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Chimpanzees are renowned for their use of foraging tools in harvesting social insects and some populations use tools to prey on aggressive army ants ( Dorylus spp.). Tool use in army ant predation varies across chimpanzee study sites with differences in tool length, harvesting technique, and army ant species targeted. However, surprisingly little is known about the detailed ecology of army ant predation. We studied army ant predation by chimpanzees ( Pan troglodytes verus) at the Seringbara study site in the Nimba Mountains, Guinea (West Africa), over 10 years (2003-2013). We investigated chimpanzee selectivity with regards to army ant prey species. We assessed the temporal variation in army ant-feeding and examined whether army ant predation was related to rainfall or ripe fruit availability. Moreover, we examined whether chimpanzees showed selectivity regarding plant species used for tool manufacture, as well as the relationship between tool species preference and tool collection distance. Lastly, we measured tool properties and investigated the use of tool sets and composite tools in army ant predation. Seringbara chimpanzees preyed on one army ant species ( D. nigricans) more often than expected based on encounter rates, which may be explained by the overlap in altitudinal distribution between chimpanzees and D. nigricans. Army ant predation was not related to rainfall or fruit availability. Chimpanzees were selective in their choice of tool materials and collected their preferred tool species ( Alchornea hirtella) from greater distances than they did other species. Lastly, Seringbara chimpanzees used both tool sets and composite tools (tree perch) in army ant predation. Tool types (dig vs. dip) differed in width and strength, but not length. Tool composites were found at 40% of ant-feeding sites. Our study sheds new light on the ecology of army ant predation and provides novel insights into chimpanzee selection of army ant prey and tool species. Am. J. Primatol. 77:319-329, 2015. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Geographical variation in behaviour may be best explained in terms of culture if ecological and genetic explanations can be excluded. However, ecological conditions and genetic predispositions may in turn also affect cultural processes. We examined the influence of environmental factors on foraging tool use among chimpanzees at the Seringbara study site in the Nimba Mountains, Guinea, where nut cracking and termite fishing are absent, but ant dipping is present. We tested two ecological hypotheses to explain foraging tool use prevalence. The opportunity hypothesis states that encounter rates with nuts, insects or tools explain tool use patterns. We measured the density and distribution of nut trees, nuts, army ants, termites and potential tools in relation to the chimpanzees'' ranging patterns. The necessity hypothesis states that tool use is a response to scarcity of preferred foods (i.e. ripe fruit). We measured the temporal availability of nuts, army ants and termites in relation to preferred food sources. Our findings support the opportunity hypothesis: nut trees and Macrotermes mounds were rare and peripheral to the chimpanzees'' range, whereas army ants were abundant and widespread. The necessity hypothesis did not explain tool-assisted insectivory, as both army ants and termites were available during ripe fruit scarcity, yet neither ant dipping nor termite fishing functioned as fallback strategies. Nuts were absent at times of fruit scarcity and were not available as fallback foods. Our findings highlight the importance of considering environmental conditions in explaining foraging tool use by wild chimpanzees and emphasize the interplay between environment and culture. [Copyright &y& Elsevier]

The construction of nests (or beds) for sleeping is a chimpanzee universal, yet little is known about the adaptive function of nest-building. We present an in-depth study of nest-building by unhabituated chimpanzees at the Seringbara study site in the Nimba Mountains, Guinea, West Africa. We recorded 1520 chimpanzee nests over 28 mo during three study periods between 2003 and 2008. We investigated where chimpanzees built their nests, both across the home range and in nest trees, and assessed how altitude and habitat type affected nest site selectivity. We examined whether or not chimpanzees were selective in nest tree choice regarding physical tree characteristics and tree species and assessed plant species preference for both tree- and ground-nesting. We tested three, nonmutually exclusive, hypotheses for the function of arboreal nest-building. We assessed whether selectivity for nest tree characteristics reflected an antipredator strategy, examined whether nesting patterns (both arboreal and terrestrial) and nesting height were influenced by variation in climatic conditions (temperature, humidity, wind), and measured mosquito densities at ground level and in trees at 10 m and related mosquito densities to nesting patterns. Chimpanzees preferred to nest above 1000 m and nested mainly in primary forest. They preferred relatively large trees with a low first branch, dense canopy, and small leaves and showed preference for particular tree species, which was stable across years, whereas plant choice for ground-nesting was largely based on plant availability. We found no support for the antipredation hypothesis, nor did mosquito densities explain arboreal nest-building. The thermoregulation hypothesis was supported, as both nesting patterns and nest-height variation across seasons reflected a humidity-avoidance strategy. Chimpanzees nested higher in trees and at higher altitudes in the wet season. In sum, chimpanzees were selective in their choice of nest sites, locations, and materials, and tree-nesting patterns at Seringbara were best explained by a thermoregulation strategy of humidity avoidance. [ABSTRACT FROM AUTHOR]