H.T. Davies-Mostert, M.G.L. Mills & D.W Macdonald

Hard boundaries influence carnivore diet and prey

selection

INTRODUCTIONPATTERNS OF PREY SELECTION Energetic benefits and costs

(Griffiths 1975, Creel & Creel 2002)

Mechanisms of selection

Search images

Prey vulnerability

Habitat characteristics relating to hunting or escape (Kruuk 1972, Husseman et al. 2003)

INTRODUCTIONHUMAN MEDIATED CHANGESPotential to disturb

evolutionarily stable predator-prey relationships Water provisioning in KNP:

lions and rare antelope (Harrington et al. 1999)

Extensive habitat alteration due to agricultural practises (Sweitzer et al. 1997)

Reduction of suitable habitat into smaller patches (mesopredator release - Crooks & Soulé 1999)

INTRODUCTIONTHE SOUTH AFRICAN CONTEXT Predator-proof fencing limits

movements of predators and prey

Spate of reintroductions (Marnewick et al. 2007, Funston 2009, Davies-Mostert et al. 2009)

High perimeter-to-area ratios increase likelihood of contact with fences

Suggested that carnivores modify their hunting behaviour (van Dyk & Slotow 2003; Rhodes & Rhodes 2004)

different species, size classes, sex and condition, overall hunting success, etc

Implications for the sustainability of reserves to support carnivores

Large carnivore ~25kg Endangered (Globally, Nationally) Social, pack-living

Cooperative rearing of young Hunting

Coursing predator Kills likely when prey become

exhausted, mean chase 0.57 km, 0.05 m-4.60 km (Creel & Creel 1995)

Likely to exert higher selection for animals in poor condition than ambush predators, southern Zimbabwe (“survival of the fittest” - Pole et al. 2004)

High energy requirements (Gorman et al. 1998)

15MJ/day for 3.5 hour day Working border collie – 8.2MJ in 6

hours

INTRODUCTIONAFRICAN WILD DOG Lycaon pictus

Pole et al. 2004

WILD DOG METAPOPULATION

1. Hluhluwe-iMfolozi Park

2. Madikwe Game Reserve

3. Pilanesberg National Park

4. Venetia Limpopo Nature Reserve

5. Marakele National Park

6. Tswalu Kalahari Reserve

7. Mkhuze Game Reserve

8. Balule Game Reserve

9. Thanda Private ReserveDavies-Mostert, 2010

Note:- Most sites not much bigger than AWD home range- Isolated

van Dyk & Slotow, 2003

Rhodes & Rhodes, 2004

Direct observations supplemented with patrol data

Unsystematic

Do patterns of prey selection support earlier findings from Save Valley Conservancy?

What influence do perimeter fences have on prey selection? Do fence-impeded kills comprise a greater proportion of

larger prey species and prime age animals than those that are not fence-impeded?

Is the physical condition of prey better among fence-impeded kills?

Do wild dogs spend more time actively hunting in close proximity to fences so at to maximise the advantage they confer?

RESEARCH QUESTIONS

STUDY AREAVENETIA LIMPOPO NATURE RESERVE

STUDY AREAVENETIA LIMPOPO NATURE RESERVE 320 km2

Mopane biome Predator-proof fence to contain

populations of large herbivores, carnivores

Reintroduced population 16 individuals (9+7) in

January 2002 Member of the national wild

dog metapopulation

STUDY POPULATIONVENETIA LIMPOPO WILD DOG PROJECT

Jan-02 Jan-03 Jan-040

5

10

15

20

25

30

Date

Pop

ula

tion

siz

e

METHODSWILD DOG DIET

VHF collars (2-5 individuals)Intensive radio-tracking, 2002-2004

Activity periods - crepuscular 5-day continuous follows - overnight Tourism trips

METHODSWILD DOG DIET Direct observations of kills

Date and time Location Species Age (tooth wear) Sex (adults and sub adults only) Femur marrow condition

