Female Chimps Keep Sex Lives Secret

June 18, 2008 -- Female chimpanzees are hungry for sex with as many males as possible, and keep their mouths shut about it to boost their chances of luring the top chimps, a British university said Wednesday.

Scientists at the University of St Andrews studied the copulation calls -- sounds sometimes made during mating -- of female chimpanzees in Uganda to find out more about what they mean.

The team concluded that that female chimps sometimes keep quiet during sex so their female rivals don't know what they've been up to.

Evolutionary psychologists Simon Townsend and Klaus Zuberbuhler studied chimp behavior in Uganda's Budongo Forest over 16 months.

The team established that female chimpanzees hid their sexual activity when high-ranking females were nearby, perhaps in a bid to reduce competition for good quality males.

This could prevent higher-ranking female chimpanzees from turning on them.

They also found the females produced more copulation calls when high-ranking males were around, presumably to attract them.

The scientists believe that having sex with several males causes confusion among the male chimpanzees as to which one sired the offspring.

The males are therefore less likely to kill any babies that might be theirs.

The study found no evidence that males were competing to have sex with females after they produced copulation calls, and no link between a female's fertility and her use of the calls.