Dynamic Science in the Somali Wild Ass

With a wild population size estimated at less than 600 individuals, the Somali wild ass is a critically endangered species. Approximately 30 individuals reside in U.S. zoos, with about a third of these animals living at the Wild Animal Park. 

The primary goal of this project is to provide a scientific framework for understanding factors influencing differential reproductive success among individuals by conducting a detailed study of social behavior and hormone concentrations. The non-invasive use of fecal steroid analysis offers a novel means of examining the reproductive biology in the wild. 

Maintaining a sustainable population in zoos is dependent upon a more complete understanding of the social dynamics and reproductive endocrinology of individuals within a herd. The study will involve collection of observational data on all animals, as well as collection of fecal samples from animals of differing sex, age, and reproductive status.

Among the key issues that we plan to address are age of reproductive maturation in females, effect of maternal rank on male hormone and behavioral development, influence of endocrine state on social affiliation, maternal competence and experience/hormone concentration, maternal effort and sex of offspring, role of sexual coercion in reproductive profiles, and the effect of calf development on resumption of estrous cycling.