The Malagarasi River has long been thought to be a barrier to chimpanzee movements in western Tanzania. We present four hypotheses on the functional origin and on the learning process of this cultural behavioral pattern. Social scratch was not lateralized to left or right. However, when lactating females social scratched to infants or juveniles, they scratched other body parts. Social scratch was directed mostly to the dorsal side of the body. These facts indicate some social function of the behavior. Frequencies of social scratch per grooming bout among adult and adolescent males, and from lactating females to infants or juveniles, were high, and among males, higher-ranking males especially received more. Frequency of social scratch was correlated with frequency of social grooming, but not with frequency of self-scratch. This behavioral pattern of 'social scratch' is another example of locality-specific social behavior, or custom, as it is not found in the Gombe National Park, Tanzania, about 150 km north of Mahale, nor has it been reported from any other sites of chimpanzee study. The ritualized behavioural display and collection of artefacts at particular locations observed in chimpanzee accumulative stone throwing may have implications for the inferences that can be drawn from archaeological stone assemblages and the origins of ritual sites.Ĭhimpanzees (Pan troglodytes schweinfurthii) in the Mahale Mountains National Park, Tanzania, scratch other individuals' bodies while they groom them. This represents the first record of repeated observations of individual chimpanzees exhibiting stone tool use for a purpose other than extractive foraging at what appear to be targeted trees. We found four populations in West Africa where chimpanzees habitually bang and throw rocks against trees, or toss them into tree cavities, resulting in conspicuous stone accumulations at these sites. In addition to data from 17 mid- to long-term chimpanzee research sites, we sampled a further 34 Pan troglodytes communities. Here, we describe newly discovered stone tool-use behaviour and stone accumulation sites in wild chimpanzees reminiscent of human cairns. Comparatively, stone tool use among living primates has illuminated behaviours that are also amenable to archaeological examination, permitting direct observations of the behaviour leading to artefacts and their assemblages to be incorporated. The study of the archaeological remains of fossil hominins must rely on reconstructions to elucidate the behaviour that may have resulted in particular stone tools and their accumulation. Our evidence indicates that matrilineal inheritance can be sufficiently strong in nonhuman primates to account for long-term differences in community traditions.
Matrilineal inheritance of socially learned behaviors has previously been reported for tool use in chimpanzees and in the vocal and feeding behavior of cetaceans. However, frequencies of PPC were highly consistent within matrilines, indicating that individuals maintained lifelong fidelity to the grooming style of their mothers. We found that in the Kanyawara community (Kibale, Uganda), adults of both sexes varied widely in their PPC frequency (from 50%) and did not converge on a central group tendency. Here, we examine factors responsible for individual variation in PPC frequency within a single wild community.
Because between-community differences in frequency of PPC apparently result from social learning, are stable across generations, and last for at least 9 years, they are thought to be cultural, but the mechanism of transmission is unknown. In wild communities, samples of at least 100 observed dyads grooming with raised hands showed PPC frequencies varying from 30% dyads grooming (Kanyawara, Kibale), and in a large free-ranging sanctuary group, the frequency reached >80% dyads (group 1, Chimfunshi). Palm-to-palm clasping (PPC) is a distinct style of high-arm grooming in which the grooming partners clasp each other's raised palms. High-arm grooming is a form of chimpanzee grooming in which two individuals mutually groom while each raising one arm.
0 kommentar(er)
