Female Chimps May Bond More Strongly with Other Females When Low-Ranked

Low-ranking, female chimps may bond more strongly with other females than with males. Scientists have found that "new girls" will seek out other female chimps with similar status.

Unlike most primates, female chimps are loners compared to males. In fact, they spend about half their time alone or with dependent offspring. Yet this loner lifestyle isn't surprising consider their dispersal patterns; chimps stay with the group they were born into their entire lives, forging strong social bonds with other males. Many females, though, leave their families behind and strike out on their own to join new groups.

While females are usually solitary, though, the researchers found evidence that they may form strong social bonds with low-ranking females. The researchers analyzed 38 years' worth of daily records for 53 adult females in Gombe National Park in western Tanzania.

Over the decades, 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.

So what did they find? Mothers, daughters and sisters formed the strongest bonds. But among the 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," said Steffen Foerster, one of the researchers, in a news release. "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."

The findings reveal a bit more about chimp society. Understanding these social networks is important for improving the health of chimps in captivity in addition to conservation efforts.

The findings are published in the journal Animal Behavior.

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