DEMOGRAPHIC CONSEQUENCES OF LIFE HISTORY VARIATION IN NONHUMAN PRIMATES (POPULATION ECOLOGY, LESLIE MATRIX)

The delay in age at maturity associated with increased behavioral flexibility and prolonged life span in nonhuman primates is a potential demographic trap. In order to offset the lower reproductive rates and longer generation times, long-lived species must alter other aspects of their life histories. The purpose of this research is to demonstrate a method for measuring the demographic effects of such a change in life histories on population compositions and population growth rates among the nonhuman primates. A Leslie matrix projects stable population distributions and population growth rates. These projections are compared with census data or survivorship data from several species of nonhuman primates by analysis of angular divergence of vectors, comparison of sample populations to confidence intervals around a reference vector, and comparisons of cumulative survivorship that the stable population vectors represent. Most fluctuation in survivorship had little impact on the population growth rate and composition between trials. A significant effect was produced by extending reproduction for at least one age class, and the combination of extension of the reproductive span and increased infant survival produced large differences among projections. The extension of the reproductive span beyond that expected on the basis of a proportional extension of all life cycle stages is the way out of the demographic trap for members of the Order Primates