Chimps reveal mystery of female sex cries

Elephants, lions and humans are all known to do it but it has taken a study of wild chimpanzees to understand why the female of the species calls out loudly whilst having sex.

Scientists refer to it as the "copulation call" and it was thought to be a way of letting other males in the vicinity know that a receptive female is available, increasing Darwinian competition between the chaps.

A female chimp's call during copulation

However, a study of chimps in the Budongo Forest of Uganda has found that females only call out during copulation with a high-status male, but keep quiet when other females are nearby. This suggests that female chimps are using the copulation call as a way of ensuring that they mate with as many males as possible without other females knowing about it. The study found females keep quiet when other females are around but call out as a tactical ploy to enlist the protection of high-status males against aggressive high-status females, scientists said yesterday.

Simon Townsend of St Andrews University, Fife, said: "Competition between females can be dangerously high in wild chimpanzees. Our findings highlight the fact that these females use their copulation calls to minimise the risks associated with such competition," Dr Townsend said.

"We found the calling behaviour of copulating females was unrelated to their fertile period and not linked to the likelihood of conception. Females called more with high-ranking males, but suppressed calls if high-ranking females were nearby." The study is published in the online journal Public Library of Science.