Chimpanzees: 'New Girl' Forms Stronger Female Bonds

When it comes to chimpanzees, it seems that the "new girl" may have the upper hand in former stronger female bonds, new research says.

Unlike most primates, female chimps are loners compared to males, spending about half their time either alone or with dependent kids.

"Chimpanzee females' more solitary existence isn't that surprising given their dispersal patterns," researcher Anne Pusey, a professor of evolutionary anthropology at Duke Unviersity, said in a statement. Meaning, while males stay with the group they were born into their entire lives, many females choose to leave their families and join new groups.

But despite their reputation for being aloof, recent studies suggest that some pairs of female chimps hang out together more than others. Now, as the new girl in the group, you would think that it would be hard to make friends. However, the Duke team finds that low-ranking "new girl" chimps actively seek out other gal pals with similar status, thereby forming strong social bonds.

In order to figure this out, and rule out the possibility that these chimps were merely crossing paths by chance, Pusey and colleagues analyzed 38 years' worth of daily records for 53 adult females in Gombe National Park, a 13.5-square-mile park in western Tanzania.

Over the years, the females were spotted in more than 600 female-female pairs. For each pair, the researchers measured how much their ranges overlapped, how much time they spent together, and how often they groomed each other - a symbol of friendship and bonding.

Based on their findings, it turns out that some female-female relationships are tighter than others.

Not surprisingly, mothers, daughters and sisters formed the strongest bonds. However, among unrelated females - which made up more than 95 percent of the twosomes they studied - low-ranking females were more likely to seek each other out than females from other social ranks.

"It doesn't necessarily mean that they like each other," Foerster was quick to add. "The lowest-ranking females are the newest to arrive. When a female migrates into a new group, she starts at the bottom of the social ladder. It may be that they're not really that into each other, but that they need to tolerate being in the same space."

Also, it could be that low-ranking females team up for support against harassment from higher-ranking females, or as a means to compete for food or spot predators.

Further study is needed to determine whether the "new girls" are true buddies, friends of convenience or merely acquaintances.

The results were published in the journal Animal Behaviour.

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