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Keywords:

  • demography;
  • population structure;
  • individual-based model;
  • population dynamics;
  • sensitivity analysis;
  • Elephas maximus

Abstract

Demographic models are important tools for assessing population status, diagnosing potential causes of population decline, and comparing management strategies that might change population trajectory. The population of Asian elephants (Elephas maximus) maintained in North American zoos has been declining for the past decade, and Wiese ([2000] Zoo. Biol. 19:299–309) predicted a continued decline in the population using an age-based matrix model. We developed an individual-based model to further explore the demographic issues of the population. Our model allowed us to quantitatively evaluate the prospects for slowing or reversing the decline given the potential management strategies of improving reproduction, reducing infant mortality, altering birth sex ratio, and recruiting additional individuals from outside the population. Our simulations showed that if current demographic trends continued, the population would continue to decline at 2%/year. It was possible to create sustainable simulations, but these required a large increase in the annual number of births produced. Increasing reproduction was the most effective strategy to slow the decline, whereas other management strategies had the most impact when combined with increases in reproduction. Almost all simulations resulted in large changes in population structure, with increases in the male population and decreases in the female population. Given the population's demographic issues, it will be difficult to either increase the population substantially or sustain it at its current size. Zoo Biol 25:201–218, 2006. © 2005 Wiley-Liss, Inc.