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

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.