Bonobos are what you’d call sexually dimorphic, meaning the females and the males are noticeably different. The males are larger and stronger compared to the females, and yet they’re the ones that will sit and wait in the trees while the females have their fill of a fresh kill. Females also decide who they mate with, and don’t suffer any unwelcome advances.
It’s a disparity between apparent physical strength and social standing that Harvard University’s Martin Surbeck describes as “totally bizarre for an animal like a bonobo.” The males have all the physical ingredients to be the dominant sex, and yet smaller females often come out on top.
Now, new research has found the first empirical evidence to explain why this might be. According to its findings, females are able to maintain dominance by forming alliances with other females. They team up in groups coined “coalitions”, which in 85 percent of observations went around targeting males and forcing them into submission. This shaped the group’s dominance hierarchy, creating a mechanism through which females could behaviorally elevate their status.
“To our knowledge, this is the first evidence that female solidarity can invert the male-biased power structure that is typical of many mammal societies,” said Surbeck in a release, who runs the Kokolopori bonobo research station and is the study’s first author. “It’s exciting to find that females can actively elevate their social status by supporting each other.”
The findings follow an impressive three decades of data collection, encompassing six wild bonobo communities across the Democratic Republic of the Congo. It adds up to 1,786 conflicts between male and female bonobos, 1,099 of which were won by females. Factors contributing to fighting success included strength, having back-up, and resources that other bonobos didn’t have.
Within seconds of an inciting event, such as a male attempting to injure a juvenile, females within a coalition would scream so loud it had the human observers covering their ears. The coalitions then pursue the male, attacking and sometimes killing them in a way that likely leaves a lasting impression on the rest of the community.
This seems particularly surprising among bonobos as adult females within a community are all unrelated to one another because they have to leave the group they’re born into before they hit puberty. So, to find these females forming such deep bonds and cooperating to such a high degree is unexpected in the context that they’re not kin.
There remain many questions about how and why these coalitions form, but the researchers highlight that the discovery also raises interesting questions about our own evolution.
“I’m still puzzled why, of all animals, bonobos were the ones to form female alliances,” added Barbara Fruth of the Max Planck Institute of Animal Behavior, who has led the LuiKotale bonobo research station for 30 years. “We might never know, but it gives me a glimmer of hope that females of our closest living relatives, in our evolutionary line, teamed up to take the reins of power alongside males.”
The study is published in the journal Communications Biology.
Source Link: Female Bonobos Can Elevate Their Status By Teaming Up To Gain Power Over Males
