Yes, that’s a monkey living in Japanese forest grinding on top of a deer

AFTER spending a few months observing macaque monkeys living in a Japanese forest, a group of scientists found a pattern of behaviour they described as both “unusual” and “intriguing.”

Adolescent female macaques climbed on top of a sika deer and crouched. Then, they moved their pelvises as if thrusting or grinding. They squeaked sexual sounds. They also bit, sniffed and pulled on the deer’s antlers.

The deer, meanwhile, stood nonchalantly and continued foraging for food.

When the deer walked away, the female monkeys “often displayed sexually motivated tantrums which consist of crouching on the ground, body spasms and screaming, while gazing at the deer,” the scientists wrote in a peerreviewed study published this week in the Archives of Sexual Behaviour.

Scientists found that the interactions, documented in the Meiji Memorial Forest of Minoo Quasi-National Park on the outskirts of the city of Minoo in central Japan, are “sexual in nature” – at least for the monkeys. Japanese macaques are known to ride deer for play or to move from one place to another, but adolescent females appear to have taken this playful interaction a step further. Why they do so remains unclear, but scientists have a few theories. “The monkey- deer sexual interactions reported in our paper may reflect the early stage development of a new behavioural tradition at Minoo,” Noelle Gunst, co-author of the study and a psychology professor at the University of Lethbridge in Canada, told the Guardian.

Whether this is a “short-lived fad” or the beginning of a “cultural phenomenon” also is hard to tell without further research, the authors wrote.

Scientists observed a total of 170 male and female Japanese macaques. Eighteen were adolescent females ages three to four. Over the course of several weeks, scientists observed only adolescent females engaging in sexual activities – with one another and with sika deer. Specifically, adolescent female macaques initiated sexual interaction with a sika deer 258 times. Of these, 13 sexual interactions initiated by five macaques were considered successful. That is, they had a “temporary, but exclusive, sexual association” with the deer. Almost all of the successful interactions involved an adult male deer or a stag, which seemed to passively oblige. Adolescent male and adult female deer, meanwhile, largely avoided the persistent primates.

In five instances, adolescent female macaques intruded on a fellow female’s sexual interaction with a deer and successfully displaced the original “mounter,” the authors wrote. Scientists believe that the stags’ tolerance was mainly driven by nothing more than potential hygienic benefits. While sitting on top of the stags, the monkeys groomed their backs and head.

The authors have a few possible explanations as to why adolescent female macaques engage in such behaviour.

Like humans, adolescent female macaques go through a period in which they begin to develop sexual behaviours. It’s likely that these interactions with deer mates was their way of practising and developing their sexual behaviours, the authors wrote. — WP-Bloomberg