule deer habitat byeliminating watering areas and essential food andcover growing on these moist sites.

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fall, deer depend on permanent streams, springs, and seepsfor daily water intake. The best way to ensure adequate wateron deer range is to avoid the destruction of habitat aroundpermanent water sources. Dewatering of springs and seepsnot only eliminates a source of water in late summer and fall,but it also removes essential food and cover growing in thesemoist areas.

Cover RequirementsMule deer cover requirements fall into two major categories:hiding cover (also know as escape or security cover) andthermal cover. Unlike antelope, deer do not have the abilityto escape predators through extended, high-speed maneu-vers. Typically, mule deer rely on bursts of energy to seek se-curity in rough terrain with dense vegetation for protection.Feeding deer rarely venture far from a draw of tall sagebrush,a pile of rocks, or a thicket of large shrubs or trees.

Hiding cover, defined as “any vegetation capable of hiding90 percent of deer from human view at a distance equal to orless than 200 feet,” is needed throughout the year. Scatteredpatches of relatively dense vegetation from 10-30 acres insize are adequate for hiding if the patches are not more than0.25-0.5 miles apart. Rough and rocky terrain complementsvegetation used as hiding cover. Varied topography alonedoes not provide suitable hiding cover.

Thermal cover is necessary to protect deer from cold tem-peratures, high winds, and winter snows as well as from heatand insects in summer. For example, dense juniper stands inwinter decrease body-heat loss in mule deer by providingprotection from bitter cold winds and reducing heat loss dueto exposure and radiation. This protection allows mule deerto conserve energy for body maintenance and reproduction.

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Small evergreentrees and shrubson winter rangesand deciduoustrees and shrubson summer andtransitionalranges provideexcellent ther-mal cover fordeer. For ex-ample, decidu-ous trees such ascottonwood oraspen provide

overhead shade and open under stories to allow passage ofcool breezes during summer. Ideal summer thermal coverconsists of sapling trees or shrubs at least 5 feet tall with 75percent closure of the canopy.

Winter thermal cover in a forest vegetation type should in-clude evergreen trees of pole size or larger with at least 60percent closure of the crown. Optimum patches of winter orsummer thermal cover should be 2-5 acres in size and com-prised of vegetation at least 3-5 feet tall. Juniper communi-ties are important to mule deer for summer and winter ther-mal cover as well as for providing cover for daily movementpatterns.

Topographical features such as scattered boulders, gullies,and draws and leeward sides of ridges and rim rocks enhancethe cover value of plant communities commonly used bydeer. During summer, deer often lay in shaded spots on rimrocks overlooking the surrounding terrain.

Figure 3 – Coniferous trees and shrubs on winter range providenecessary thermal cover by protecting mule deer from cold tempera-tures, high winds, and winter snows.

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FoodRequirementsBecause muledeer food variesseasonally, im-portant muledeer range re-quires a mixtureof trees, shrubs,(woody, peren-nial plants oflow heights),forbs (herba-ceous, broad-leaved floweringplants), and grasses. Locations where food, cover, and wateroccur together are preferred feeding areas. For example, op-timum mule deer winter range is comprised of approximately45 percent scrubland and 45 percent coniferous forest, withthe remaining 10 percent in forbs/grassland. Mule deer gen-erally will not use feeding areas farther than 0.5-1 mile fromsuitable hiding and escape cover.

Mule deer select foods that are palatable, succulent, and nu-tritious. However, seasonal availability of various plants andseasonal metabolic requirements of deer also influence theselection of food materials. Generally, the seasonal food hab-its of mule deer include the following:

Spring – As early greening grasses and forbs emerge, muledeer stop eating shrubs of relatively low nutritional value andstart consuming palatable, succulent, and nutritionally richherbaceous plants. In late spring, their diet includes a varietyof grasses and forbs with a few shrubs.

Figure 4 – Optimum mule deer winter range is comprised ofapproximately 45 percent shrublands, 45 percent coniferous forest, and10 percent forbs/grassland.

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Summer – During thisperiod, mule deer use awide variety of habitatsand consume many dif-ferent foods. However,as grasses dry and cure,consumption decreasesto a very low level. Atthis time, forbs some-times comprise as muchas two-thirds of the diet.In late summer, deer be-gin to replace forbs intheir diet with shrubs.

Fall – With fall frosts,mule deer shift to pre-dominately shrubbyvegetation. Forbs still

receive moderate use if available and may account for up to25 percent of the diet.

Winter – During this period, trees and shrubs comprise 75percent or more of the deer diet because other kinds of foodare dead and usually covered by snow.

