Viability of the Serengeti Cheetah Population

Abstract

AbstractMost recent population viability analyses, especially those of long‐lived species, rely on only a few years of data or data from a closely related species, combined with educated guesswork, to estimate model parameters and the variability surrounding those measures. This makes their conclusions or predictions difficult to evaluate. In our study, we used 20 years of demographic data on Serengeti cheetahs (Acinonyx jubatus) to conduct a population viability analysts. First we constructed a model of the deterministic growth rate and found that the cheetah population is nearly self‐replacing (λ = 0.997). Our model showed that population growth was most strongly influenced by adult survival, followed by juvenile survival, which is typical of long‐lived, iteroparous species. We then examined extinction risk and long‐term projections of cheetah population size with our stochastic model, Popgen. We compared the projections with over 20 years of field data and found that demographic stochasticity trials produced a stable population size, whereas environmental stochasticity trials were slightly more pessimistic. Extinction risk was highly sensitive to both adult survival and juvenile survival (from 0‐1 years). Decreasing the variance in survival rates also decreased extinction risk. Because lions are the major predator on cheetah cubs, we used our demographic records to simulate the effect of different lion numbers on juvenile survival. High lion abundance and average lion abundance resulted in extinction of nearly all cheetah populations by 50 years, whereas with low lion abundance most cheetah populations remained extant. Conservation of cheetahs may not rely solely on their protection inside national parks, but may also rely on their protection in natural areas outside national parks where other large predators are absent.