Aggressive Male Chimps May Father More Children by Bullying Females

When it comes to natural selection, the bullies win out. Scientists have found that chimpanzee males that treat females aggressively father more offspring over time. The findings reveal a bit more about how sexual coercion via long-term intimidation may actually be an adaptive strategy in chimpanzee society.

"These results seem to suggest that males are selected to be aggressive toward females to increase their paternity success, which explains why male-female aggression is observed in some many chimpanzee populations," said Joseph Felblum, one of the researchers, in a news release.

Male chimps are known to be surprisingly aggressive toward their female group mates. While previous research found evidence both for and against the presence of sexual coercion in wild chimps, scientists decided to get to the bottom of the matter.

The scientists examined a chimpanzee community living in Tanzania's Gombe National Park. More specifically, they looked at the effect of male aggression toward females both when the females were sexually receptive and when they weren't.

In the end, the researchers found that male aggression during a time when a female was sexually receptive led to more frequent mating, but not greater paternity success. However, high-ranking males that showed aggression toward females when the females weren't sexually receptive had more offspring in the long-term.

Currently, the researchers are interesting in finding out whether some males may also be successful in paternity with gentler methods; for example, they may spend more time grooming females. That said, the scientists say that the findings in chimps probably don't have much to tell us about human society

"The glaring difference between chimpanzee and human mating behavior is that in chimpanzees females mate promiscuously with most male group mates during most cycles, while human females do not," said Feldblum. "Thus, the system that favors male coercion in chimpanzees is not present in humans to favor this behavior."

The findings are published in the journal Current Biology.