Male bats perform oral sex on females, apparently to make sex last longer, researchers say.
These findings, the first discovery of male-to-female oral sex in bats, match prior studies revealing that female bats perform fellatio, or oral sex, on male bats.
Scientists analyzed a colony of about 420 Indian flying foxes (Pteropus giganteus) roosting in a single fig tree in southern India, near the village of Nallachampatti. This fruit-eating bat is one of the largest bats in the world.
Over the course of more than 13 months, using binoculars and a video camera, researchers witnessed 57 cases of sex ― oral and intercourse ― usually in the morning.
"Apart from humans, bats also exhibit oral sex as a courtship behavior," said Ganapathy Marimuthu, a bat researcher at Madurai Kamaraj University in India.
Initially, males groomed their penises to go erect before approaching females. When they gently touched females with their wings, females typically moved away, and males followed. [See Video of Bats Having Oral Sex]
When the females stopped moving, the males started licking the females’ vaginas ― the act known as cunnilingus. This foreplay may help arouse and lubricate females, the researchers said.
Each case of cunnilingus typically lasted about 50 seconds. The males then mounted the females for 10 to 20 seconds, and then went back to cunnilingus for 94 to 188 seconds.
The researchers found that the longer the stints of cunnilingus before mating, the more copulation was prolonged.
"It is possible that prolonged copulation enables the mobility of sperm," Marimuthu told LiveScience. "Such mobility of sperm increases the chances of conception."
The scientists also noted that males might perform cunnilingus on females in order to clean off competitors’ sperm. Doing so could help ensure their sperm, and not their rivals', impregnates the females.
"In this context, cunnilingus would be maladaptive after mating, as there is a risk of removing the male’s own sperm," the researchers wrote. "Observation at close range is needed to find out whether the male’s tongue enters the vagina or not."
The bat species found to perform male-to-female and female-to-male oral sex were fruit bats. Oral sex may occur in other species of fruit bats as well, Marimuthu suggested.
Marimuthu and Jayabalan Maruthupandian, also of Madurai Kamaraj University, detailed their findings online March 28 the journal PLOS ONE.
Sign up for the Live Science daily newsletter now
Get the world’s most fascinating discoveries delivered straight to your inbox.