A Population Viability Analysis for African Elephant (Loxodonta africana): How Big Should Reserves Be?

We present an age-structured, density-dependent model of elephant population dynamics in a fluctuating environment, drawing primarily upon the life history parameters obtained from studies in semi-arid land at Tsavo National Park, Kenya. Density regulation occurs by changes in the age of first reproduction and calving interval. We model environmental stochasticity with drought events affecting sex- and age-specific survivorships. Results indicate a maximum population growth rate of 3% per year and an equilibrium elephant density of 3.1/mile2. Analysis of the demographic results and their sensitivity to changes in juvenile survivorship and drought frequencies, supported by genetic considerations, suggests that in semi-arid regions a minimum reserve size of 1000 mile2 is necessary to attain a 99% probability of population persistence for 1000 years. The effect of age-independent culling on population viability is also analyzed.

[1]  An assessment of the maximum sustainable yield of ivory from African elephant populations. , 1991, Mathematical biosciences.

[2]  G. Caughley,et al.  Projected decline of the African elephant , 1990 .

[3]  Georgina M. Mace,et al.  Assessing Extinction Threats: Toward a Reevaluation of IUCN Threatened Species Categories , 1991 .

[4]  William H. Press,et al.  Book-Review - Numerical Recipes in Pascal - the Art of Scientific Computing , 1989 .

[5]  CHARACTERIZING STABLE POPULATIONS: AN APPLICATION TO THE AFRICAN ELEPHANT POPULATION' , 1973 .

[6]  R. Malpas.  Elephant Losses in Uganda – and Some Gains , 1981, Oryx.

[7]  R. Laws.  Elephlants as agents of habitat and landscape change in East Afica. , 1970 .

[8]  R. Lande.  Genetics and demography in biological conservation. , 1988, Science.

[9]  T. Corfield.  Elephant mortality in Tsavo National Park, Kenya , 1973 .

[10]  R. Barnes.  The elephant problem in Ruaha National Park, Tanzania , 1983 .

[11]  D. Cumming.  The Influence of Large Herbivores on Savanna Structure in Africa , 1982 .

[12]  R. Laws.  The Tsavo Research Project , 1970, Oryx.

[13]  P. H. Leslie.  THE INTRINSIC RATE OF INCREASE AND THE OVERLAP OF SUCCESSIVE GENERATIONS IN A POPULATION OF GUILLEMOTS (URIA AALGE PONT.) , 1966 .

[14]  J. Phillipson.  Rainfall, primary production and ‘carrying capacity’ of Tsavo National Park (East), Kenya , 1975 .

[15]  M. Soulé,et al.  Benign neglect: A model of faunal collapse in the game reserves of East Africa , 1979 .

[16]  S. Stuart,et al.  African Elephants and Rhinos: Status Survey and Conservation Action Plan , 1990 .

[17]  L. S. Wu,et al.  Of Elephants and Men: A Discrete, Stochastic Model for Long-Lived Species with Complex Life Histories , 1980, The American Naturalist.