Hyena females are considerably larger than the males. The females are masculinized due to the excess testosterone in their bodies; they have more testosterone in their bodies than most male hyenas. As a result of this masculinization, females are a third larger than the males, have more muscle mass, are more aggressive, and have masculinized genetalia. Their vulva is fused to look like a scrotum and testes, and their clitoris is large and looks like a phallus, and can be erected just like a penis. The vagina runs through the pseudo penis. This makes it hard for them to mate and give birth, since they do so through this pseudo penis. It was once thought that hyenas were hermaphroditic animals because the females sported genitalia similar to the males. In fact, the only sure way to determine the sex of a hyena is that after giving birth the female's two black nipples become enlarged.

The erect 'penis' of both sexes plays a prominent role in ritualized greeting