Visual score, % marrow fat Compare with venison hunts

Estimated edible biomass Allocated size category

Small <25 kg Medium 25-90 kg Large >90 kg

Distance from fence line, fence-impeded or not

METHODSCATCH PER UNIT EFFORT Straight-line distance of kill

from pack’s previous resting location Includes hunting AND

traversing

Catch per unit effort measured in kg/km

METHODSZONE USE Perimeter fence buffered

Number of locations compared to proportional area Activity vs. resting

Exclude denning season locations

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5 0 5 KilometersDiamond mine0-1 km from fence1-2 km from fence2-3 km from fence3-4 km from fence4-5 km from fence>5 km from fence

# Venetia Pack locations

N

RESULTSBRIEF SUMMARY 392 kills in 3 years

Sub-sample of 316 for this fence analysis

0.41 kills/activity period (n=723)

Kill rates were correlated to pack size

Per capita consumption was 2.09 kg/dog/day

Impala accounted for 78.1% of dietary items

Only juveniles of larger species were taken (eland, gemsbok, wildebeest) and only rarely

41% of kills were fence-impeded

RESULTSKILL LOCATIONSLarge kills: >90kg, solid circles

Medium kills: 25-90 kg, empty circles

Small kills: <25 kg, crosses

Den sites: squares

n=316

PREY CONDITION

RESULTSSURVIVAL OF THE FITTEST?

PREY AGE

Denning(Jun-Aug)

Post-den-ning(Sep-Nov)

Lamb-ing

(Dec-Feb)

Pre-den-ning(Mar-May)

0.40

0.60

0.80

1.00

1.20

1.40 Popu-lation

Season

Tra

nsf

orm

ed %

marr

ow

fat

Hunted(n=25)

Wild dogkills

(n=60)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

>765

Pro

port

ion

in

each

tooth

wea

r ca

tegory

Juvenile impala killed less frequently on the fence

Adult female kudu killed more frequently on the fence

Adult and sub adult male kudu killed more often on the fence but sample sizes are too small

RESULTSPREY SPECIES

Sex AgeNot fence-impeded

Fence-impeded

Ratio TotalProportio

n on fence

No. Prop. No.Pro

p.Impala Female Adult 32 0.17 18 0.14 0.8 50 0.36

Sub adult 8 0.04 4 0.03 0.7 12 0.33> Juvenile 2 0.01 0.0 2 0.00Unknown 3 0.02 1 0.01 0.5 4 0.25

Male Adult 22 0.12 13 0.10 0.9 35 0.37Sub adult 5 0.03 3 0.02 0.9 8 0.38Unknown 1 0.01 0.0 1 0.00

Unknown Adult 2 0.02 - 2 1.00

Unknown 5 0.03 4 0.03 1.2 9 0.44

All Juvenile 30 0.16 6 0.05 0.3 36 0.17Kudu, Greater Female Adult 11 0.06 29 0.23 3.9 40 0.73

Sub adult 7 0.04 7 0.05 1.5 14 0.50Unknown 1 0.01 - 1 1.00

Male Adult 1 0.01 5 0.04 7.3 6 0.83Sub adult 1 0.01 4 0.03 5.9 5 0.80

Unknown Adult 1 0.01 0.0 1 0.00

Unknown 1 0.01 - 1 1.00

All Juvenile 9 0.05 8 0.06 1.3 17 0.47Bushbuck 5 0.03 1 0.01 0.3 6 0.17Cow 1 0.01 - 1 1.00Duiker, Common 8 0.04 4 0.03 0.7 12 0.33Eland 1 0.01 0.0 1 0.00Gemsbok 4 0.02 1 0.01 0.4 5 0.20Hartebeest, Red 2 0.01 0.0 2 0.00Jackal 1 0.01 0.0 1 0.00Steenbok 8 0.04 5 0.04 0.9 13 0.38Warthog 11 0.06 5 0.04 0.7 16 0.31Waterbuck 8 0.04 4 0.03 0.7 12 0.33Wildebeest, Blue 2 0.01 1 0.01 0.7 3 0.33Total 188 1.00 128 1.00 1.0 316 0.41

