How chimpanzees (Pan troglodytes) share the spoils with collaborators and bystanders

Abstract

Chimpanzees hunt cooperatively in the wild, but the factors influencing food sharing after the hunt are not well understood. In an experimental study, groups of three captive chimpanzees obtained a monopolizable food resource, either via two individuals cooperating (with the third as bystander) or via one individual acting alone alongside two bystanders. The individual that obtained the resource first retained most of the food but the other two individuals attempted to obtain food from the "captor" by begging. We found the main predictor of the overall amount of food obtained by bystanders was proximity to the food at the moment it was obtained by the captor. Whether or not an individual had cooperated to obtain the food had no effect. Interestingly, however, cooperators begged more from captors than did bystanders, suggesting that they were more motivated or had a greater expectation to obtain food. These results suggest that while chimpanzee captors in cooperative hunting may not reward cooperative participation directly, cooperators may influence sharing behavior through increased begging.

Azure-winged magpies’ decisions to share food are contingent on the presence or absence of food for the recipient

“…The group members begged more in the condition in which they had no access to mealworms, and the subject birds were more likely to share their mealworms when their conspecifics were begging. This finding is similar to findings in chimpanzees that also showed that those that don't have access to a specific food item beg frantically and those that have the food item seem to react with sharing 24,43,45 , although there are also reports that show negative effects of requests on prosocial sharing in both chimpanzees and orangutans in a food-sharing task 47 and of attention-getting behavior in chimpanzees 46 .…”

“…In contrast, food-sharing among adults is relatively rare, although not absent. As with prosociality in general, recent studies have reported adult-adult food-sharing in our closest living relatives (bonobos even between groups 21 , but see 22 ; chimpanzees 22 – 24 , other nonhuman primates (reviewed in 25 ), other social mammals (e.g. vampire bats, Desmodus rotundus 26 ; killer whales, Orcinus orca 27 ) and several bird species 28 – 34 .…”

“…Partners may use begging or specific requests as cues to communicate their needs and/or desires. Findings on the mediating role of active requests of the recipients in chimpanzee prosociality, however, are rather inconsistent, with reports of positive effects on targeted helping 24 , 43 , 45 and negative effects on prosocial behavior in both a prosocial choice task 46 and a food-sharing task 47 . To examine whether prosocial food-sharing is motivated by sympathy, Liebal and colleagues 48 adapted an existing testing paradigm for children 49 , to investigate whether apes are more likely to help a conspecific after it was ‘harmed’.…”

Reduced risk-seeking in chimpanzees in a zero-outcome game

“…In captive settings, pairs of chimpanzees are willing to cooperate even when the distribution of rewards is unequal, i.e. when one partner gets more than the other [ 29 , 30 ]. Cooperation breaks down, however, if one partner can never profit [ 31 , 32 ].…”

Reduced risk-seeking in chimpanzees in a zero-outcome game

“…Also, in the social domain, investing in social partners may bear the risk of getting nothing if others do not reciprocate. In captive settings, pairs of chimpanzees are willing to cooperate even when the distribution of rewards is unequal, i.e., when one partner gets more than the other (29,30). Cooperation breaks down, however, if one partner can never profit (31,32).…”