Monkeys have been observed having sex with deer in what scientists believe could be a new behavioural tradition.
Researchers first spotted a male Japanese macaque and female sika deer interacting earlier this year and they are now convinced the behaviour is sexual after watching adolescent females and stags at Minoo, Japan.
Dr Noëlle Gunst-Leca, co-author of the study from the University of Lethbridge in Canada said: ‘The monkey-deer sexual interactions reported in our paper may reflect the early stage development of a new behavioural tradition at Minoo.’
Monkeys have been observed having sex with deer in what scientists believe could be a new behavioural tradition
A male monkey and female sika deer were spotted interacting this year and scientists are now convinced the behaviour is sexual after watching adolescent females and stags in Japan
Sexual interactions between closely related species uncommon but not unheard of and have been observed in a wide range of animals such as fish and baboons, according to the Guardian.
But the only other known instance of it occurring between distant species is the sexual assault of king penguins by Antarctic fur seals.
Researchers filmed the male Japanese macaque, or snow monkey, mounting a female Sika deer on Yakushima island in southern Japan but initially scientists were not sure what was happening.
However in a new study published by the Archives of Sexual Behaviour scientists described their method of figuring out of the monkeys’ antics were sexually motivated.
They travelled to Minoo near Osaka and observed only female snow monkeys mounting deer.
They then compared the interactions to sexual ones between adolescent female monkeys, which is a well known practice.
Scientists believe the behaviour may spread among the monkeys and speculated the female monkeys may have developed a taste for the genital stimulation
During the study, the adolescent females were not observed mounting adult male monkeys.
The team recorded 12 successful sexual interactions between monkeys, involving six adolescent females, between November 2012 and January 2013.
And they recorded a total of 13 successful interactions of what appeared to be of a sexual nature between November 2014 and January 2015.
These involved five female snow monkeys.
When scientists analysed the encounters they could spot no clear difference between the adolescent female snow monkeys and other females or deer on their sexual behaviour.
This includes how often they sought attention, mounted a partner, how long they spent mounted and even their orientation.
It remains unclear why the snow monkeys engage in sexual interactions with deer, but scientists believe they could be practicing for sex with other monkeys
But, unexpectedly pelvic thrusting was more common when the monkey’s partner was a deer.
The team believe the behaviour could be the start of a new trend, saying female snow monkeys could spot others on the backs of deer and try to replace them.
The monkey-deer interactions may be the beginning of a future relationship, they added.
It remains unclear why the snow monkeys engage in sexual interactions with deer, but scientists believe they could be practicing for sex with other monkeys or they could have been rejected by males, leaving them with no sexual partner.
It could also be a safer way to engage in sex by avoiding aggressive male monkeys, scientists said.
Or the monkeys could be looking for genital stimulation.