1Lester Fisher Center for the Study and Conservation of Apes, Lincoln Park Zoo, 2Congo Program, Wildlife Conservation Society, 3Department of Earth and Planetary Sciences, Washington University, 4Anthropology Department, Washington University
April 15, 2016 11:00, A 706/707
One of the unique behavioral aspects that distinguish great apes from other primates is the consistent construction of night nests. Variation in nest building has been well-documented among apes, with the most consistent difference being between gorillas and other apes. Gorillas show a greater propensity to select terrestrial nesting locations, while other great apes tend to build arboreal nesting platforms. Comparisons between sympatric ape species can aid in identifying specific factors that modulate inter-individual spacing in the context of sleeping. In this study, we examine the spatial dimensions of nesting by western lowland gorillas (Gorilla gorilla gorilla) and central chimpanzees (Pan troglodytes troglodytes) in Republic of Congo. From 2001 to 2012, a total of 12,467 ape nests were encountered along line transects in the Goualougo Triangle study area. 2D and 3D nearest neighbor distances were calculated between individual nests within a site. We encountered 4,745 sites with multiple nests which represents a social group of nesting apes. Thirty-five percent of the nest sites were attributed to gorillas, with the remainder being chimpanzee nests. Nearest neighbor distances were lower among gorillas than matched chimpanzee nest groups. Distance between ape nests was related to group size, habitat type, nesting materials, and risk of predation. We also examine nest spacing along a gradient from pristine forest to regions being actively logged to determine the effect of anthropogenic disturbance on ape nesting. Flexibility in the construction of these vegetative “artefacts” provides compelling evidence of the technological skill of our closest living relatives.