Modelling elephant population growth in small, fenced, South African reserves

Elephants have been, and continue to be, introduced to small conservation areas in South Africa despite concerns that elephants may adversely affect the vegetation for other herbivores, reduce the aesthetic value of the landscape for tourism, and fundamentally reduce local biodiversity. The rate at which elephant populations grow is essential knowledge for elephant management. We examined growth rates of elephant populations introduced to eight small reserves in South Africa, determined demographic parameters (age at sexual maturity, calving interval, sex ratio at birth, and age-specific probabilities of conception and survival) for each population, and made short-term projections of future population growth based on these parameters and the current population structure. Average annual population growth rates following introduction ranged from 5 to over 10%, and are projected to be in the range of 6.2 to 8.9% over the duration of the next 20 years. Model projections suggest that populations can double in less than 10 years, that calving interval is the most important demographic factor determining population growth rate, and that the structure of the introduced population will greatly influence future growth. Without active management to reduce or maintain population sizes in the next few years, small reserves throughout South Africa will undoubtedly experience overpopulation of elephants within 10 to 20 years. Population growth rates of elephants in new areas and on the short term can be much higher than expected from large, established populations.