Opposite effects of male and female helpers on social tolerance and proactive prosociality in callitrichid family groups.

Judith M Burkart

doi:10.1038/srep09622

Abstract

Across a broad variety of primate species (including lemurs, New World monkeys, Old World monkeys, and apes), proactive prosociality and social tolerance are linked to allomaternal care, reaching the highest levels in the cooperatively breeding callitrichid monkeys and humans. However, considerable variation exists within callitrichids, and the aim of this study was to identify factors that explain this variation. Male and female callitrichids pursue different reproductive strategies, leading males to play a more prominent role in allomothering. We thus hypothesised that prosociality and tolerance may be affected by group composition and sex differences. We analysed social tolerance and proactive prosociality data in 49 common marmosets and found that the number of female helpers in a group was negatively correlated with group-level prosociality and tolerance. At the individual level, rearing experience or age enhanced prosociality in male, but not in female helpers. These findings are consistent with the more ambivalent role of female helpers in infant rearing. Adding data from 5 cotton-top and 5 lion tamarins strengthened this pattern. The same factor which explains variation in prosociality and tolerance across primate species, i.e. allomaternal care, is therefore also linked to variation within common marmosets, and presumably callitrichid monkeys in general.

Highlights

Opposite effects of male and female helpers on social tolerance and proactive prosociality in callitrichid family groups
The aim of this study was to evaluate whether the same factor that explains variation in social tolerance and proactive prosociality in a provisioning experiment across a large number of primate species, i.e. the amount of allomaternal care, explains variation within the cooperatively breeding common marmosets
The aim of this study was to evaluate whether the same factor that explains variation in social tolerance and proactive prosociality across a large number of primate species, i.e. the amount of allomaternal care, explains variation within common marmoset monkeys

Summary

Introduction

Opposite effects of male and female helpers on social tolerance and proactive prosociality in callitrichid family groups. Recent comparative results based on a single, standardized experimental procedure that provides comparable data, the group service paradigm, suggest that the elevated levels of social tolerance and prosociality in callitrichid monkeys are linked to their cooperative breeding system, where non-mothers provide a significant amount of infant care (i.e. allomaternal care). These data from a large number of primate species including lemurs, New World monkeys, Old World monkey and apes showed that the extent of allomaternal care predicts the extent of social tolerance and proactive prosociality[7]. If variation in social tolerance and proactive prosociality among callitrichids is driven by the same factor as interspecific variation among primates in general, i.e. allomaternal care, we should expect distinct patterns with regard to the presence of infants in a group and with regard to group composition

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