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

Abstract

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/mile 2 . 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 mile 2 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.