Abstract
Among mammals, individuals form strong social bonds preferentially with their kin. Differences in these relationships are linked to differential kin availability due to sex-specific dispersal patterns, but there is some indication that differential bonding among sexes already occurs prior to maturation. However, little is known about how these patterns arise during individual development. Here we investigated sex differences in the development of mother-offspring bonds in rhesus macaques (Macaca mulatta). Our results revealed that mothers showed sex-biased bonding toward their offspring. Sons had a distinctly higher probability of receiving aggression from their mothers than did daughters in the first year of life, while no differences were found with respect to affiliative interactions. After the first year, probabilities of all affiliative and aggressive behaviours investigated were higher for daughters than for sons, although generally declining. Furthermore, sons spending less time with their mother and receiving more maternal aggression tended to disperse earlier. The results of our study suggest that mothers influence their bonding strength with offspring by interacting less affiliative with sons than daughters.
Highlights
Many mammal species live in social groups that are characterized by differentiated social relationships among individual group members [1]
The study was performed on the rhesus macaque population of Cayo Santiago (CS, 18°90N, 65° 440W), a 15.2 ha island approximately 1 km from Puerto Rico (USA), which is managed by the Caribbean Primate Research Center (CPRC)
Sons received maternal aggression predominantly within the first year of life (i.e. 62% of all aggression observed toward sons over the four-year study period occurred within their first year of life), and mainly occurred spontaneously (69%), i.e. without previous interaction, including nursing
Summary
Many mammal species live in social groups that are characterized by differentiated social relationships among individual group members [1]. Maternal relatedness among the philopatric sex seems to be a driver of strong and long-lasting social bonds [4,5,6]. These findings led to the assumption that the philopatric sex should form more and stronger social bonds than the dispersing sex [7,8,9]. There is evidence that the members of the dispersing sex show less social bonding after they have left their natal group (e.g. males [10], females [11]). It has been reported that even in the PLOS ONE | DOI:10.1371/journal.pone.0154845 May 18, 2016
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