Chimpanzees develop specific handshake-like gestures depending on their social group, according to the results of a 12-year observational study published on Wednesday that sheds light on the animalsâ complex social structures.
Chimps are often referred to as being the most âhumanlikeâ non-human species, given their propensity to perform complicated tasks, such as tool use, which were long thought to be the sole preserve of mankind, report BSS.
Edwin van Leeuwen, an expert in animal behaviour at the University of Antwerp and the cityâs Royal Zoological Society, studied dozens of chimpanzees sheltered at Zambiaâs Chimfunshi Wildlife Orphanage Trust over a 12-year span.
Despite a large turnover in the chimp population due to deaths and births, Van Leeuwen was able to observe specific and repeated hand gestures among chimps in two distinct groups.
The gesture, known as the grooming handclasp, involves âeach of the participants simultaneously (extending) an arm overhead and the other (clasping) the otherâs wrist or hand or both clasping each otherâs hand,â according to the results of his study, published in the journal Royal Society Biology Letters.
Through years of observation, Van Leeuwen found that palm-to-palm grasping was âsubstantially more pronouncedâ in one group, or society, of chimps than the other.
He also found that female chimps were far more likely than males to grasp palms, while males were more likely to grasp wrists, likely due to malesâ desires to assert or affirm dominance.
âThe fact that they have developed different styles in different groups reflects that they learn the style socially within their groups,â Van Leeuwen told AFP.
He said the chimps appeared to have learned to perform the grasps âto some extentâ as a ritual, reminiscent of secret handshakes performed by humans.
âThe handclasp fits into the whole social interaction that two individuals engage in sometimes, making it a special connection within an already intimate grooming bout.â
Van Leeuwen said his study was evidence of chimpsâ ability to preserve âthe stability of traditionsâ, a behaviour that among humans is thought of as cultural persistence.
He said the behaviour could not be explained by genetic or environmental factors since the composition of the two separate chimp groups was essentially identical â yet they each developed distinct grasping techniques.
He said the specific gestures and their longevity within each group could be a result of âthe shared trait of social learningâ.
With more than a decade spent observing the chimpsâ behaviour, Van Leeuwen said he got to know the personality traits of each individual animal.
âLike humans, they have their individual ways of doing â be it during play, eating or grooming,â he said.
âSome chimpanzees are very serious, always on the look-out for ripples in the social atmosphere,â added Van Leeuwen.
âSome are more care-free and interact with even high-ranking individuals in their group with light touches of play.â