K. HOCKINGS ET AL., CURRENT BIOLOGY 16, 688 (2006)

Group dynamics.
On dangerous road crossings, male chimps take the lead and rear, while females and youngsters are protected in the middle.

Male Chimpanzees Show a Caring Side

Male chimpanzees, long considered very aggressive members of the great ape family, may have a caring side after all. A study conducted in Guinea reveals that high-ranking male chimps appear to adopt a protective role to get their group across big streets safely.

Researchers know a lot about how monkeys travel in packs to protect the clan. Males often lead the way toward watering holes that may harbor predators, for example, and they bring up the rear on the way out. But not much is known about how their great ape cousins protect their gang from dangers. Although gorillas have a soft side--they'll care for orphans--adult male chimps will kill baby chimps. Can chimps put aside their aggression for the safety of the clan when it's on the move?

To find out, psychologist James Anderson of the University of Stirling in the U.K. and colleagues traveled to Bossou, Guinea, and watched how 12 chimps, navigating from the forest to their foraging grounds, crossed two roads. One road is narrow and used primarily by pedestrians; the other is four times wider and carries trucks and other vehicles. The researchers found that the animals waited about half a minute before crossing the smaller road, while taking an average of 6 minutes before braving the big one. The authors argue that this represents a flexible response to different amounts of risk.

Particularly interesting to Anderson's team was the behavior of the high-ranking males. On the more dangerous crossing, the males traveled at the front and back of the group. This allowed females and their young to take the safer middle spots, they report in the 6 September issue of Current Biology.

While not surprised that chimps can assess risk and plan their behavior around it, social behavioralist Frans de Waal of the Yerkes National Primate Research Center at Emory University in Atlanta, Georgia, notes that "their aggressiveness is hyped everywhere. The image of [male] chimp as protector is an interesting new angle." But he adds that this behavior might be unique to this group of chimpanzees. Many chimp communities are dispersed across large areas, whereas the Bossou colony lives in a small forest, making it "very cohesive."

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