Bat With a Disproportionately Large Penis Is the First Mammal to Reproduce Without Penetration

Video recordings have revealed the astonishing mating method of serotine bats, making them the first known mammals to reproduce without penetration.

Unusual Mating

Fascinating creatures, bats are known for their remarkable longevity despite their small size (some species are believed to live over 40 years) and the surprising aspects of their sexuality, with females capable of storing the male’s sperm in their uterus for months and previously observed engaging in fellatio.

Published in the journal Current Biology, research led by Nicolas Fasel of the University of Lausanne and his colleagues unveiled the unique mode of reproduction of the serotine bat (Eptesicus serotinus), a species widespread in forests across Europe and Asia.

By examining footage of individuals roosting in the attic of a Dutch church and at a Ukrainian rehabilitation center, the team found that the males possessed a disproportionately large genital organ, featuring a heart-shaped tip. Overall, its erect length measured about a quarter of the males’ body length and seven times the length of the females’ vagina.

An analysis of 97 filmed matings of E. serotinus showed that these interactions did not involve penetration. The males simply used their erect organ as an arm to part the protective membrane surrounding the females’ vulva. Commonly observed in birds, this mode of reproduction (known in birds as the “cloacal kiss”) had never before been documented in a mammal.

Embraces that can last for more than 12 hours

Once the tip of the male’s penis is pressed firmly against the partner’s vulva, the two bats remain motionless in a protracted embrace that can endure for over 12 hours.

According to the study authors, it is likely that other bat species reproduce in this manner, and that the E. serotinus females also store sperm from different males in their long cervix.

Not surprisingly, this is not the only unusual reproductive behavior in the animal kingdom. Females of a Brazilian insect species are notably known for inserting their “penis” into the males’ “vagina.”