RESULTSPREY SIZE Greater proportion of large

prey caught on the fence (2=33.05, p<<0.001)

Median mass of fence-impeded kills > than unimpeded kills, 32.9 vs. 25.0 kg (W=25667.0, p<<0.001)

Fence-impeded kills comprised 54.1% of total edible biomass captured

Edible biomass was the most significant variable in predicting whether a kill was fence-impeded or not (positive)

Small (<25 kg)

Medium (25-90 kg)

Large (>90 kg)

0

20

40

60

80

100

Not fence-impeded Fence-impeded

Size class

Nu

mber

of

kil

ls

RESULTSPREY SEX, AGE & CONDITION Proportion of males and

females killed on fence did not differ for impala or kudu

Adult impala males killed on the fence had higher % marrow fat than those killed away from the fence (Mann-Whitney, W=111.0, p=0.012, n=28)

Kudu males killed on fence had highest % marrow fat of all, but small sample sizes

RESULTS CATCH PER UNIT EFFORTUn-

impededCriterion Fence-

impeded

2.9 Mean distance from resting to kill

(km)

2.5

12.2 Median catch per unit effort (kg per

km)

27.3

1 2 >30

20

40

60

80

100

120

140

Periods to next kill

Kil

ogra

ms

con

sum

ed d

uri

ng

curr

ent

act

ivit

y per

iod

Important consequences:

Biomass consumed per activity period influences inter-kill interval

Hunting is risky!

RESULTSZONE USE DURING ACTIVITY PERIODS

Zone(distance from fence in km)

Area(km2)

Proportion of total

reserve area

Number of active

locations

Proportion of active locations

Preference index(PI)

Normalised preference

index(Log10[PI+1]

)

0-1 8,108 0.26 97 0.66 2.55 0.551-2 6,518 0.21 23 0.16 0.75 0.242-3.5 6,544 0.21 14 0.09 0.46 0.163.5-5 4,905 0.16 9 0.06 0.39 0.14>5 5,507 0.17 5 0.03 0.19 0.08Total 31,582 1.00 148 1.00 1.00  

The pack was also more likely to be found closer to the perimeter fence when active than when resting (χ2= 7.94, p=0.047, 3 d.f.)

RESULTSSECONDARY IMPACTS ON PREY POPULATIONS

12 confirmed breaches in 723 follow periods 4 kudu 3 impala 1 juvenile zebra 1 steenbok 3 unidentified

More suspected!

Fence-impeded killsSpecies Different species

composition (e.g. kudu females)

Size Greater biomass per kill

Age More adults (impala, kudu)

Sex No difference for main prey species

Body condition

Better condition (e.g. adult male impala)

Shorter chase distances

Greater catch per unit effort

Fewer hunting forays

RESULTSOVERALL SUMMARY

Benefits for AWDs

Fitness benefits?- Survival?- Reproduction?

POSSIBLE FITNESS BENEFITS?

Davies-Mostert, 2010

* Includes data from all reserves, even those where fence-hunting is uncommon

Wild dog predation is at least partly compensatory

Supports SVC “survival of the fittest” study

Wild dogs actively make use of fences as a hunting tool

Supports earlier studies in SA

Fences cause shifts in patterns of prey selection with potential shifts in predator-prey dynamics

Potentially reduces the compensatory nature of predation

Consequences for the ability of small reserves to support predator populations in the long-term

CONCLUSIONS &MANAGEMENT IMPLICATIONS

Magriet van der Walt Melanie Boshoff Herta Martin Lynda Hedges Richard Selamolela and Venetia scouts Kath Potgieter Pat Fletcher Graham Main Warwick Davies-Mostert Lesley Sutton Many others!

ACKNOWLEDGEMENTS