August 30, 2012
‘Grooming Handclasp’ Used By Some Chimpanzees As A Social Tradition
April Flowers for redOrbit.com - Your Universe Online
Chimpanzees are capable of learning from one another and they use this social interaction to create and maintain local traditions.A team of researchers from the Gonzaga University and the Max Planck Institute for Psycholinguistics in Nijmegen, Netherlands, has published a new study showing that the ways in which chimpanzees groom each other depends on the community to which they belong.
The team focused on one single behavior, the 'grooming handclasp.' Two chimps clasp onto each other's arms, raise the clasped arms up in the air, and then groom each other with their free hands. This behavior has only been observed in some chimpanzee populations, which led researchers to ask if it was an instinctive behavior or a learned one passed on to subsequent generations.
Between 2007 and 2012, Edwin van Leeuwen and Katherine Cronin of the Comparative Cognitive Anthropology research group of the Max Planck Institute conducted their observations at the Chimfunshi Wildlife Orphanage Trust in Zambia. A mix of captive-born and wild-born chimpanzees live in woodlands in some of the largest enclosures in the world, at Chimfunshi.
Previous research suggested that the grooming handclasp might be a cultural phenomenon, just as humans across cultures engage in different ways of greeting each other. These suggestions, however, were based on observations that some chimpanzee communities handclasp and others do not. They did not take into consideration whether there were differences between the communities that engage in handclasping. Early observations could have been explained by differences in genetics and/or ecological factors between the chimpanzee communities, which precluded the interpretation that the chimpanzees were exhibiting 'cultural differences."
The new data shows that even between communities that engage in the grooming handclasp, subtle yet stable differences exist in the styles that they prefer. One group highly preferred the style where they would grasp each other's hands during the grooming, while another group engaged in a style where they would fold their wrists around each other's wrist.
"We don't know what mechanisms account for these differences", van Leeuwen says. "But our study at least reveals that these chimpanzee communities formed and maintained their own local grooming traditions over the last 5 years. Our observations may also indicate that chimpanzees can overcome their innate predispositions, potentially allowing them to manipulate their environment based on social constructs rather than on mere instincts."
The team observed, that even apart from the style preferences of the communities, the grooming handclasp behavior was a long-lasting part of the behavioral repertoire which was transmitted to the next generation of potential handclaspers.
"By following the chimpanzees over time, we were able to show that 20 young chimpanzees gradually developed the handclasp behavior over the course of the five-year study. The first handclasps by young individuals were mostly in partnership with their mothers. These observations support the conclusion that these chimpanzees socially learn their local tradition, and that this might be evidence of social culture", Max Bodamer of Gonzaga University explains.
"Continued monitoring of these groups of chimpanzees will shed light on the question of how these group-traditions are maintained over time and potentially even why the chimpanzees like to raise their arms up in the air during social grooming in the first place", van Leeuwen adds.
The study is published in Proceedings of the Royal Society B.