Managing Kruger s Elephants: the Metapopulation Metaphor Rudi van Aarde, Sam Ferreira, Tim Jackson & Adrian Shrader Supported by postgraduate students Conservation Ecology Research Unit University of Pretoria South Africa Rudi van Aarde
Supporting agencies (2003 to 2005) Bateleurs Botswana Dept. Wildlife & National Parks Conservation International Conservation Fund Zambia Conservation Lower Zambezi Direcção Nacional de Areas de Conservação, Mozambique International Fund for Animal Welfare Kalahari Conservation Society Mozal Community Development Trust National Research Foundation Namibian Min. Tourism & Environment National Postcode Lottery, Netherlands Malawian Wildlife Department Peace Parks Foundation South African National Parks US Fish & Wildlife Services University of Pretoria WWF South Africa Zambian Wildlife Authority
Conservation management of elephants Urgent but controversial. Driven by personal opinion and experience. Often motivated by selective interpretation of information. Conservation measures for ex situ and in situ populations differ.
Immigration Births Population Deaths Emigration
Immigration Transfrontier parks Contraception Culling Births Population Deaths Transfrontier parks Emigration
Births Immigration Metapopulation Metapopulation Population Metapopulation Metapopulation Emigration Deaths
The Metapopulation Approach A collection of populations of the same species. Dynamics of these populations are asynchronous. Dispersal occurs between populations.
Time (t) Time (t + 1)
Angola Zambia Malawi Mozambique Zimbabwe Namibia Botswana South Africa
Linear Spatial Model 0.5d i 0.5d i N i-1 N i N i+1 0.5d i-1 b i m i 0.5d i+1 N i, t+ 1 = Ni, t + 0.5di 1Ni 1, t 0.5di Ni, t + bi Ni, t mi Ni, t 0.5di Ni, t + 0. 5di+ 1Ni+ 1, t N n j, i i, t+ 1 = Ni, t + bi Ni mi Ni + N j j= 1 n d d i N i
7 6 5 4 3 2 1 0 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 0 20 40 60 80 100 Time (Years) Density (n.km -2 ) Regional Density (n.km -2 )
The benefits of the metapopulation approach Allows for the natural limitation of populations regionally. Provides opportunity for habitat regeneration. Provides regional conservation management opportunities.
Kruger s elephants as a metapopulation? Avoid the asymptote syndrome. Need an uneven distribution and density of elephants. Vacant habitats available. Maintain natural forces limiting numbers. Metapopulation dynamics needs space and time. Map provided by SANParks
Kruger s elephants as a metapopulation? Avoid the asymptote syndrome. Need an uneven distribution and density of elephants. Vacant habitats available. Maintain natural forces limiting numbers. Metapopulation dynamics needs space and time. Map modified from Whyte 2004
Response to culling population growth rate 0.3 0.2 0.1-0.0-0.1-0.2 12 13 8 5 4 13-0.3-2 -1 0 1 2 3 4 5 Years after culling From:- Van Aarde et al. 1999, Animal Conservation 2, 287-294.
Range use in Kruger 95% MCP for 48 elephant cows (1980 1996) From Grainger, 2003 MSc thesis, UP Rudi van Aarde
Home range areas for elephants across Kruger National Park Home range size (km 2 ) 3000 2000 1000 0 n=36 0 10 20 30 40 50 Artificial water resource richness density (number per 100km 2 ) From Grainger, van Aarde & Whyte (accepted)
Population numbers - Kruger National Park - Number of elephants 12000 10000 8000 Culling 6000 1965 1975 1985 1995 2005 Year Van Aarde et al. 1999, Animal Conservation 2, 287-294. Whyte et al. 2003. The Kruger experience Tim Jackson
Population variables - Kruger National Park Variable Onset of culling era (1974-78)* Late culling era (1990-94)* Post culling era (2004) Calving interval 4.01±0.19 4.02±0.11 3.05±0.09 First calving 12.41±0.38 12.82±0.03 9.73±0.26 Survival (calves) 0.983±0.005 0.957±0.003 0.979±0.005 S 2-4 (Young) 0.983±0.005 0.956±0.004 0.980±0.003 ** Raw data from Ian Whyte, SAN Parks (in litt.) All values followed by one S.E. of the mean From Ferreira & van Aarde in prep.
Population trend in Kruger National Park (1984 2003) Number of elephants 12500 10000 7500 r=1.13±0.34% r=3.85±0.85% 5000 1985 1990 1995 2000 2005 Year r=11.2±0.02% Data from Ian Whyte, SAN Parks (in litt.) Rudi van Aarde
15.0 12.5 Age at first calving 10.0 7.5 5.0 2.5 Ferreira, Shrader & van Aarde in prep. Young Short High Rudi van Aarde Etosha Okavango Moremi Chobe Kafue L. Zambesi Vwaza Kruger Tembe Maputo Addo 0.0 5 Calving interval 4 3 2 1 Etosha Okavango Moremi Chobe Kafue L. Zambesi Vwaza Kruger Tembe Maputo Addo 0 1.25 1.00 Calves surviving (prob) 0.75 0.50 0.25 Etosha Okavango Moremi Chobe Kafue L. Zambesi Vwaza Kruger Tembe Maputo Addo 0.00
Yearly Intrinsic Population Growth Rate - Southern African Elephants - 0.07 0.06 Intrinsic population growth rate 0.05 0.04 0.03 0.02 0.01 0.00 Etosha Okavango Moremi Chobe Kafue L. Zambesi Vwaza Kruger Tembe Maputo Addo From Ferreira, Shrader & van Aarde in prep.
How do we overcome the problem? Allow survival and reproduction to be limited. Stop tampering with resources that limit populations. Restore population limitation through metapopulation dynamics. Rudi van Aarde
Angola Zambia Malawi Mozambique Zimbabwe Namibia Botswana South Africa
When there is little evidence available, doing nothing might sometimes be the best worst option, however politically unacceptable this might seem. Griffiths, R.A. (November 2004). Trends in Ecology and Evolution 19: 464-465.
Geo-political delineation of TFCA across southern Africa