Wild Monkeys and Deer Are Now Having Sex With Each Other and Scientists Don't Know Why

A male snow monkey sexually mounting a female sika deer. Alexandre Bonefoy

After video went viral that showed a snow monkey sexually mounting a sika deer, scientists have published a research paper on the behavior.

What they found was that monkeys' predisposition to mount deer, while surprising, was not abnormal. In fact, it's a cultural action, either a fad or an ingrained tradition among the primates.

In research published in the journal Archives of Sexual Behavior, scientists documented repeated attempts by Japanese macaques, also known as snow monkeys, to climb on the backs of deer and thrust their pelvises.

Because of the anatomical differences between the species, videos of the interactions don't show actual sexual penetration. (And don't worry, even if they did actually copulate, monkeys and deer are too far removed genetically to make baby hybrids called "meer" or "donkeys.") Additionally, it was primarily adolescent females that were humping the cervines. Incidentally, both species have mating seasons at the same time.

The scientists are certain that the monkeys' advances toward the deer are sexual in nature, because the actions resemble the actions that the female monkeys make toward male monkeys before they actually mate. Oddly, the female monkeys were primarily observed mounting male bucks. It's unknown whether that's because female deer and juveniles would buck them off, or because the monkeys actually had a sexual preference for stags.

The researchers documented interactions between snow monkeys and their sexual partners. They found that snow monkeys have no preference between sex within their own species or with another. There was no difference in how long the monkeys spent on top of their partner of either species, but they did prefer doggy-style with the deer. (Other positions would prove logistically challenging.)

The deer, for their part, didn't seem to mind.