Infants Receive More Care by Harassing Matings in a Multi-Level Primate Society

TL;DR

Infant Sichuan snub-nosed monkeys harass their mothers during mating to receive more care, suggesting a strategy to gain parental attention.

Contribution

This study identifies infant harassment of maternal mating as a behavior linked to increased maternal care in a multilevel primate society.

Findings

Infants harassed their mothers more during mating than non-mothers, leading to increased maternal care.

Mothers responded to harassment with increased caretaking, while non-mothers responded with aggression.

Infant harassment of matings correlates with receiving more care and facing more aggression.

Abstract

The aims of this study were to assess the motivation underlying harassment of adult matings by infants in a multilevel social primate, namely wild (provisioned) Sichuan snub-nosed monkeys, and to describe and quantify the reactions of harassed adults to infant harassment. Infants more frequently harassed sexual activities of their mothers than non-mothers, leading to them receiving more care from their mothers; non-mothers were more likely to respond to infant harassment with aggression. These findings can be taken as providing indirect support for parent–infant conflict theory in as much as infant harassment of their mother’s sexual activity was effective in securing more maternal care. Future work on parent–infant conflict should incorporate behavioral, physiological, and reproductive measures, including pregnancy onset and inter-birth intervals.

To better understand the motivation underlying harassment of adult matings by infants, we studied infant harassment behaviors in a multilevel social primate, wild (provisioned) Sichuan snub-nosed monkeys (Rhinopithecus roxellana). Two harassment patterns were identified: care-seeking and sociable. Infants showed more frequent harassment in response to sexual activities of their mothers than non-mothers, with more care-seeking harassment directed to their mothers. The responses of mothers and non-mothers to infant harassment were different, with the former showing increased caretaking of their infants. Infants harassing non-mothers were more likely to receive aggression from the latter than infants harassing their own mothers. Overall, the more frequently infants harassed matings, the more care they received and the more attacks they received. We conclude that in Sichuan snub-nosed monkeys, infant harassment of their mother’s sexual activity is an effective behavioral tactic to receive more maternal care. It can therefore be interpreted as indirect support for the parent–offspring conflict hypothesis.

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