Chimps' 'girl talk' uses more negative gestures
Female chimpanzees are more "negative" when communicating with other females, research has found.
The study analysed the different gesturing strategies used by a group of females at Chester Zoo.
In female-female interactions, the chimps used more aggressive signals and "apologised" less often with gestures of reassurance.
But they employed a more positive strategy around males, with more expressions of greeting and submission.
"When communicating with males, females sort of 'suck up' to them," said PhD student Nicole Scott from the University of Minnesota, Minneapolis, US, whose findings are published in the American Journal of Primatology.
To carry out the research, Ms Scott video-recorded the behaviour of 17 females and five males in a group of chimps at Chester Zoo, UK.
"I defined gesture as an expressive movement of the limbs or head and body postures produced intentionally," she told BBC Nature.
Examination of overall behaviour in males and females showed no differences in the repertoire of gestures the animals used. But differences in communication appeared when individual interactions were analysed.
While females in the group adopted a different gesture strategy depending on the sex of a partner, the males did not.
Ms Scott suggests this indicates that female chimpanzees are more sensitive to the sex of their partner than males, and cater their gesture use accordingly.
According to the biologist, different "social pressures" on the sexes could explain the difference in communication strategies.
For example, males might have more positive relationships with other males because of the importance of male-male alliances and maintaining high social rank in a group.
But there may be less focus on female chimpanzees maintaining multiple, positive relationships with other females, and instead more pressure on them to form positive relationships with males.Parallel lives
Ms Scott suggests the complex social behaviour seen in chimps, and highlighted in her study, may hint at our own actions:
"To speak anthropomorphically, I can certainly see some parallels in my own life: women are generally more aggressive and competitive with each other... [and] men do not change their behaviour outside the context of social rank," she said, referring to studies of gesture differences in humans.
"Perhaps we inherited these traits from our ancestors, traits which were adaptive for their social pressures, but I'll leave that argument for the anthropologists."
She added that her analysis of female aggression could be controversial because "there is a belief in the field that males are more aggressive than females."
"Some researchers likely will have trouble accepting my results since I show that females are also aggressive," she said.
"It's not that they are more aggressive, just different from males in their use of aggression."