By using five years of observation on neighboring communities of chimpanzees at the Chimfunshi Wildlife Orphanage in Zambia, an international team of scientists has shown that chimpanzees are not only capable of learning from one another, but also use social information to form and maintain local traditions.
The specific behavior that the team focused on was the ‘grooming handclasp,’ a behavior where two chimpanzees clasp onto each other’s arms, raise those arms up in the air, and groom each other with their free arm. This behavior has only been observed in some chimpanzee populations. The question remained whether chimpanzees are instinctively inclined to engage in grooming handclasp behavior, or whether they learn this behavior from each other and pass it on to subsequent generations.
At Chimfunshi, wild- and captive-born chimpanzees live in woodlands in some of the largest enclosures in the world. The team collaborated with local chimpanzee caretakers in order to collect and comprehend the detailed chimpanzee data. Previous studies suggested that the grooming handclasp might be a cultural phenomenon, just like humans across cultures engage in different ways of greeting each other. However, these suggestions were primarily based on observations that some chimpanzee communities handclasp and others don’t – not whether there are differences between communities that engage in handclasping. Moreover, the early observations could have been explained by differences in genetic and/or ecological factors between the chimpanzee communities, which precluded the interpretation that the chimpanzees were exhibiting ‘cultural’ differences.
A new study shows that even between chimpanzee communities that engage in the grooming handclasp, subtle yet stable differences exist in the styles that they prefer: one chimpanzee group highly preferred the style where they would grasp each other’s hands during the grooming, while another group engaged much more in a style where they would fold their wrists around each other’s wrists.