Why Biologists Care About A Macaque And Deer Caught On Camera In Rare Interspecies Mating Act – Forbes
An unexpected pair has been caught in flagrante delicto and scientists got it all on tape.
Primate researcher Marie Pelé and colleagues published a surprising note in the journal Primates this week—the second documented case of distantly related species attempting to mate with each other. Most interspecies sexual behavior occurs between closely related species, which is how hybrid species are created, but this instance of a primate attempting to mate with a deer is uncommon indeed.
The one previously documented case definitely raises eyebrows. A young adult male Antarctic fur seal crossed not only species borders but family borders when it attempted to have sex with an adult king penguin on the sub-Antarctic Marion Island. Scientists called the treatment of the penguin by the seal “harassment” as it laid atop the penguin, unable to move. This behavior between fur seals and king penguins has been subsequently observed numerous times, and sadly for the penguin that can’t catch a break, occasionally ends with the bird being killed and eaten at the end of it all.
In this case, Pelé and colleagues had already been observing communities of Japanese macaques on the island of Yakushima in Japan to note cultural differences among the primate groups. Study co-author Alexandre Bonnefoy was out observing and video-taping one November day in 2015 when he caught this somewhat shocking behavior on camera (the slightly not-safe-for-work video can be found here).
The macaque hops on the back of the female sika deer and attempts a sexual act, but as the authors describe, either a morphology or size difference prevents penetration. This male macaque gave it a try twice with two different deer, but penetrated neither. Although, the authors note, “ejaculation seemed to occur as the deer was seen licking the seminal liquid after the mount.”
Besides this untoward act, the Japanese macaque and sika deer typically have a harmonious relationship with each other on Yakushima Island, as the deer often eat fruit the macaques drop from trees and also on occasion, the macaque’s poop.
The researchers are not exactly sure why the macaques would bother with this unproductive behavior. It doesn’t make sense that it is for learning how to have sex or any sort of species confusion. The best idea is one known as the “mate deprivation hypothesis,” where male macaques with little or no access to females need to get their frustrations out elsewhere. They hope understanding why this behavior occurs will clarify the psychology behind zoophilia (also known as humans having a sexual interest in other animals). Clearly, as undeniably popular as the topic is, humans still have a lot more to learn about sex in the animal kingdom.
Shaena Montanari is a paleontologist at the University of Edinburgh. Follow her on Twitter at @DrShaena for the latest natural history and fossil news.