Plants comprising mule deer diets in the summer and winterare listed in Table 1. However, studies conducted in Wyo-ming indicate that the following plants are especially impor-tant to mule deer in winter: sagebrush (Artemisia spp.), ante-lope bitterbrush (Prushia tridentata), mountain mahogany(Cercocarpus spp.), and rabbit brush (Chryosthanmus spp.).

Important summer plants include willow (Salix spp.), huckle-berries (Vaccinium spp.), shrubby cinquefoil (Potentillafruitcosa), buffalo berry (Shepherdia Canadensis), and a vari-ety of forbs previously mentioned.

Figure 5 – Curlleaf mountain mahogany isconsidered an “ice cream” food plant for mule deerdiets.

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Table 1. This is a partial list of plant species and their relative value asfood and cover for mule deer in Wyoming.

Hiding/Summer Winter Escape Thermal FawningForage Forage Cover Cover Cover

TreesPonderosa Pine Poor Poor Good Excellent FairRocky Mountain Juniper Poor Fair ExcellentExcellent GoodCottonwood Fair Fair Fair Good Poor

BrowseTrue Mountain Mahogany ExcellentExcellent ExcellentGood ExcellentCurlleaf Mountain Mahogany ExcellentExcellent ExcellentGood ExcellentAntelope Bitterbrush ExcellentExcellentGood Good GoodBig Sagebrush Fair Good Good Good ExcellentBlack Sagebrush Fair Fair Poor Poor PoorRubber Rabbitbrush Good Good Poor Poor PoorServiceberry Good Excellent Good Fair GoodCurrant Good Good Poor Poor FairWillow Good Excellent Good Good ExcellentShrubby Cinquefoil Good Good Good Fair FairBuffaloberry Good Good Good Fair Fair

ForbsRed Clover Good Poor Poor Poor PoorYellow Sweet Clover Good Poor Good Fair GoodDandelion Fair Poor Poor Poor PoorBuckwheat Good Poor Poor Poor PoorFireweed Good Poor Poor Poor PoorHuckleberry Good Poor Poor Poor PoorVetch Good Poor Poor Poor Poor

Grasses and GrasslikeIdaho fescue Good Poor Poor Poor PoorBluebunch Wheatgrass Good Poor Poor Poor PoorCarex Fair Poor Poor Poor Poor

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In some areas ofWyoming, muledeer diets may in-clude a variety ofagricultural crops.This is particularlytrue where farm-lands are adjacentto wintering areasor in areas of lim-ited precipitationwhere crops arethe only food

sources available. However, mule deer rarely subsist entirelyon agricultural crops.

Other Habitat RequirementsFawning habitat – For fawning, mule deer select 1 to 5-acreareas with adequate water, cover, and succulent vegetation.Succulent plants and free-standing water are essential fordoes to produce milk for nursing. Ideal fawning habitat in-cludes areas of low shrubs or small trees 2-6 feet tall, anoverstory tree cover of approximately 50 percent, slopes lessthan 15 percent, and water within 600 feet. Lush, succulentvegetation should be available, especially in June during thepeak of fawning. Riparian habitats offer quality fawning con-ditions for improved growth rates and survival during thefirst year of life.

Special Seasonal Habitat Needs – Adequate winter range ingood condition is essential for mule deer populations. Dur-ing winter, mule deer prefer open-timbered, west-facing ex-posures and shrub-covered, south-facing exposures wherewarmer temperatures exist, snow pack is minimal, preferred

Figure 6 – Sagebrush is especially important in the winter diet of muledeer.

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Table 2. This is a summary of optimum habitat combinations for muledeer on summer/transitional range and winter range.

Escape/Foraging Hiding Thermal FawningAreas* Cover Cover Cover

Summer/Transitional Range 60 22 11 7

Winter Range 60 15 25 0

Percent of habitat type

browse (twigs or shoots of woody plants) is abundant andavailable, and food and cover are close together.

Interspersed Habitat – Studies indicate that the optimumcombination of cover types required by deer on summer andtransitional ranges includes: (1) 20 percent hiding cover, (2)10 percent thermal cover, (3) 5 percent fawning cover, and(4) an additional 5 percent of combined hiding, thermal, orfawning cover, (Table 2). The remaining 60 percent of themule deer range should be feeding areas. On winter range,there should still be 40 percent cover and 60 percent feedingareas with an increased percentage of thermal cover.

Habitat Improvement Techniques

Water Development and Management

Strategically placed water developments influence mule deerdistribution, particularly during hotter periods of the yearwhen deer need more water. Contact the Wyoming Gameand Fish Department, Bureau of Land Management, U. S.Forest Service, or Soil Conservation Service in the area forassistance in designing and/or constructing watering devices

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for mule deer. Fol-lowing are generaldevelopment andmanagementspecifications:

• Maintain a dis-tance of 2.5 to 3miles between wa-ter developmentsand locate waterdevelopmentswithin 0.5 to 1mile of mule deercover and feedingareas.

