Dietary responses to fruit scarcity of wild chimpanzees at Bossou, Guinea: Possible implications for ecological importance of tool use

Abstract

A 13-month ecological study was conducted at Bossou, Guinea, West Africa, to elucidate how a community of wild chimpanzees (Pan troglodytes verus) deals with the scarcity of main foods. During the study period, fruit availability fluctuated radically. The chimpanzees were confirmed to depend heavily on three "keystone resources" which were available when their main foods (fruit pulp) were scarce. These were fruits of Musanga cecropioides, oil-palm (Elaeis guineensis) nuts, and oil-palm pith. These are abundant in the chimpanzees' home range and their nutritional contents compensate for a decrease in nutritional intake from fruit pulp. The presence of these excellent backup foods may explain the high reproductive performance of Bossou chimpanzees. Here, chimpanzees consumed two of the three keystone foods using two types of tool behavior: nut-cracking for oil-palm nuts and pestle-pounding for oil-palm pith. These tool-using behaviors accounted for 31.9% of the total feeding time spent in June (the month in which the highest frequency occurred) and 10.4% in total for the year. It is suggested that the Bossou chimpanzees depend strongly on tools for their subsistence. This implies a possible function for tool technology in the evolution of our human ancestors.

Ecological and social correlates of chimpanzee tool use

“…This seems feasible in the case of pestle pounding of oil palms and cracking of nuts among chimpanzees of Bossou in Guinea [31] and the nut cracking of Tai chimpanzees in Ivory Coast [33]. Although the food items harvested with tools are a rich source of nutrients, they comprise a rstb.royalsocietypublishing.org Phil Trans R Soc B 368: 20120416…”

“…By contrast, tools were rarely used by finches in a zone where food was abundant and easily accessible. Chimpanzees increased use of tools during periods of fruit scarcity at Bossou, Guinea [31]. Additional suggestions of tool use during times of necessity have been asserted for bearded capuchins in northeastern Brazil [45] and long-tailed macaques in Thailand [43], but the necessity hypothesis was not explicitly tested in these particular studies.…”

“…However, there is relatively little information within these manuscripts to assess the invention hypothesis, and the relative profitability hypothesis was only recently outlined (Rutz et al [30]; Rutz & St Clair [22]), so remains to be empirically examined in most of these taxa/populations. Sources (page numbers refer to original publications): b Yamakoshi [31]. c Koops et al [32].…”

The reluctant innovator: orangutans and the phylogeny of creativity

“…The natural history of innovation in large-brained and long-lived species such as great apes: contexts in which novel behaviour patterns may arise. [47,48]. There is no evidence for this in orangutans [43,49], nor in chimpanzees and bearded capuchin monkeys [43], although others have suggested it is important among chimpanzees and capuchin monkeys [47,48].…”

“…[47,48]. There is no evidence for this in orangutans [43,49], nor in chimpanzees and bearded capuchin monkeys [43], although others have suggested it is important among chimpanzees and capuchin monkeys [47,48]. In the case of orangutans, populations with more bark feeding (which happens in response to food scarcity) have smaller innovation repertoires [50].…”