Sex between monkey and deer may be a new 'behavioural tradition', scientists say

Researchers call for more more studies to discover if relationship is 'short-lived fad' or 'culturally maintained phenomenon'

Sex between a group of monkeys and deer may be a new “behavioural tradition”, scientists studying the creatures have said.

Male Japanese macaques were first filmed earlier this year mounting female sika deer in Minoo, Japan. It was unclear whether this was a case of “misdirected mating”.

However, scientists have suggested the unusual behaviour may well be sexual after adolescent female monkeys and sika stags were also observed copulating.

Publishing their findings in the Archives of Sexual Behavriour journal, researchers hypothesised that there could be several different reasons why the animals are taking part in inter-species sex.

They suggested young female monkeys may be using the interactions as practice for eventual mating with male macaques.

Adolescent females, who are routinely rejected by older males, could also be using the deer as an “outlet for sexual frustration”, they said.

Finally, the report’s authors theorised sex between the two species was the start of a brand new “behavioural tradition”, which could either develop into a “short-lived fad” or a “culturally maintained phenomenon.”

The study said: “The monkey-deer sexual interactions reported here may reflect the early stage development of a new behavioural tradition at Minoo.

“Observational learning and social tolerance towards unusual sexual interactions are likely conducive to the expression, spread, and maintenance of other non-conceptive sexual behaviours in this primate species.

“Monkey-deer sexual interactions had never been noticed at Minoo before 2014. Future observations at this site will indicate whether this group-specific sexual oddity was a short-lived fad or the beginning of a culturally maintained phenomenon.”

The Minoo macaques and deer are not the only animals known to look for sex outside their own species.

Antarctic fur seals have been observed trying to mate with king penguins, while types of bird, cat and dolphin has also been known to carry out the behaviour.

However, while these interactions are usually a case of one an aggressive animal sexually harassing another, scientists believe the deer and macaques have sex consensually.

The report stated: “During the vast majority of heterospecific consortships, adult male deer behaved passively, either standing still or slowly foraging while being recipients of the monkeys’ sexual activities.

“Our preliminary observations suggest that this tolerance on the part of stags may translate into some potential hygienic benefits in the form of allo-grooming by the monkeys. This grooming was specifically directed to body parts that are not easily accessed by the deer.”