You dont find many mammals where the female is the boss, Holekamp said.
The sex roles in spotted hyenas are completely reversed from those in most mammals: females are larger and more aggressive than males when competing for limited resources and dominate the 40 to 60 members of their social group.
In fact, females look so much like males the average person may have trouble differentiating between the sexes. A female hyenas genitals have evolved into something that looks more like a penis than a vagina.
Holekamp and her colleagues speculate that the behaviors attributed to exposure to high levels of prenatal androgens may be evolutions way of offsetting the negative consequences associated with mating and giving birth through a penis-like structure.
A spotted hyenas vaginal canal makes a hairpin turn and exits the body like a penis. The opening of the vaginal canal is at the end of an elongated clitoris, nearly six to seven inches in an adult, that looks remarkably like a penis, Holekamp said.
Not surprisingly, ancient people, like the Greek philosopher Aristotle, thought hyenas were hermaphrodites.
The characteristics of the genitalia are responsible for some obvious anatomical challenges that arise when its time for a hyena to mate and give birth.
Mating is tricky to say the least. A male must position himself at just the right angle to enter the females clitoris. If the match is successful, a mother hyena will give birth to each of her 2-pound cubs through the elongated clitoris, which doubles its diameter from one to two inches for the occasion.
Its really weird genitalia, but it seems to work. Although giving birth through a penis isnt a trivial problem. Holekamp said. All her female-typical behaviors are there shes been masculinized without being defeminized.
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Contact: Kay Holekamp
Holekamp@msu.edu
517-432-3691
Michigan State University
26-Apr-2006