Females With Fake Penises

Female spotted hyenas have perhaps the most unusual reproductive anatomy of any mammal: an enlarged clitoris that looks almost identical to a male's penis, often called a "pseudo-penis."

This structure is about 7 inches long and can become erect. Females urinate, mate, and even give birth through this narrow tube. Unfortunately, this makes childbirth extremely difficult and dangerous — the birth canal runs through the pseudo-penis, and first-time mothers have a high mortality rate. Cubs also face risks: about 60% of first-born cubs suffocate during the long journey through this narrow canal.

So why did this evolve? Female spotted hyenas have unusually high levels of testosterone — higher than males in many cases. This makes them larger, more aggressive, and socially dominant over males. The pseudo-penis is a side effect of this hormonal environment.

The high testosterone also affects behavior: spotted hyenas live in matriarchal societies where females outrank all males. Even the lowest-ranking female dominates the highest-ranking male. This is extremely rare in mammals.