Little is currently known about how prenatal exposure to androgenic hormones influences aggressive behavior in adult mammals, or about how variation in early androgen exposure ultimately affects survival and reproduction. We propose to investigate these questions using spotted hyenas as subjects. In striking contrast to other female mammals, female spotted hyenas are bathed in the womb with high concentrations of androgens, which are traditionally thought of as male hormones. Interestingly, spotted hyenas are also sex-role reversed relative to other mammals, in that females are far more aggressive than males. Spotted hyenas are therefore ideal model organisms for studying effects of early androgen exposure on the development of aggressive behavior, its neural and hormonal mediation in adulthood, and its fitness consequences. A large-scale experiment is under way in which female spotted hyenas are treated throughout pregnancy with anti-androgens, and the offspring resulting from those pregnancies are later evaluated as adults, with respect to their aggressive behavior, nervous system, and reproductive tract. Availability of the captive hyenas also permits researchers to test the "social brain" hypothesis, which suggests that the evolution of large brains and great intelligence were favored in primates by selection pressures associated with life in complex societies. If so, then cognitive abilities and nervous systems with primate-like attributes should have evolved convergently in non-primate mammals living in large, elaborate societies, in which social dexterity enhances individual fitness. The societies of spotted hyenas are remarkably similar to those of old-world primates with respect to size, structure, and patterns of competition and cooperation. These similarities set the stage for a unique comparative analysis of cognition and neural organization, utilizing a social carnivore. In addition to shedding significant new light on the neural mediation of both aggression and intelligence, this research offers unique training opportunities for undergraduates, graduate students, and postdoctoral scientists in the areas of neuroendocrinology, comparative endocrinology, behavioral neuroscience and cognitive science
