(AFP) – Jun 18, 2008
LONDON (AFP) — 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 Scottish university has found.
Scientists at St Andrews university studied the copulation calls -- sounds they make during mating -- of female chimpanzees in Uganda to find out more about what they mean.
The Scottish institution's team concluded that female chimps sometimes keep quiet during sex so their female rivals do not find out what they have been up to.
Evolutionary psychologists Simon Townsend and Klaus Zuberbuhler studied chimp behaviour 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 to attract them to have sex.
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.
"Chimpanzee females adjusted their calling behaviour in flexible ways, potentially to avoid aggression from other females and possibly to secure future benefits from the socially important males," the study said.
The research indicated that the social pressures deriving from resource competition acted as an important selective force, shaping the copulation calling behaviour in wild chimps.
"Competition between females can be dangerously high in wild chimpanzees," said Townsend, part of the team.
"Our findings highlight the fact that these females use their copulation calls in highly tactical ways to minimise the risks associated with such competition.
"The female chimps we observed in the wild seemed to be much more concerned with having sex with as many different males as possible, without other females finding out about it, than causing male chimps to fight over them.
"We also found that the calling behaviour of copulating females was unrelated to their fertile period and therefore not linked to the likelihood of conception."
Zuberbuehler added: "Copulation calling may be one potential strategy employed by female chimpanzees to advertise receptivity to high-ranked males, confuse paternity and secure future support from these socially important individuals."
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