Chimpanzee (Pan troglodytes verus) Behavioral Responses to Stresses Associated with Living in a Savannah-Mosaic Environment: Implications for Hominin Adaptations to Open Habitats

Abstract

Anthropologists have long been interested in the behavioral ecology of nonhuman primates living in savannas given what we know of early hominin environments. As expected, chimpanzees in the Fongoli community in southeastern Sénégal show a unique suite of behavioral adaptations to stresses associated with their savanna habitat. While Fongoli chimpanzees are species-typical in certain regards, such as including ripe fruit in the diet during all months of the year, they also adjust their behavior to the particular stresses of this dry, hot and open environment. These behaviors include using caves as shelters during the dry season, soaking in pools of water during the hot, early rainy season, and traveling and foraging at night during maximum phases of the moon. Adult males of this 35-member community serve as focal subjects in a long-term study of the ecology and behavior of chimpanzees in a savanna-mosaic environment. Here, we report on Fongoli chimpanzee activity budgets, grouping behavior, and habitat use during the dry versus wet season based on over 2500 hours of observation from March 2005-July 2006. Findings support the hypothesis that ecological pressures associated with a savanna environment significantly affect great ape behavior. The Fongoli chimpanzees' large home range (>65km²) is sometimes used cyclically, with the community traveling as one large party, in contrast to the typical chimpanzee fission-fusion pattern. Combined with data on temperature in the various habitats within the savanna mosaic, results show that Fongoli chimpanzees minimize energy expenditure during the hottest months and at the hottest time of day by resting more and traveling less, in addition to selectively using small patches of closed-canopy habitats, such as gallery forest. They move significantly more during early hours of the hot, dry season specifically and range in smaller parties at this time compared to during the wet season. The stresses associated with a savanna-mosaic environment and chimpanzees' behavioral adjustments to them have important implications for understanding early hominin behavior in similar environments.

High Prevalence of Simian Immunodeficiency Virus Infection in a Community of Savanna Chimpanzees

“…Testing fecal samples from just two collection sites yielded a number of unexpected results. First, we found that the 67 Issa Valley chimpanzees all shared the same home range, indicating a community size much larger than that of other known savanna chimpanzees (4,34,46). Second, we discovered SIVcpz infection among these apes, indicating that there was, in fact, a second area of SIVcpz endemicity in Tanzania.…”

“…The finding of 67 individuals within the Issa Valley study area, 64 of whom were interconnected by joint nesting episodes or diurnal associations, was surprising. Other known savanna chimpanzee communities are either much smaller (28 to 35 individuals) (4,34) or from sites with appreciably greater population densities (0.2 to 0.7/km 2 ) (14,46). The significance of such a large community (a minimum of 67 individuals) living at such a low density (less than 0.14 individual/km 2 ) is that the implied home range is enormous, i.e., greater than 478 km 2 , which is nearly twice the size of the largest similarly estimated home range published to date (4).…”

“…Because of their challenging environment, savanna chimpanzees are also predicted to differ in aspects of their behavior and social structure from forest chimpanzees (24,25). Finally, they are often used as a model system for the behavioral ecology of early hominids, who are believed to have evolved in similar habitats (24,34). Here, we report the first survey of savanna chimpanzees for SIVcpz infection.…”

Water, plants, and early human habitats in eastern Africa

“…In semiarid regions, precipitation primarily determines water availability (15). Today, water availability shapes primate behaviors through its influence on vegetation and resource distributions (4,61). For example, regions with MAP <700 mm do not support chimpanzee populations (62).…”

In search of the last common ancestor: new findings on wild chimpanzees

“…However, they enter surface water in certain circumstances: at Fongoli, they immerse themselves in temporary rain-filled pools at the beginning of the rainy season, when it is still hot and humid; there they rest, groom and play (Pruetz & Bertolani 2009). Thus, water becomes a thermoregulatory device, even when potentially risky.…”