Mammalian Sibling Rivalry

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The occurrence of sibling rivalry has now been documented in many species of animals, including humans. Mammalian sibling rivalry is widely believed to be less deadly than that among avian brood mates. The broad goal of the current research is to evaluate the generality of existing sibling rivalry theory by exploring sibling conflict in mammals. The work will focus specifically on one species of gregarious mammal, the spotted hyena, in which sibling rivalry is more intense than is that described in other mammals. A combination of techniques, including behavioral observation, monitoring of excreted hormone levels, and fetal ultrasonography, will be used to determine whether siblicide occurs facultatively or obligately in free-living hyenas in Kenya. The influence of hormones on dispersal will also be addressed.Siblings are often each other's closest associates and closest competitors, so they often bear the heaviest costs of selfish behavior. Because the best interests of rival siblings need not necessarily coincide with those of their parents, conflict between parents andoffspring often affects the form and outcome of sibling competition. The study of sibling rivalry is thus of great significance for understanding the occurrence of both selfish and altruistic behaviors among close kin in our own species and in other animals.