The oversized genitalia of the orchard bat, Eptesicus serotine, is a topic of fascination for researchers worldwide. The species has a disproportionate penis that is seven times longer than the female vagina and has a heart-shaped head that is seven times wider than the vaginal opening. This makes penetration impossible after erection, leading the bats to engage in non-penetrative sex.

Recently, an international team of scientists discovered that bats use their large penises as an extra arm to push against the female’s tail membrane during mating. This behavior resembles the ‘cloacal kiss’ of birds and is the first time non-penetrative sex has been documented in a mammal. The researchers observed 97 mating acts, recording them with cameras placed behind a grate that the bats could climb onto. Some videos were obtained at a bat rehabilitation center in Ukraine and others from a citizen scientist who filmed a garden bat for hours in an attic in the Netherlands.

The recordings revealed that bats do not practice penetrative sex. Instead, male bats grab their mates by the back of the neck and move their pelvises (and fully erect penises) in a probing fashion until they made contact with the female’s vulva. Then they stay still in a long embrace. On average, these interactions lasted less than 53 minutes, but the longest event lasted 12.7 hours. The researchers also noted that females’ abdomens appeared moist after copulation, suggesting sperm transfer occurred during supposed mating events.

Further research on penis morphology and mating behavior will be conducted by this team of scientists to understand more about this unusual sexual behavior in bats.

The discovery of non-penetrative sex behavior among bats raises questions about how other species might have evolved to avoid sexual intercourse altogether or rely on alternative methods of reproduction.

This fascinating study sheds light on one aspect of animal biology that we may never fully understand: why some animals have disproportionate genitalia or engage in unusual sexual behaviors.

Overall, this discovery adds another layer to our understanding of animal biology and opens up new avenues for research into animal sexuality and reproduction.

As we continue to explore these topics further, we can only imagine what other surprises await us in the world of animal biology and behavior!