• Where feasible, develop a number of small wateringponds rather than one or two large lakes. Ensure thatponds have a source of fresh water to avoid water-qualityproblems.

• Strip-mining operations often make water available fromunderground springs and water tables. These additionalwater developments will help protect riparian areas thatprovide valuable mule deer habitat.

• Maintain water in cattle troughs and spring-fed pondseven if livestock are not using them and ensure thattroughs are low enough for fawns to use.

• If mule deer are not using a water source, have Univer-sity of Wyoming scientists or the state hydrologist ana-lyze a water sample for mineral content. Mule deer willnot use water containing high salt concentrations. Waterwith a total soluble salt content of less than 1,000 partsper million is best for mule deer use.

Figure 7 – Water developments such as livestock troughs areimportant for mule deer, particularly during the summer and early fallwhen water consumption demands are greater. Watering troughsshould be low enough for fawns.

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• Avoid concentrating cattle in riparian habitat or nearother sources of water where degradation of riparian veg-etation and water quality may occur. Judicious livestockgrazing management or fencing may be needed to avoidhabitat degradation for mule deer.

Tree and Brush Management

Coniferous forests and juniper stands provide excellent hid-ing and winter thermal cover while deciduous trees such asaspen and cottonwood provide thermal cover on summerand transitional ranges. Extensive clear-cutting in coniferousforests where thermal cover patches are reduced to less than10-acre blocks should be avoided. Likewise, extensive brushcontrol in juniper stand should be avoided to preserve theintegrity of the stand for winter cover, summer cover, anddaily travel routes for mule deer. Following are specific treeand brush management ideas:

• Selective thinning of decadent juniper can be accom-plished by bulldozing or cutting individual trees as longas a canopy cover of at least 40 percent is maintained.

• Chain or bulldoze small, widely scattered clearings toopen up extremely dense juniper stands. This can bebeneficial to mule deer if the resulting efforts do notleave islands of juniper among large patches of clearedbrush. Clearing should be long and irregular in shape,less than 20 acres in size, less than 200 feet in width, atleast 0.5 miles apart, and screened from roads by at least600 feet of brushy vegetation.

• Stimulate sprouting and regrowth in decadent aspenpatches from summer thermal cover by clear-cutting orburning selected stands over a prescribed interval of 10to 20 years.

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• If water manipulation is possible on cottonwood-domi-nated areas, periodic flooding over a prescribed intervalin selected locations will enhance summer thermal coverwithin this community type.

• Extensive brush control on key winter ranges dominatedby shrubs important in the winter diet of mule deershould be avoided. However, prescribed burning and/ormechanical treatments such as rotobeating can be imple-mented on small, selected patches within the winterrange every few years to maintain browse condition andproduction. Rotobeating to stimulate shrub productionis most successful in areas receiving at least 12 inches ofprecipitation annually.

Prescribed Burning

Prescribed burning encourages grass and forb production onsummer and transitional ranges, removes rank dead grassresidue, and stimulates sprouting of browse plants such astrue mountain mahogany, chokecherry, serviceberry, rabbitbrush, snowberry, and aspen on winter range. However,burning can temporarily eliminate browse plants such assagebrush, antelope bitterbrush, and curl leaf mountain ma-hogany, especially if the burn gets too hot. Follow theseguidelines for burning:

• Prescribed burning should follow detailed prescriptionsfor the intended management goals and should be con-ducted only in years with average or above-average pre-cipitation. Adequate soil moisture is essential for vegeta-tive growth following burning.

• Late summer and early fall burns in 50 to 100-acrepatches are ideal for grass and forb enhancement whilespring burns are preferred to enhance shrubs that re-spond by sprouting.

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• Where live-stock grazingis present,burn onlywhere live-stock can beexcluded for atleast twogrowing sea-sons followingthe burn toallow for plantreestablish-ment.

• Do not re-burn grass/forb areas for at least 5 to 7 years and shrub areas for atleast 10 to12 years. This interval can vary depending onthe site-specific moisture regimes, soil conditions, andclimatic factors.

• Contact the Wyoming Game and Fish Department, Bu-reau of Land Management, U. S. Forest Service, and/orSoil Conservation Service for assistance and planningprior to burning.

Browse Establishment

Browse can be enhanced on winter ranges by drilling orbroadcast seeding of mountain mahogany, antelope bitter-brush, winter fat, and four-wing saltbush, provided moistureand soil conditions are suitable for germinations. Followingare specific recommendations:

• Do not seed browse plants where livestock may disturbnewly seeded areas or utilize emerging growth. Seedings

Figure 8 – Prescribed burning can benefit mule deer by stimulatinggrass and forb production on summer and transitional ranges,removing rank dead grass residue, and encouraging the sprouting oftrue mountain mahogany, chokecherry, serviceberry, rabbitbrush,snowberry, and aspen on winter ranges.

