Army ant population dynamics: the effects of habitat quality and reserve size on population size and time to extinction

Abstract

A simple deterministic model is used to examine the effects of habitat size and quality upon the sizes and chances of extinction of isolated populations of a species of neotropical army ant, Eciton burchelli . The results of the model suggest that equilibrium population size is influenced more by habitat size than quality. Similarly, expected extinction times increase exponentially with habitat size but depend on quality only through its minor effects upon the equilibrium population size. Such effects may be crucial from a conservation point of view, however, because of the strong dependence of extinction probabilities on equilibrium population size. Density-independent effects in the form of queen senescence also have strong effects on expected extinction times but not on equilibrium population size. The results are used to predict which of several islands and peninsulas in and around Gatun Lake, Panama, have a high probability of still being populated by E. burchelli after their isolation from the surrounding tropical rain forest.