Chimpanzees (Pan troglodytes) Flexibly Use Introduced Species for Nesting and Bark Feeding in a Human-Dominated Habitat

Abstract

As habitat loss and fragmentation place growing pressure on endangered nonhuman primate populations, researchers find increasing evidence for novel responses in behavior. In western Uganda between the Budongo and Bugoma Forests, chimpanzees (Pan troglodytes schweinfurthii) inhabit a mosaic landscape comprising forest fragments, human settlements, and agricultural land. We recorded nests and feeding evidence of unhabituated chimpanzees in this region over a 12-mo period. We found extensive evidence of nesting in introduced tree species, including eucalyptus (Eucalyptus grandis), guava (Psidium guajava), cocoa (Theobroma cacao), and Caribbean pine (Pinus caribaea). In addition, we found instances of ground nesting, nest reuse, and composite nests constructed from branches of multiple trees. This evidence may indicate a lack of suitable nesting trees or attempts by chimpanzees to nest in areas of riparian forest that allow them to avoid human detection. We also found new evidence for eucalyptus bark feeding by chimpanzees. Such evidence suggests chimpanzees respond flexibly to mitigate anthropogenic pressures in human-dominated landscapes. The limits of such flexibility remain unknown. Further research is needed to examine systematically the factors influencing the use of such resources and to understand better the extent to which chimpanzees can persist while relying on them.

Keywords: Bark feeding; Chimpanzee; Eucalyptus nesting; Fragmented habitat; Pan troglodytes.

Fig. 1

Map of the study area in Uganda. The inset map displays the landscape’s location within Uganda. Green indicates forest cover during the study period (Hansen et al. 2013).

Fig. 2

Chimpanzee nest locations throughout the study area, western Uganda, from October 2012 to September 2013. Individual chimpanzee nests are indicated as black circles. Not all nests are visible because of map scaling. MCPs for Wagaisa and Kiryangobe are indicated by polygons. Green indicates forest cover during the study period (Hansen et al. 2013).

Fig. 3

Chimpanzee eucalyptus bark feeding signs and direct observation, Hoima District, Uganda. (a) Direct observation of eucalyptus bark feeding by a mixed chimpanzee party, January 2013. (b) The base of a eucalyptus tree with evidence of chimpanzee bark stripping.

Fig. 4

Locations associated with eucalyptus bark feeding evidence during the study period, October 2012 to September 2013. Black circles indicate the locations of chimpanzee bark feeding evidence or direct observations. MCPs for Wagaisa and Kiryangobe are indicated by polygons. Green indicates forest cover during the study period (Hansen et al. 2013).