New Scientist

How did the chimpanzee cross the road?

* 14 September 2006
* From New Scientist Print Edition. Subscribe and get 4 free issues.

Cautiously, it would seem. When it comes to crossing roads, chimps seem to have formulated their own version of a highway code. What's more, the time they spend pondering a strategy before crossing depends on how dangerous the road is.

When some monkeys and baboons cross risky terrain, adult males travel at the front of the group to reduce the risk of it being attacked by predators. This had never been recorded in great apes, but now Kimberly Hockings of the University of Stirling in the UK and her team have found that chimps display a similar behaviour when crossing roads that carve through the forests in which they live and forage.

She has found that adult males in the group of 12 chimps she studies in Bossou, Guinea, take up the front and rear position as the group crosses roads in single file, while more vulnerable females and juveniles occupy the less exposed centre of the group. During the 28 crossings she observed, the position of the alpha and other dominant males changed depending on the perceived risks. In some cases, adult males stood guard - lollipop-lady or crossing-guard style - waiting for the group of chimps to make it across (Current Biology, vol 16, p R668).

This suggests they may cooperate to decide on the safest strategy, says Hockings. "Road crossing is just one of chimpanzees' many adaptations to a human-dominated environment," she says, and "may be a sort of culture passed down through generations."

From issue 2569 of New Scientist magazine, 14 September 2006, page 17

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