Sealed Shut Until Mating Season
Mouse lemurs and dwarf lemurs develop a membrane that seals their vaginal opening completely closed outside of breeding season.
Several lemur species have evolved a dramatic solution to controlling when they mate: their vaginas seal completely shut outside of breeding season.
In mouse lemurs, dwarf lemurs, and other strepsirrhine primates, females develop a membrane seal called vaginal closure that covers the vaginal opening during non-mating periods.
How it works: - During the non-breeding season, tissue grows over the vaginal opening - The membrane creates a complete physical barrier to mating - As breeding season approaches, hormonal changes cause the tissue to break down - The vagina opens, signaling the female is ready to mate
This is one of the most extreme examples of seasonal reproductive control in primates.
Why evolve such a system? In Madagascar's harsh environment: - Resources are scarce and unpredictable - Timing reproduction perfectly is crucial for offspring survival - The seal ensures no energy is wasted on off-season mating - Females maintain complete control over their fertility
Mouse lemurs are the world's smallest primates — some species weigh less than 30 grams (about one ounce). Every calorie matters when you're that small.
The vaginal closure membrane is part of a suite of adaptations including torpor (a hibernation-like state) that help these tiny primates survive Madagascar's challenging dry season.