Hyenas' Top Dog Status Begins in the Womb

Nicholas Bakalar
for National Geographic News
April 26, 2006

High levels of male hormones known as androgens might explain how higher-ranking female hyenas pass on dominant status to their offspring, according to a new study.

In spotted hyenas both male and female cubs exposed to an extra dose of androgen in the womb begin engaging in more aggressive behavior soon after birth.

Male cubs engage in more sexual play, such as mounting, than the females. But extra maternal androgens are associated with higher rates of aggression and mounting in both sexes, the study finds.

Cub aggression, however, is not necessarily higher among offspring of high-ranking mothers, the study says.

The study is to be published in tomorrow's issue of the journal Nature.

"Basically what the analysis indicates is that, while some of the differences among individuals in levels of aggressive and sexual play in cubs can be predicted solely by the mother's dominance status, there are still important differences in levels of these behaviors that can only be accounted for by the levels of androgen the cubs experienced while in utero," said lead author Stephanie M. Dloniak of Michigan State University.

The research was carried out on wild hyenas at the Masai Mara National Reserve () in Kenya from 1993 to 2002.

The researchers measured hormone concentrations in the animals' fecal samples. The work revealed that higher ranking females had higher androgen levels than low-ranking females. The effect was apparent in their cubs.

Hierarchical Society

Hyena society is rigidly hierarchical, and higher ranking members are the ones with first access to food.

Within a pack, females vary widely in rank, but all adult females are socially dominant to all adult males. Females are larger than the males and more aggressive.

Unlike the females of most social carnivore species, all the females among spotted hyenas produce offspring, but the higher ranking females have a longer reproductive life and more litters.



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