The Sealed-Off Females

Female European moles are some of the most unusual mammals alive — they're essentially intersex by design.

Their gonads are called ovotestes: part ovary, part testis. The testicular portion produces testosterone, giving females hormone levels that rival males.

This high testosterone makes female moles: - Extremely aggressive and territorial - Powerful diggers capable of defending tunnel networks - Unwilling to tolerate other moles, including males, most of the year

The vaginal situation is equally unusual. Most of the year, females have no external vaginal opening at all — their genitals are masculinized with an enlarged clitoris.

Only when breeding season arrives (and testosterone dips slightly) does a vaginal opening develop, allowing mating.

Males must be brave to approach. Female moles will attack males who enter their territory outside the brief breeding window. The absent vagina isn't just hormonal — it's a physical barrier that matches females' aggressive rejection of mates.

Once mating occurs, females quickly become hostile again. Males are driven off immediately, and the external vaginal opening closes again.

Why would this system evolve? Underground life requires: - Constant territorial defense - High aggression to protect food resources - No distractions from the serious business of survival

The ovotestes and vaginal closure ensure females stay focused on survival, opening up only briefly for reproduction.