Dialects in leaf-clipping and other leaf-modifying gestures between neighbouring communities of East African chimpanzees

Abstract

Dialects are a cultural property of animal communication previously described in the signals of several animal species. While dialects have predominantly been described in vocal signals, chimpanzee leaf-clipping and other ‘leaf-modifying’ gestures, used across chimpanzee and bonobo communities, have been suggested as a candidate for cultural variation in gestural communication. Here we combine direct observation with archaeological techniques to compare the form and use of leaf-modifying gestures in two neighbouring communities of East African chimpanzees. We found that while both communities used multiple forms, primarily within sexual solicitation, they showed a strong preference for a single, different gesture form. The observed variation in form preference between these neighbouring communities within the same context suggests that these differences are, at least in part, socially derived. Our results highlight an unexplored source of variation and flexibility in gestural communication, opening the door for future research to explore socially derived dialects in non-vocal communication.

Social dynamics of vervet monkeys are dependent upon group identity

“…Overall, our results add to previously published studies which offer evidence for the existence of social traditions in bonobos 85 , chimpanzees 86,87,88 , capuchins 54,89 , spider monkeys 32,31 and baboons 16,37 .…”

Social dynamics of vervet monkeys are dependent upon group identity

“…Interestingly, cases where dispersing males bring their individual knowledge to their new group after dispersal have also been reported, however, such observation often concerns food-related and material traditions 80 , 81 , 82 , 83 , 84 and have rarely been reported in social traditions. 55 , 84 , 85 Overall, our results add to previously published studies which offer evidence for the existence of social traditions in bonobos, 86 chimpanzees, 87 , 88 , 89 capuchins, 55 , 90 spider monkeys 32 , 33 and baboons. 16 , 38 …”

Object use in communication of semi-wild chimpanzees

“…This effect could be explained by some targeted object actions such as touching, hitting, and poking being exclusively tactile, which was not the case for any of the nontargeted object actions. Nevertheless, since self-grooming and spitting were limited to specific colonies, and knowing that some gestures may be socially learned (Pika et al 2003 ; Badihi et al 2023 ), our findings suggest that there may be promise in further investigation of colony differences in specific object action types. When doing so, consideration should be extended to the fact that differences in group dynamics and social density may lead to unequal opportunities for socialisation across colonies (Cronin et al 2014 ; Rawlings et al 2023 ).…”

“…While the evidence remains limited in communication there has also been only limited investigation of the question (but c.f. Badihi et al 2023 ), thus, it seems reasonable to hypothesize that chimpanzees may also learn socially about object interactions and as a result we predict that these interactions will differ between colonies (H3: group specific variation). Our findings will improve our understanding of the extent to which social groups of nonhuman primates may differ in their nonvocal signals, which have traditionally received less attention (Davila-Ross et al 2011 ; Lameira 2013 ).…”