Wild Vervet Monkeys Trade Tolerance and Specific Coalitionary Support for Grooming in Experimentally Induced Conflicts

Abstract

Grooming is a key social behavior in many primate species. Research has focused on three important aspects: the short- and long-term trading patterns of grooming for itself and/or for other commodities like tolerance or coalitionary support, the issue of whether exchanges are a convincing example for reciprocity, and what decision rules underlie trading. These issues remain largely unresolved due to the correlative nature of observational studies and the rarity of experimental studies. Here, we present a new experimental paradigm to address these questions in wild vervet monkeys (Chlorocebus pygerythrus). Adult females were first trained to approach a personal box, identifiable by unique color patterns, to access high-quality food. During the experiments, two boxes were placed next to each other to induce conflict through forced proximity. We found that while dominants were generally more tolerant toward bonded individuals, recent grooming increased tolerance independently of relationship quality. The latter result shows that vervet monkeys traded grooming for short-term tolerance, where dominants used a direct-reciprocity decision rule. In contrast, females invariably supported the higher-ranking opponent in a conflict, independently of who was the recent grooming partner. Nevertheless, recent grooming increased the probability that a female supported the partner during conflicts with a low-ranking third party. Thus, females' decisions about coalitionary support seem to integrate information about the current social hierarchy with recent grooming events. In conclusion, decision rules underlying trading of grooming for other commodities involve a variety of timescales and factors.

Interindividual differences in neonatal sociality and emotionality predict juvenile social status in rhesus monkeys

“…Neonatal imitation may reflect ingrained predispositions for advanced social skills (Kaburu et al., ; Paukner et al., ; Simpson, Murray, et al., ; Simpson et al., ). The finding that imitators attained higher social status suggests that these individuals may have advanced social competency in other regards (e.g., aggression, coalitions, play; Bissonnette et al., ; Borgeaud & Bshary, ), consistent with previous reports (Kaburu et al., ; Paukner et al., ; Simpson et al., ), at least up until 1 year of age. Our study extends these findings into juvenility and encompasses one of the most important social characteristics of rhesus monkeys: social status.…”

The effect of social and ecological factors on the time budget of wild vervet monkeys

“…Since females and their kin form the social core of the group, such sex differences have been found in most matriarchal primates’ species (Hemelrijk & Luteijn, ; Sterck et al, ; Wrangham, ). Besides its hygienic function, grooming is used to create and maintain social bonds between group members (Sade, ), decrease stress, which could be the result of group competition (Keverne et al, ; Schino et al, ), and promote cooperation (Borgeaud & Bshary, ). Females spent less time socializing during the winter season, while males spent more time socializing during the scarce season.…”

The magnitude of innovation and its evolution in social animals

“…The earliest documentation of patents and copyrights does not date very far in our history [46], but royalties do not necessarily require formal institutions to exist; trading in information for goods was likely a feature of human societies early on, and can be tied to our species' tendency to cooperate with non-kin [47]. Other animals do engage in simple forms of trade, perhaps the best-studied being the trade in grooming in exchange for dominant tolerance [48], infant handling [49] or mating [50]. However, in non-humans, there is little evidence for any trade in information that innovators would stand to gain from.…”