Low demographic variability in wild primate populations: Fitness impacts of variation, covariation, and serial correlation in vital rates

Background/Question/Methods

In a stochastic environment, long-term fitness can be influenced by variation, covariation, and serial correlation in vital rates (survival and fertility). Yet no study of an animal population has parsed the contributions of these three aspects of variability to long-term fitness. We do so using a unique database that includes complete life history information for wild-living individuals of seven primate species that have been the subjects of long-term (22 to 45 year) behavioral studies. We compared estimated variances of adult survival in primates to values for other vertebrates in the literature.

Results/Conclusions

Overall, the estimated levels of vital rate variation had only minor effects on long-term fitness, and the effects of vital rate covariation and serial correlation were even weaker. In fact, we found adult survival to be significantly less variable in primates than in the other vertebrates. We found only mixed support for the prediction from stochastic life history theory that adult survival, because it more strongly influences fitness in a constant environment, will be less variable than newborn survival. Our results suggest that wild primates may be buffered against detrimental fitness effects of environmental stochasticity by their highly developed cognitive abilities, social networks, and broad, flexible diets.