Hyena androgens exact high cost

From Bloomington, Ind., at a meeting of the Animal Behavior Society

The latest chapter in a study of spotted hyenas reveals the burdens that the species’ unusual androgen hormones impose on females.

In more typical mammals, males slosh around in a testosterone world, but in spotted hyenas, females get big doses of testosterone derivatives, too, starting in their mother’s womb. In a long-running project at the University of California, Berkeley scientists are investigating the role of these hormones in the females’ aggression, social dominance, and malelike anatomy. The clitoris of a female spotted hyena typically grows into a long, penislike structure, through which the animal urinates, receives semen, and gives birth.

Researchers at Berkeley treated five pregnant females with compounds that blocked the formation and function of testosterone and its chemical derivatives, then followed the male and female pups.

The four female pups still turned out to have their elongated organ, so the researchers conclude it’s not just a result of the hormones. The male pups ended

up with shorter-than-normal, round-tipped penises, shaped like the female organ.

All the female pups have grown up to have their own first litter, reports Christine Drea of Duke University in Durham, N.C. All pups from the androgen-deprived mothers survived birth. In a matched set of young females with normal hormone exposure and physiology, 60 percent of the first litter of pups suffocated while passing through the mother’s elongated clitoris. Drea speculates that low androgen exposure changed such genital qualities as elasticity.

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.

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