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Primate social organizations, or grouping patterns, vary significantly across species. Behavioral strategies that allow for flexibility in grouping patterns offer a means to reduce the costs of group living. Chimpanzees (Pan troglodytes) have a fission‐fusion social system in which temporary subgroups ("parties") change in composition because of local socio‐ecological conditions. Notably, western chimpanzees (P. t. verus) are described as showing a higher degree of bisexual bonding and association than eastern chimpanzees, and eastern female chimpanzees (P. t. schweinfurthii) are thought to be more solitary than western female chimpanzees. However, reported comparisons in sociality currently depend on a small number of study groups, particularly in western chimpanzees, and variation in methods. The inclusion of additional communities and direct comparison using the same methods are essential to assess whether reported subspecies differences in sociality hold in this behaviorally heterogeneous species. We explored whether sociality differs between two communities of chimpanzees using the same motion‐triggered camera technology and definitions of social measures. We compare party size and composition (party type, sex ratio) between the western Gahtoy community in the Nimba Mountains (Guinea) and the eastern Waibira community in the Budongo Forest (Uganda). Once potential competition for resources such as food and mating opportunities were controlled for, subspecies did not substantially influence the number of individuals in a party. We found a higher sex‐ratio, indicating more males in a party, in Waibira; this pattern was driven by a greater likelihood in Gahtoy to be in all‐female parties. This finding is the opposite of what was expected for eastern chimpanzees, where female‐only parties are predicted to be more common. Our results highlight the flexibility in chimpanzee sociality, and caution against subspecies level generalizations. Research highlights: Party size in western and eastern chimpanzees did not differ between our two study communities suggesting that the number of individuals in a party is shaped by similar socio‐ecological pressures.In our sample, eastern chimpanzees were found to have more males in a party compared to western chimpanzees, contrary to the expectation of more female‐only parties in eastern compared to western chimpanzees.Our findings highlight the flexibility in chimpanzee grouping patterns and caution against subspecies level generalizations from limited data points and/or heterogeneous methods. [ABSTRACT FROM AUTHOR]

The significance of aquatic food resources for hominins is poorly understood, despite evidence of consumption as early as 1.95 million years ago (Ma). Here we present the first evidence of a non-human ape habitually catching and consuming aquatic crabs. Chimpanzees (Pan troglodytes verus) in the rainforest of the Nimba Mountains (Guinea) consumed freshwater crabs year-round, irrespective of rainfall or ripe fruit availability. Parties of females and offspring fished for crabs more than predicted and for longer durations than adult males. Across months, crab-fishing was negatively correlated with ant-dipping, suggesting a similar nutritional role. These findings contribute to our understanding of aquatic faunivory among hominins. First, aquatic faunivory can occur in closed forests in addition to open wetlands. Second, aquatic fauna could have been a staple part of some hominin diets, rather than merely a fallback food. Third, the habitual consumption of aquatic fauna could have been especially important for females and their immature offspring. In addition to providing small amounts of essential fatty acids, crabs might also be eaten for their micronutrients such as sodium and calcium, especially by females and young individuals who may have limited access to meat. [ABSTRACT FROM AUTHOR]

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]

Reconciliation is a conflict resolution mechanism that is common to many gregarious species with individualized societies. Reconciliation repairs the damaged relationship between the opponents and decreases postconflict (PC) anxiety. The “integrated hypothesis” links the quality of the opponents' relationship to PC anxiety, since it proposes that conflicts among partners with high relationship quality will yield high levels of PC anxiety, which in turn will lead to an increased likelihood of reconciliation. We tested the integrated hypothesis in captive chimpanzees (Pan troglodytes) in the Arnhem Zoo, The Netherlands. We applied the standard PC/matched control (MC) method. Our results mostly support the integrated hypothesis, in that more valuable and compatible partners (i.e., males and frequent groomers) reconciled more often than less valuable and weakly compatible partners (i.e., females and infrequent groomers). In addition, PC anxiety was higher after conflicts among males than among females. Emotional arousal thus appears to be a mediator facilitating reconciliation. However, in contrast to the predictions derived from the integrated hypothesis, PC anxiety appeared only in aggressees, and not in aggressors, of conflicts. This suggests that while relationship quality determines PC anxiety, it is dependent on the role of the participants in the conflict. Am J Primatol 69:1–15, 2007. © 2006 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Behavioural diversity in the predation pattern of army ants (Dorylus spp.) by different populations of wild chimpanzees, Pan troglodytes, has been proposed to reflect different cultural traditions. Chimpanzees use either stick tools (known as ant dipping) or simply their hands to prey on two groups of army ants (epigaeic and intermediate species). A recent analysis has shown that, contrary to the cultural hypothesis, the tool length and associated harvesting technique used by chimpanzees in different populations is to a large extent influenced by characteristics of the ants themselves. However, in line with the cultural hypothesis, chimpanzees at two long-term study sites in West Africa (Bossou, Guinea, and Taï National Park, Côte d''Ivoire) prey on the same five army ant species but adopt different strategies to do so. We conducted controlled human simulations of ant dipping and an ant survey at these two sites to evaluate alternative ecological explanations related to ant behaviour and ecology that could account for the observed differences in chimpanzee predation behaviour. Ant speed explained differences in tool length within Bossou but not between Bossou and Taï. Our results do not support an ecological basis underlying the lack of dipping at ant trails in Taï chimpanzees. Finally, neither ant aggressiveness (measured as speed and persistence) nor yield when using tools could explain why, unlike Bossou chimpanzees, Taï chimpanzees do not use tools to harvest epigaeic species. We conclude that an interaction of cultural and ecological factors shapes the differences in army ant predation between Taï and Bossou chimpanzees. [Copyright &y& Elsevier]