Wild monkey filmed mounting deer and trying to have sex with it

She’s just not that into you

Alexandre Bonnefoy – Éditions Issekinicho

By Andy Coghlan

Oh deer! A male Japanese macaque monkey has been caught in the act of trying to mate with two Sika deer by leaping on their backs, rodeo-style.

Captured in November 2015 by researchers monitoring the macaque monkeys – made famous by videos of them bathing in hot springs – the footage shows that both attempts at copulation were unsuccessful, the only genital contact being with the deer’s back (see video below).

The monkey’s first attempt met with no resistance from the deer. But when he tried it with a second deer, she did her best to shake him off. Afterwards, he also appeared to try and “guard” the deer against rival monkeys.

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Such observations are rare but not unheard of.

The birds and the bees

In the 1990s, forest rangers reported orphan elephants attempting to mate with rhinos, and in 2008 footage was taken of a chimpanzee attempting to mate with a frog. In 2014, there were reports of sea otters attempting to mate with cormorants. Also in 2014, an Antarctic fur seal was observed attempting to mate with king penguins, some of which he subsequently ate.

In this latest example, on Yakushima Island south of Japan, the perpetrator was a young male macaque – one of the more peripheral members of a larger group. This means he was probably frustrated by not having a mate.

The events coincided with the monkeys’ mating season, and the researchers, led by Marie Pelé of the University of Strasbourg in France, think the hormonal surge prompted the behaviour.

Pelé and her colleagues say that the habitats of the monkeys and deer overlap, and the deer often benefit when the monkeys shake down food from trees, snaffling the spoils and sometimes consuming the monkeys’ faeces.

The deer also seem to tolerate periodic attempts by the monkeys to ride on their backs, which may explain the mating attempts. “It could be a manifestation of the known play behaviour between Japanese macaques and the deer they are known to sometimes ride,” she says.

“Sexual interaction between non-closely-related species is very rare to observe,” says team member Sueur Cédric. Determining the causes of this is difficult, but whatever it may be, this observation might help us to understand evolution of such unusual behaviour.

“It would be interesting to continue to observe these Japanese macaque male groups in Yakushima as this species is known to display cultural behaviours and social learning,” he says. “As a consequence of not having access to females, these peripheral males could socially learn to have sexual interaction with Sika deer in order to decrease their sexual frustration.”

It’s not clear what, if any, impact this behaviour has on the monkeys’ survival and reproduction odds. “If they can access macaque females during the following years, their fitness should not be affected in the long-term, only in the short-term due to loss of energy, gametes and time.”

Journal reference: Primates, DOI: 10.1007/s10329-016-0593-4

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