In this dissertation I examine the behavioral ecology of savanna chimpanzees in Senegal. I test hypotheses related to the effects of the environment on the diet of the chimpanzees at Fongoli, concentrating on their insectivory specifically. Fongoli is the hottest and driest site in which chimpanzees have been habituated for observational data collection. Grassland habitats (68%) dominate, characterizing the site as an open savanna mosaic, which is interspersed with woodland and small patches of closed forests. The environment at Fongoli presents a setting similar to that of Plio-Pleistocene hominans (Bobe & Behrensmeyer 2004, Bromage & Schrenk 1995, Cerling 1992, Reed 1997) and provides the opportunity to examine the behavior of apes in response to selective pressures associated with such an environment.
I examine Fongoli chimpanzee insectivory in the larger context of activity and habitat use, with an emphasis on evaluating potential ecological influences in this environment. Most chimpanzee research over the last 40 years has emphasized behavior, with limited data on the ecological context. Here, I provide detailed data on food distribution and availability, using both plot and plotless methods.
A major question I examined was whether termites were an important food resource for the Fongoli chimpanzees. Chimpanzees are highly frugivorous and usually rely on a few important food species, yet as omnivores, also incorporate animal prey in their diet. My previous research indicated that Fongoli chimpanzees often fished for termites with tools. I predicted that the environment of these savanna chimpanzees affected insect foraging. Thus, I expected that ecological factors at Fongoli influenced their insectivorous behavior and hypothesized that certain habitats were more important for feeding (open habitats), while other habitat types (closed habitats) were used mainly for resting and social behaviors.
Over 900 hours of observation provided behavioral data on insect foraging, general activity, general diet, and habitat use of chimpanzees. Fongoli chimpanzees consume termites (Macrotermes subhyalinus) more often than any other chimpanzee population studied. The chimpanzee diet at Fongoli is composed mostly of fruit (61.3%) and termites (24.1%). Although termites were consumed throughout the year, with a peak during the transitional period to the beginning of the wet season, the inclusion of termites in the diet did not correlate significantly with rainfall or fruit scarcity. Termites are an essential resource for the Fongoli chimpanzees throughout the year, and chimpanzees spend an annual average of approximately 8% of their active time termite fishing. High soil and air temperatures correlated to greater proportion and longer bout length of termite fishing. Fongoli chimpanzees forage for termites most often in woodland habitat types. General foraging and feeding was conducted primarily in woodland and grassland habitat types, where all food resources exhibited the highest densities. While seasonality had no affect on termite foraging, seasonality did influence feeding and foraging behavior in general, in that more time was devoted to these activities in the dry season (November through May) when fruits are more abundant.
The extensive termite feeding of Fongoli chimpanzees adds to the list of distinctive behaviors they display relative to chimpanzees living in more forested habitats (Pruetz 2001, 2007, Pruetz & Bertolani 2007). I incorporate the Fongoli chimpanzees' behaviors in a relational model of hominan evolution. I found that these chimpanzees consume termites more than any other ape community across Africa. The relatively few mammalian prey species, high temperatures correlating with increased termite fishing, and abundant density of Macrotermes in savanna woodland habitat types at Fongoli are all variables indicating environmental influence on termite foraging. Paleoanthropologists can use these data to construct testable hypotheses about the ecology of hominan habitats. Environmental stresses associated with savanna paleo-habitat would likely be comparable to what is found at Fongoli. Hominan species living in similar habitats may have relied on termites as an animal resource when other foods were scarce resembling Fongoli chimpanzees. Finally, data in this thesis should also be brought to bear on the conservation of chimpanzees' habitats. Emphasis on protecting closed forest habitats is usually a focus in conservation efforts. However, woodland and grassland habitat types contain the majority of the important food resources of the Fongoli chimpanzees and should be conserved to ensure the long-term survival of the West African chimpanzees in southeastern Senegal.
|Location of Publication||Ames, Iowa|
|Degree||Doctor of Philosophy, Ecology and Evolutionary Biology|
|Notes||This thesis was found at the Digital Repository for Iowa State University: http://lib.dr.iastate.edu/|
|University||Iowa State University|
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