Macaques in Japan do not stop trying to have sex with deer, and researchers are bewildered.

This year began strong when it comes to the animal world. The researchers captured a video where a male Japanese male macaque tried to have sex (unsuccessfully) with a Sika deer in Japan. They have now registered female macaques with male deer. Hey, what's going on?

In addition, the latter "games" or sexual interactions occurred in a completely different group of animals in another part of the country. Until now, it has been known that Japanese macaques cohabit with Sika deer, as the latter are attracted by food scraps discarded by monkeys on the forest floor.

In fact, the researchers themselves had seen monkeys grooming deer and even riding them, but never this type of sex play. It was thought that the video captured a few months ago with the male macaco might be due to some kind of sexual "frustration" of the animal and that it tried to get even with the deer.

The fact is that it was difficult to judge what might be going on between species with a single example, so the primatologists at Lethbridge University in Canada decided to collect more data from the groups they were observing in Minoo, central Japan. It was known that female adolescent macaques have similar desires: they routinely interact with male and female monkeys, soliciting sex and even riding them.

However, after seeing adolescent females riding male deer in the vicinity, the team decided to compare these two behaviors to see if the interactions really had anything to do with sexuality. As described in the work you've just published:

This is the first quantitative study of hetero-specific sexual behavior between a non-human primate and a non-human non-human species.

After counting a total of 67 "attempts" between two female monkeys and 258 "attempts" between female and deer monkeys, they identified 25 "successful" interactions, defined by three or more attempts over a 10-minute period. Twelve occurred among monkeys, and the other thirteen were links between monkeys. The games lasted from a few minutes to two hours.

In most cases, the deer didn't seem to care at all: they stood still and even kept eating, and only a few stood up to evict the macaques from their backs. The following video shows interactions recorded during the study. Everything seems more or less innocent, while the monkeys move on the deer, who seem bored.

After analyzing the behaviors, the team concluded that there was no significant difference between mono-mono or mono-ciervo interactions, so, indeed, and although it sounds strange, what is observed appears to be macaques having a "moment" with deer.

At this point, the researchers asked themselves the big question, why? The team hypothesizes that there could be several reasons: teens may practice their sexual movements before they engage in real "trying" with their species, or perhaps it is a way to relieve sexual tension, as they may not be able to get a partner from their own species.

As such, the team believes it could be due to the hormones of adolescence, as females have a taste for genital stimulation and choose to participate in it with deer they know are not a threat, unlike, for example, other adult monkeys of their potentially aggressive species.

That said, they are hypotheses. The only thing science is clear to science at the moment is that some female and male macaques are trying to have sex with deer, a species not even remotely close to theirs.

Seen on: National Geographic