Monkeys of various ranks like to have sex with each other — but only when no one’s looking

Life is tough for male and female macaques monkeys - especially when they're horny. Like many primate species, their sex life is right out there in the open for everyone to see, including alpha males and alpha females who do their darndest to prevent low ranking monkeys from having sex with each other. And indeed, as a recent study by Anne Overduin-de Vries has revealed, monkeys will avoid having sex when troublesome bystanders are around - but things change when no one's looking.

Sexual competition is intense among macaques. Males compete with males, females with other females, and alphas of both sexes try to control things for themselves. Monkeys aren't stupid, of course, so couples intent on doing the nasty have learned to do it privately. But what scientists weren't sure of was whether or not these so-called "sneak copulations" were tactical or opportunistic. In other words, they didn't know if the amourous monkeys were actively trying to deceive the members of the high ranking group, or if they were just chance encounters when competitors were absent.

According to Overduin-de Vries's work, it appears to be the latter. Macaques, as it turns out, simply take advantage of the fact that no one's looking.

To reach this conclusion, Overduin-de Vries and her colleagues observed the sexual dynamics of a group of 27 long-tailed macaques living at the Biomedical Primate Research Centre in the Netherlands. They analyzed which individuals were responsible for breaking-up would-be couples, and how they were related to those members in terms of sex and rank. They also tracked how the monkeys adjusted their requests for sex when potentially harassing bystanders were around. Finally, they studied whether those involved in sneaky sex were being tactical or opportunistic.

What Overduin-de Vries discovered was that both males and females harass copulating couples, and they both disrupt the sexual behavior of their group members. The researchers also discovered that both sexes will refrain from offering sex when there's a potentially disrupting bystander around - regardless of rank. Interestingly, males do it to prevent other males from having sex (male-male competition), and females do the same (female-female competition). Opportunities, it would seem, trump social status.

As for their motivations, the researchers found no evidence of tactical deception. They're simply exploiting the situation, particularly when alpha males are not around.

The entire study was published in Behavioral Ecology and Sociobiology (DOI 10.1007/s00265-012-1430-4). It's not online yet, but we'll post a link once it becomes available.

Image: Gabi Siebenhuehner/Shutterstock.