Sex between two males is extremely common in wild macaque monkeys

Sex between two males is extremely common in wild macaque monkeys

A pair of male macaques in Cayo Santiago, Puerto Rico

Chloe Coxshall

Gay behaviour seems to be widespread amongst male macaque monkeys within the wild and the trait could also be no less than partially handed down in genes from father to son. Such behaviour could present evolutionary benefits stemming from sturdy male alliances, says Vincent Savolainen at Imperial School London.

“They type bonds, and so they assist one another in a struggle,” says Savolainen. “After which the concept is that in the event that they do that, then they may even have entry to extra females and, in impact, have extra infants.”

Occasional same-sex touching has been noticed in quite a few animal species, however it’s usually regarded as uncommon. Savolainen has usually questioned a preferred perception referred to as the “Darwinian paradox of homosexuality”, which suggests that as a result of gay behaviour doesn’t result in replica, it has no profit and any genes that advertise must be eradicated by pure choice.

To research homosexuality in different primates, Savolainen and his colleagues determined to review a colony of 1700 wild rhesus macaques (Macaca mulatta) on the Puerto Rican island of Cayo Santiago. The colony has been adopted by scientists day by day for the previous 67 years and DNA-tested for paternity since 1992. In 2017, 2019 and 2020, the crew noticed 236 of the colony’s males, which belonged to 2 social teams, for 7 hours a day over 72 days.

The researchers discovered that 72 per cent of the males mounted different males, whereas solely 46 per cent have been noticed mounting females. As a result of they didn’t need to intrude with the animals, the scientists solely visually noticed the animals from a distance and couldn’t all the time see precise penetration, though they generally noticed sperm plugs – which type after ejaculation – within the anuses of some males.

In 16.5 per cent of circumstances of same-sex mounting, the 2 males fought collectively towards different monkeys earlier than partaking in intercourse.

Similar-sex mounting turned much less frequent with age, nonetheless, offering assist for a standard speculation that it might function “follow” for future reproductive exercise, says Savolainen.

The household historical past of the monkeys revealed that same-sex mounting was 6.4 per cent heritable – that means genetics could play a small position along with different components, says Savolainen. The behaviour appeared to don’t have any destructive penalties on reproductive success, he provides. Quite the opposite, males partaking in same-sex mounting tended to have barely extra offspring.

The males’ mounting exercise is unlikely to be merely a present of dominance, says Savolainen, because the monkeys have been mounting higher-ranking males almost half the time. “They’ve erections generally; they’ve penetration generally, and so they even have ejaculation generally,” he says. “So I feel it’s sufficient to name it intercourse, and never dominance.”

Whereas researchers can’t decide what animals are considering as they choose sexual companions, the research helps to dispel the notion that same-sex behaviour is by some means unnatural, says Jon Richardson on the College of Minnesota, who wasn’t concerned within the research. “I’m hopeful that we actually are beginning to transfer away from the antiquated concept that [homosexuality] in animals is an evolutionary paradox or aberration.”


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