The orchid bat (Eptesicus serotine) is the most famous disproportionate penis in the animal kingdom. With a seven-fold difference between his erect penis and the female vagina, it’s clear that penetration is impossible. This species, found throughout Europe including the Iberian Peninsula, has no choice but to find another way to mate.
An international team of researchers has discovered that bats use their large penises as an extra arm to push against the female’s tail membrane during mating. This non-penetrative mating behavior resembles the ‘cloacal kiss’ of birds and is the first time it has been documented in a mammal.
Lead researcher Nicolas Fasel from University of Lausanne explains, “We always wondered how these bats with such long penises could mate. We observed that they used their penises like an extra arm to push against the female’s tail membrane and make contact for mating.”
The team accessed the entire scene using images from cameras placed behind a grate at bat habitats in Ukraine and Netherlands. They analyzed 97 mating acts: 93 from Dutch church attics and four from Ukrainian rehabilitation centers. The recordings revealed that bats do not practice penetrative sex and that erectile tissues of the penis enlarged before making contact with the vulva during mating. During mating, males grabbed their mates by neck and pelvis, making probing movements until they made contact with the female’s vulva before staying still in a long embrace for up to 12 hours after copulation. Females appeared moist after copulation, suggesting semen transfer but more research is needed to confirm it.