By Sujata Gupta
From deep inside chimpanzee territory, the fieldworkers heard loud bangs and shouts. Hidden video cameras later revealed what the chimps in the Boé region of Guinea-Bissau were up to. Males were throwing rocks at trees and yelling.
Researchers don’t fully understand why the apes engage in this rare behavior, known as accumulative stone throwing. And scientists may not have much time to sort out what’s going on.
All four of Africa’s subspecies of chimpanzees are under threat from deforestation and poaching. That and other human activity may also be affecting chimp behaviors, including ones that many primatologists view as evidence of chimp culture — behaviors that are learned socially and transmitted through generations, Ammie Kalan and colleagues report online March 7 in Science. Such traditions as cave dwelling, using sticks to dig for honey and cracking nuts with stones are far less likely to occur in areas most impacted by humans, compared with more remote chimp territories, the team found.
“Everyone thinks that if populations are declining … there would be some loss in the transmission chain that leads to cultural diversity in animals,” says Kalan, of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. “We’re the first to really show this.”