Feeding Competition and Patch Size in the Chimpanzee Species Pan Paniscus and Pan Troglodytes

Wrangham, Richard W.; White, Frances J.

doi:10.1163/156853988x00494

Cited by 171 publications

(55 citation statements)

References 19 publications

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“…To disentangle the effect of competition for early access with other chimpanzees at the sleeping site from that with other foraging species at the breakfast site, we needed to control for the effect of intragroup competition on departure time. Hence, we included the number of males in the group and the duration of breakfast feeding as an estimate of the amount of edible fruit (27) at the breakfast site, and their interaction, as control predictors in the model (Table 1). We expected that departure time would be earlier when the estimated amount of food was small, especially when the number of males at the nest was larger, reflecting increased intragroup competition for breakfast fruit.…”

Section: Resultsmentioning

confidence: 99%

Wild chimpanzees plan their breakfast time, type, and location

Janmaat

Polansky

Ban

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

146

141

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Not all tropical fruits are equally desired by rainforest foragers and some fruit trees get depleted more quickly and carry fruit for shorter periods than others. We investigated whether a ripe-fruit specialist, the chimpanzee (Pan troglodytes verus), arrived earlier at breakfast sites with very ephemeral and highly sought-after fruit, like figs, than sites with less ephemeral fruit that can be more predictably obtained throughout the entire day. We recorded when and where five adult female chimpanzees spent the night and acquired food for a total of 275 full days during three fruit-scarce periods in a West African tropical rainforest. We found that chimpanzees left their sleeping nests earlier (often before sunrise when the forest is still dark) when breakfasting on very ephemeral fruits, especially when they were farther away. Moreover, the females positioned their sleeping nests more in the direction of the next day's breakfast sites with ephemeral fruit compared with breakfast sites with other fruit. By analyzing departure times and nest positioning as a function of fruit type and location, while controlling for more parsimonious explanations, such as temperature, we found evidence that wild chimpanzees flexibly plan their breakfast time, type, and location after weighing multiple disparate pieces of information. Our study reveals a cognitive mechanism by which largebrained primates can buffer the effects of seasonal declines in food availability and increased interspecific competition to facilitate first access to nutritious food. We discuss the implications for theories on hominoid brain-size evolution.prospective cognition | flexible planning | ecological intelligence | interspecific competition | foraging strategies T hree decades ago, Katharine Milton hypothesized that the diversity of food and the manner in which it is distributed in space and time have been major selective forces in the development of advanced cerebral complexity (the ecological intelligence hypothesis) (1, 2). Positive associations between a variety of brain size measures and levels of frugivory (i.e., the dietary proportion of patchily distributed and ephemeral food) were found in primates (3, 4), bats, and rodents (5). However, the idea that body size evolves more rapidly than brain size, meaning the small relative brain size of folivores could be a nonequilibrial situation, kept scientists from interpreting these associations as clear support for Milton's hypothesis (6; but see also ref. 7). The ecological intelligence hypothesis was, however, retained as one of the four components of the technical intelligence hypothesis, developed to find evolutionary explanations of great apes' representational skills (6). It was renamed the "cognitive map hypothesis," which unintentionally focused attention solely on the complexity of the spatial mapping of food and largely ignored the potential difficulty of anticipating the time and duration that food is present.With recent comparative studies on brain size evolution, the role of the tempora...

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Section: Resultsmentioning

confidence: 99%

Wild chimpanzees plan their breakfast time, type, and location

Janmaat

Polansky

Ban

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

146

141

View full text Add to dashboard Cite

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“…One hypothesis is that different levels of scramble competition for food may account for this suite of changes (Wrangham 2000;Wrangham & Pilbeam 2001). For example, wild chimpanzees may face more competition for smaller, less abundant food patches than do bonobos (White & Wrangham 1988) and have less access to terrestrial herbaceous vegetation as fallback food (Malenky & Wrangham 1993). In terms of aggression, chimpanzees show more linear dominance hierarchies and more severe (and sometimes lethal) aggression than do bonobos (Kano 1992;Watts & Mitani 2001;Boesch et al 2002;Muller et al 2009).…”

