Exploring the Roles of Competition and Constraint in the Evolution of Mammalian Behavior

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Little is currently known about how the physical development of a young mammal interacts with social and ecological forces at work in the youngsters environment to affect, not only its own performance in ecologically important tasks, but also the behavior exhibited by its parents. This research will investigate this interaction in carnivorous mammals that consume hard foods like bones. The ability to ingest hard foods requires a relatively massive skull that can withstand forces that might otherwise lead to bending or breakage of the bones of the head and jaws. The research will test an hypothesis suggesting that this type of unusually robust skull takes an exceptionally long time to develop as young carnivores mature, that this slow development prevents youngsters from optimizing feeding performance at a young age compared to species that eat softer foods, and that compensatory parental behavior evolves as a consequence so parents can help their young feed until the skull is more fully formed. A second hypothesis that will be tested suggests that the effects of slow skull development are exacerbated by the social environment in which the youngster must feed itself. Specifically, when feeding competition is intense, extreme compensatory adaptations may be expressed in parents. By combining field and laboratory studies, these hypotheses will be tested with a comparative analysis of skull development, feeding performance, feeding competition, and parental behavior in two bone-crushing species, the spotted hyena and the striped hyena. Spotted hyenas are gregarious and their feeding competition is intense, but striped hyenas are solitary. The patterns of development in morphology and performance will be compared in these two hyenas with those in several other carnivores that are not adapted for crushing bones. This work will provide a great deal of information about the evolutionary relationship between morphological development and behavior. The study will also generate much new information about the biology of the striped hyena, one of the few large carnivores about which very little is currently known. The study will thus fill a major gap in carnivore biology, and provide critical information for the conservation of these animals. Furthermore, this research will continue to train American and Kenyan graduate students, teach a study abroad course each year on the behavioral ecology of African mammals, and offer U.S. undergraduates unique opportunities to gain research experience at the interface between behavior and morphology.This award is co-funded by the Office of International Science and Engineering