* 17:11 13 October 2008

    * NewScientist.com news service

    * Ewen Callaway

Don't be fooled by their reputation for altruism and free love – bonobos hunt and kill monkeys just like their more vicious chimpanzees cousins, according to new research.

"Bonobos are merciless," says Gottfried Hohmann, a behavioural ecologist at Max-Planck Institute for Evolutionary Anthropology in Leipzig, Germany. He witnessed several monkey hunts among bonobos living in the Democratic Republic of Congo, and says, "they catch it and start eating it. They don't bother to kill it".

Yet unlike chimps, bonobos live in female-centred societies where sex, not aggression, settles differences and enforces social order.

Hunt strategies

Fruit makes up much of their diet, but the primates aren't herbivores. Small ungulates called forest antelopes, or duikers, often fall prey to bonobos.

These hunts tend to be fairly simple, with a single bonobo cornering a duiker then quickly feasting on the still-living animal as more apes hurried to the scene. Hohmann says he has witnessed a duiker "still vocally blurting as the bonobos opened the stomach and intestines."

In three successful monkey hunts that Hohmann and Max Planck colleague Martin Surbeck witnessed in the Salonga National Park, bonobos took a more cautious team approach once they spotted monkeys in a nearby tree.

"They fall silent, and they try to go underneath the monkey group, of course remaining undetected," he says. "Then it's a sudden rush. Two, three, four bonobos climb up into the trees and try to catch a monkey."”

'Still peaceful'

Males and females hunt together, and females tended to share their spoils, which included the young of two species of monkeys.

The discovery casts doubt on claims that social aggression and hunting go hand in hand, Hohmann says. Some anthropologists suggest that in the million or so years that separate bonobos from chimps, bonobos lost their appetite for violence.

"What a great discovery," says Frans de Waal, a primatologist at Emory University in Atlanta.

"The chimpanzee literature sometimes depicts bonobos as the less interesting, less human-like, less cultured, less cooperative branch of the family tree," he says, "and I am not sure this characterisation can be maintained for much longer with this kind of observation coming out."

However, de Waal notes that predation and aggression are distinct behaviours, pointing out aggressive herbivores such as bison and sociable carnivores such as lionesses as examples. "For me, this finding does very little to change the idea of bonobos as relatively peaceful primates."

Journal reference: Current Biology