Section: Discussionmentioning

confidence: 99%

Decision making across social contexts: competition increases preferences for risk in chimpanzees and bonobos

Rosati

Hare

2012

Animal Behaviour

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Context can have a powerful influence on decision-making strategies in humans. In particular, people sometimes shift their economic preferences depending on the broader social context, such as the presence of potential competitors or mating partners. Despite the important role of competition in primate conspecific interactions, as well as evidence that competitive social contexts impact primates' social cognitive skills, there has been little study of how social context influences the strategies that nonhumans show when making decisions about the value of resources. Here we investigate the impact of social context on preferences for risk (variability in payoffs) in our two closest phylogenetic relatives, chimpanzees, Pan troglodytes, and bonobos, Pan paniscus. In a first study, we examine the impact of competition on patterns of risky choice. In a second study, we examine whether a positive play context affects risky choices. We find that (1) apes are more likely to choose the risky option when making decisions in a competitive context; and (2) the play context did not influence their risk preferences. Overall these results suggest that some types of social contexts can shift patterns of decision making in nonhuman apes, much like in humans. Comparative studies of chimpanzees and bonobos can therefore help illuminate the evolutionary processes shaping human economic behaviour. . Understanding the role of social context in shaping decision-making strategies is particularly important for biologists and psychologists who are interested in understanding behaviour in the real world, as gregarious species like primates must constantly make value-based decisions in the company of others. While cooperation in nonhumans has received increasing attention, little comparative research has examined the role of social context in shaping decisions when an individual's payoffs do not directly depend on their partner's behaviour. In the current study we therefore examine the impact of social context on risk preferences in chimpanzees, Pan troglodytes, and bonobos, Pan paniscus, our closest phylogenetic relatives.Studies of social context and decision making in humans have generally been motivated by evolutionary hypotheses concerning how the presence or absence of certain social partners might alter how decision makers value resources. In one study, Wilson & Daly (2004) found that men who viewed images of attractive women had steeper temporal discounting rates, devaluing the future much more heavily than men who viewed unattractive women or cars. That is, looking at attractive women made men more impulsive or present oriented, possibly because the attractive women cued men into the possibility that current possession of goods could increase mating opportunities. Social context also modulates people's willingness to take economic risks (or accept variability in payoffs). For example, men became more likely to choose risky options when their choices were watched by an observer of equal status, compared to when relative status was ...

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“…In doing so, bonobos may avoid some of the risk incurred by chimpanzees in their frugivorous foraging. Bonobos may also have access to larger fruit patches, facing less competition within a given patch than chimpanzees (White & Wrangham 1988), potentially turning fruit patches into safer options as well. Furthermore, chimpanzees, unlike bonobos, hunt monkeys, requiring the investment of extensive time into a risky outcome (Gilby & Wrangham 2007).…”

Section: Introductionmentioning

confidence: 99%

A fruit in the hand or two in the bush? Divergent risk preferences in chimpanzees and bonobos

et al. 2008

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).Human and non-human animals tend to avoid risky prospects. If such patterns of economic choice are adaptive, risk preferences should reflect the typical decision-making environments faced by organisms. However, this approach has not been widely used to examine the risk sensitivity in closely related species with different ecologies. Here, we experimentally examined risk-sensitive behaviour in chimpanzees (Pan troglodytes) and bonobos (Pan paniscus), closely related species whose distinct ecologies are thought to be the major selective force shaping their unique behavioural repertoires. Because chimpanzees exploit riskier food sources in the wild, we predicted that they would exhibit greater tolerance for risk in choices about food. Results confirmed this prediction: chimpanzees significantly preferred the risky option, whereas bonobos preferred the fixed option. These results provide a relatively rare example of risk-prone behaviour in the context of gains and show how ecological pressures can sculpt economic decision making.

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Feeding Competition and Patch Size in the Chimpanzee Species Pan Paniscus and Pan Troglodytes

Cited by 171 publications

References 19 publications

Wild chimpanzees plan their breakfast time, type, and location

Wild chimpanzees plan their breakfast time, type, and location

Decision making across social contexts: competition increases preferences for risk in chimpanzees and bonobos

A fruit in the hand or two in the bush? Divergent risk preferences in chimpanzees and bonobos

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