The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)

Ethological Study of Manual Laterality in Sanctuary Chimpanzees (Pan troglodytes)


Anthropology, Miami University

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The study of manual laterality in nonhuman primates figures in some models that seek to explain the evolution of cerebral lateralization in Homo sapiens (e.g., MacNeilage, 1987). The nature of laterality in chimpanzees (Pan troglodytes) is debated with much of the disparity derived from methodological concerns and contrasting results from field and captive studies. This study used ethological methods to observe chimpanzees in a semi-natural environment. Given the results of wild laterality studies, excluding tool-use, we hypothesized that few behavioral patterns would be biased, when individuals had hand preferences these biases would not generalize across patterns, and no group-level bias would emerge.

Data were collected from 22 individuals (15 females and 7 males) in Enclosure 2 of the Chimfunshi Wildlife Orphanage, Zambia, in July 2012 using McGrew and Marchant’s 2001 ethogram of 35 patterns of hand use. Data were collected using continuous focal animal sampling. A total of 1258 observations of hand use were recorded. Binomial tests were subsequently performed on the 9 most frequent behaviors.

Of the 55 analyses performed, 6 analyses of 4 behaviors and 5 individuals yielded statistical significance. An adolescent male exhibited biases in 2 behaviors, though with opposite hands. Additionally, for 2 other patterns, Nose Wipe and Pick Up, more than 1 individual exhibited a bias, though not with the same hand. Based on these results, we conclude that naturalistically housed chimpanzees exhibit no greater manual biases (in non-tool related behaviors) than wild chimpanzees.

Research support provided by three Miami University funds - the Rebecca Jeanne Andrew Memorial Award, the Ronald and Judith Spielbauer Student Achievement Fund, and the University of Cambridge Junior Fellows Fund.

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