When female chimps become baby killers

On Feb. 3, 2006, six females from an African chimpanzee community attacked a female from outside their group that was holding a 1-week-old infant. Bloodied and screaming, the outsider tried to flee. The attackers, five carrying their own infants, caught her and pounded on her back. Three adult males from the community tried unsuccessfully to break up the assault. After about 10 minutes, the attackers grabbed the outsider’s infant. One of them delivered a fatal bite to the helpless animal’s head and neck.

WILD HOMICIDE. Female chimps, such as this one shown with her infant, sometimes band together in order to attack and kill others’ infants, a new study finds. K. Slocombe

A research team led by Simon W. Townsend of the University of St. Andrews in Scotland observed this incident and collected evidence from two other recent instances of female-led infanticide among wild chimps. Under certain circumstances, it’s not unusual for bands of female chimps to become baby killers, the researchers assert in the May 15 Current Biology.

That conclusion challenges the longstanding view that infanticide in chimps and other primate species mainly involves males trying to jump-start the sexual receptivity of infants’ mothers.

Female-led attacks on others’ infants may stem from an influx of adult females and their offspring into an established group, upsetting residents’ foraging and mating practices, the scientists propose. Since 2001, at least 13 females have immigrated into the Townsend-monitored chimp community, many with dependent children. Because of its relatively low number of adult males, the community has not been able to expand its home range. Immigrants thus challenge resident females’ access to regular food sources and to a limited pool of potential mates.

Bruce Bower

Bruce Bower has written about the behavioral sciences for Science News since 1984. He writes about psychology, anthropology, archaeology and mental health issues.

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