Rhythmic behaviors (in short RBs), such as applauding, dancing or rocking a baby to sleep are part of humans everyday life. Recently there has been a growing interest in the RBs of other species, as a way of tracking the evolutionary roots of human musicality. RBs have been initially studied in arthropods, insects, anurans and songbirds, where a single behaviour is tied to reproductive function. Emergent evidence shows that this connection extends to some mammalian species as well. Very little is known, however, about the presence of RBs and their likely adaptive significance in our closest genetic relatives - the chimpanzees (Pan troglodytes). Evidence is limited to mentions of rocking during courtship, or as abnormal behaviour in captivity, and to descriptions of so-called “buttress drumming”. This “drumming”, whose function remains controversial, is very different from musical rhythmicity, as it is aperiodic, and results typically from 2-5 foot stomps on a resonant surface.To address the absence of data on chimpanzee RBs and their likely functional relevance, we conducted an observational study, and recorded RBs in the contexts in which they occurred. One aim of this study was to examine the context specificity of RBs in chimpanzees, i.e. to investigate if particular RBs are context-bound, thus having a specific function (e.g. facilitating reproduction like in other species) or if they are flexibly presented in a variety of contexts, without being obligatory in one specific context. Observations were collected from 4 chimpanzee groups housed at Lund University Primate Research Station Furuvik, Sweden (61 h) and MONA Foundation, Spain (57,5 h). Preliminary results suggest that RBs are frequent in chimpanzees, i.e. in the currently analysed data subset consisting of 18,5 observation hours from Furuvik we recorded 262 bouts, of which 246 were constituted by one of 7 highly frequent RB. An RB x Context chi-square test showed that RBs types were not independent from contexts (χ2= 548, df = 64, P < 0.001). Two RBs showed context exclusivity (p < 0.01, binomial test): teeth clacking (N=30) occurred only during grooming, and copulatory display (N=14) occurred only during courtship. One RB - surface hitting (N=31) - was primarily used for initiation of social interaction (p < 0.05, binomial test). Four additional RBs that occurred frequently (≥ 19) were not tied to a specific context. Overall, the RB exhibited by chimpanzees appeared to accomplish a communicative purpose.
References:Arcadi, A.C., & Wallauer, W. (2013). They Wallop Like They Gallop: Audiovisual Analysis Reveals the Influence of Gait on Buttress Drumming by Wild Chimpanzees (Pan troglodytes). International Journal of Primatology, 34, 194-215.Goodall J, van L. (1968) The behaviour of free-ranging chimpanzees in the Gombe Stream Reserve. Animal Behavior Monographs, I:161-311.Lopresti-Goodman, S. M., Kameka, M., & Dube, A. (2012). Stereotypical behaviors in chimpanzees rescued from the african bushmeat and pet trade. Behavioral sciences, 3(1), 1–20.Hoeschele M, Merchant H, Kikuchi Y, et al. (2015). Searching for the origins of musicalityacross species. Philosophical Transactions of the Royal Society B: Biological Sciences 370:20140094.Ravignani A. (2019). Rhythm and synchrony in animal movement andcommunication. Current Biology, 65(1), 77-81.Greenfield M.D., (2005). Mechanisms and Evolution of Communal SexualDisplays in Arthropods and Anurans. Advances inthe Study of Behavior 35:1-62