Science : Watch out, bands of marauding chimps are about

 作者:令狐磁     |      日期:2019-02-27 06:11:04
By Meg Gordon THE adage “safety in numbers” is especially true if your companions are more alert to predators than you are. In the dense rainforests of the Tai National Park in Côte d’Ivoire, red colobus monkeys mingle with diana monkeys when chimpanzees are hunting in their neighbourhood for just this reason, according to scientists in Germany. Ronald Noë and Redouan Bshary of the Max Plank Institute for Behavioural Physiology in Starnberg, Germany have been studying the two species since 1991. They found that when chimpanzee hunting parties entered their territory, the red colobus joined forces with the diana. Behavioural ecologists have argued for years over why different primate species sometimes group together. The most popular theory is that joining groups makes it easier to search for food. But although red colobus and diana monkeys share the same territory, they forage for food separately. Groups of male chimpanzees hunt most frequently during the rainy season, from September to November, which is when the two species of monkey tend to pair up. By broadcasting sounds of various predators over loudspeakers, the researchers worked out that the chimps were the trigger. They tested the snarls of leopards, the purr of a diesel generator and other noises, but only recordings of chimpanzees sent them scurrying for their diana companions. The researchers believe red colobus monkeys are better protected when they stick with the diana. The diana are quick to detect marauding bands of chimps, calling loudly to one another and scampering for cover in the tops of high trees: they are small and hardly move the branches of the trees in which they hide. But the relationship could be mutually beneficial, because the red colobus provide extra targets for predators such as leopards. The findings “provide the first direct evidence that different species form groups solely to save themselves from predators”, says Bshary. The research appears in the Proceedings of the Royal Society B (vol 246,