a very strange case: snow monkey tries to mate with a deer

A male monkey in Japan has been filmed trying to mate with a female deer—likely the first observation of two distantly related species having a nonviolent sexual encounter.

Japanese macaques and sika deer regularly hang around each other on the island of Yakushima. This association has little to do with camaraderie: The deer know that if they stay close to the macaques, they can scarf up any fruits that the macaques drop from the canopy above.

The deer have also been seen eating the monkeys’ feces, and the primates, in turn, have been seen grooming and even riding the deer, says C├ędric Sueur, an animal behaviorist at Hubert Curien Multidisciplinary Institute in France. (See a woodpecker atop a weasel and other animals riding animals.)

These are the interactions wildlife photographer Alexandre Bonnefoy hoped to capture when he visited Yakushima for an upcoming photography book, Saru. But he ended up getting more than he bargained for when he captured a single male macaque mounting two separate female deer.

When Bonnefoy showed the video to Sueur and several other primatologists, the scientists quickly realized nothing like this had ever been seen before on Yakushima—or anywhere, for that matter.

“Heterospecific sexual interaction between non-closely related species is very rare to observe,” says Sueur, senior author of a study published this week in the journal Primates. “This case is only the second one to be reported.”