Spotted Hyena
Crocuta crocuta
Female Dominance

Image courtesy of Jack Haverty

It is characteristic of most social carnivores and even mammals to be patriarchal/dominated by the males. Spotted Hyenas are set apart from social carnivores and most mammals because they are matriarchal/dominated by the females (Frank 1986). This is most obviously explained by the females' strongly masculinized genitalia, isomorphism of body size and high levels of circulating androgen in both adults and fetuses. But why female dominance? Frank cites that one argument is that protection of cubs agains predation by males may be the function of female dominance, but there is no evidence that males kill juveniles, so there must be another reason. Frank suggests that a prominent function of female dominance is to ensure adequate nutrition to both lactating females and their dependent young. This makes sense evolutionarily because the more aggressive females could out compete others for food and be more successful in rearing cubs because of their own elevated nutrition and their success in making sure their offspring get food. Frank further suggests that increasing female aggressiveness was mediated in part by rising levels of androgen, and high levels of androgen directly affects rank and aggression levels. Muller and Wrangham did a study in 2002 that doesn't necessarily counter this proposal, but brings some new information to light. After a series of experiments, they found that contrary to expectation, female spotted hyena genitals develop their typical masculine form even in the absence of androgenic steroids. They still maintain the possibility that it may have began as an incidental consequence of high androgen levels in females providing the opportunity for selection to act. Regardless, the increase in aggression of females increased the success in raising offspring which most likely drove selection for aggressive females further, leading to eventual dominance over males.

This web site was created by Keeley Roles for an undergraduate class, Animal Behavior, at Davidson College Spring Semester 2004. Email keroles@davidson.edu with questions regarding this web page.

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