The core of many animal societies is the mating system, which is built upon the amicable and aggressive relationships that develop between reproductive males and females. But reproductive units are themselves often organized into larger social groups thus creating layers in animal societies. Dr. Rubenstein will examine these issues in the multilevel society of plains zebras (Equus burchelli), a grazing mammal of the East African savanna ecosystem. The mating system of plains zebras consists of year-round harems in which females and their young offspring live with one dominant male. These reproductive groups often associate with other similar groups or with subadult males. Therefore, the plains zebra is an ideal species to examine the structure and function of societies with multiple levels of organization. Dr. Rubenstein will determine why higher level associations form and persist; and he will determine how they act as coordinated units. Long-term movements and associations of individually recognizable zebras will be monitored in relation to underlying variation in environmental factors such as vegetation quality and predator risk. Leadership and following decisions of individuals within core groups, and resolution of conflicts among individuals with differing interests will elucidate the trade-offs involved in this social system.
The overall result of the study will be a better understanding of the dynamics of complex societies that are often hierarchically structured--but much less visibly than those of zebras where membership in a core group restricts total freedom of movement within a society at large. In addition to elucidating these general 'rules' of social organization data on zebra abundances, distributions and patterns of recruitment in relation to ecology and social organization will have important applications for managing wildlife in sustainable ways.
