Interesting short piece about a recent publication by Richard Wrangham and his research group in Uganda. It appears that young females - solely in this chimp community (it has never been noticed anywhere else) - carry sticks as young human females carry dolls. The practice ceases when they become pregnant for the first time. Here is the bounce, courtesy of Cell Press and World Science.
"Young chimpanzees, and most often females, at a national park in Uganda some times play with sticks in a way reminiscent of the way children play with dolls, scientists are reporting.
The practice might turn out to be the first case among animals “of a tradition maintained just among the young, like nursery rhymes and some games in human children,” said Harvard University researcher Rich ard Wrangham. “This would suggest that chimpanzee behavioral traditions are even more like those in humans than previously thought.”
But he added that the stick-playing is relatively rare, and undocumented in other chimp communities. The findings, by Wrangham and colleagues, are published in the Dec. 21 issue of the research journal Current Biology.
This is “the first evidence of an animal species in the wild in which object play differs between males and females,” said Wrangham. The gender difference in chimps’ apparent “doll” play also fits the pattern seen across human cultures, he added—suggesting it stems from “biological predilections” rather than socialization.
Although both young male and female chimps play with sticks, females do so more often, and they occasionally treat them like mother chimps tending their infants, the researchers said. Earlier studies of captive monkeys had also suggested a biological influence on toy choice, accord ing to Wrangham and colleagues: when young monkeys are offered sex-stereo typed human toys, females gravitate toward dolls, whereas males tend to go for “boys’ toys” such as trucks.
The new findings are based on 14 years of studies of the Kanyawara chimpanzee community at Uganda’s Kibale National Park. Wrangham and co author Sonya Kahlenberg of Bates College in Maine found that chimpanzees use sticks in four main ways: as probes to investigate holes potentially containing water or honey, as props or weapons in aggressive encounters, during solitary or social play, and in a behavior the re searchers call stick-carrying.
Wrangham said they had seen stick-carrying from time to time over the years and suspected females were doing it the most. Detailed investigation has confirmed that, they added. “We thought that if the sticks are being treated like dolls, females would carry sticks more than males do and should stop carrying sticks when they have their own babies,” Wrangham said. “Both of these points are correct.”
Young females some times took their sticks into day-nests where they rested and some times played with them casually in a manner that evoked maternal play, the researchers reported.
It’s not yet clear whether this form of play is common in chimpanzees, the researchers say. In fact, no one has previously reported stick-carrying as a form of play, despite consider ble interest among chimpanzee researchers in describing object use. “This makes us suspect that stick-carrying is a social tradition that has sprung up in our community and not others,” Wrangham said.
Because stick-carrying is uncommon even in the Kanyawara chimps that Wrang ham and Kahlenberg studied, they said, they won’t be sure until researchers study ing other communities report its absence. They note that chimp play is generally poorly documented because chimp communities are usually small with few youngsters at any one time."