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should be deferred from livestock grazing for at least twogrowing seasons to allow establishment of seeded shrubs.

• While planting depth varies, a general rule is to plant 2.5times deeper than a seed is wide (about 0.25-.05 inches).The seeding rate is roughly 1 to 3 pounds per acre formost browse plants.

• Newly seeded areas should be covered with soil or mulchto preserve moisture.

• Scraping, spraying, or disking may be required to reducecompetition from established plants prior to seeding.

• Consult seed companies and the Soil Conservation Ser-vice for assistance in recommended seeding rates, depth,soil adaptations, and species selection prior to seeding.

Planting and Propagating Food Patches

Where climatic conditions are favorable, the establishmentand propagation of cereal grains (wheat, barley, or oats)and/or legume food patches (alfalfa, yellow sweet clover, redclover, or vetches) may enhance mule deer nutrition. Strate-gically located food patches adjacent to cover are essential fordeer use. The following recommendations are for foodpatches designed for mule deer.

• Food patches should be located within 0.5 mile of muledeer cover or access routes like canyon rims or ravines.

• To provide adequate supplemental forage there shouldbe 0.5 acre of wheat, barley, or oats per deer.

• Several strategically located 20-acre fields are more desir-able than one 100-acre field to avoid concentrations andensure access by more deer.

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Figure 9 – Spring and early summer grazing by livestock can enhancewinter browse for mule deer by providing a competitive growingadvantage for some shrubs when herbaceous plants are grazed at thistime of the year.

• For spring,summer, andfall foraging,legumeplantings arepreferable. Ce-real grains arebetter for falland winter for-aging wherethere is nottoo muchsnow accumu-lation.

• Avoid deerhunting on ornear food patches to avoid discouraging deer use of thepatches.

• Postpone livestock grazing on cereal grains until afterdeer have moved onto newly emerged spring vegetationand on legumes until after deer have started browsingshrubs.

Livestock Grazing Management

Although cattle and mule deer generally do not compete forthe same forage, livestock grazing can be managed to en-hance rangeland vegetation for mule deer. Following are spe-cific recommendations for livestock grazing to enhance muledeer forage:

• To enhance winter browse for mule deer, studies indicatethat spring and early summer grazing of herbaceousplants by livestock that prefer grasses and forbs provides a

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competitive advantage to shrubs competing with herba-ceous plants for soil water, nutrients, and minerals. Alter-natively, to enhance herbaceous plants for spring andearly summer use by mule deer on transitional and sum-mer ranges, sheep grazing in late summer and early fallwill provide a competitive advantage to grasses and forbsover shrubs such as sagebrush.

• Moderate to light stocking of cattle will stimulate range-land vegetation and improve overall range condition.Consider reducing stocking rates in areas adjacent tomule deer cover, particularly riparian habitat.

• Rotational and/or deferred grazing systems will enhancerangeland vegetation, especially herbaceous plants, usedby mule deer in spring and early summer.

• Avoid concentrating cattle in juniper stands, especiallyduring the winter when mule deer are concentrated inthe same areas.

With just a little knowledge about mule deer habitat require-ments, landowners and wildlife enthusiasts alike can adoptmanagement practices to benefit mule deer that are compat-ible with other uses. For more information on mule deerhabitat management, contact a University of Wyoming Co-operative Extension Service educator or visit a local Wyo-ming Game and Fish Department district office.

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AcknowledgementsInformation presented in this bulletin was extracted primarilyfrom the following references:

Wyoming Game and Fish Department. 1976. Considerationsfor Wildlife in Industrial Development and Reclamation.Cheyenne: Wyoming Game and Fish Department.

Wyoming Game and Fish Department. 1978. The Mule Deerof Wyoming. Bulletin No. 15, Cheyenne: WyomingGame and Fish Department.

References for Further ReadingBryant, F. C. and B. Morrison. 1985. Managing Plains Mule

Deer in Texas and Eastern New Mexico. ManagementNote No. T-9-414. Lubbock: Texas Tech University,Range and Wildlife Management Department.

Strickland, D. 1975. Mule Deer in the Medicine Bow Moun-tains, Southeastern Wyoming. Wildlife Technical ReportNo. 2. Cheyenne: Wyoming Game and Fish Depart-ment.

Soil Conservation Service. 1986. Mule Deer. Technical NoteNo. 110. Casper: Wyoming State Office, U. S. Depart-ment of Agriculture.