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.
The footage was captured in November 2015 by researchers monitoring the macaque monkeys. In the footage, the animals are seen unsuccessfully trying to have s*x, the only genital contact being with the deer’s back.
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, NewScientist reports.
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.
“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.”
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