DOI: 10.5061/dryad.j0zpc86bq
title: Bonds of bros and brothers: Kinship and social bonding in post-dispersal male macaques

description: Group-living animals often maintain a few very close affiliative
 relationships – social bonds – that can buffer them against many of the
 inevitable costs of gregariousness. Kinship plays a central role in the
 development of such social bonds. The bulk of research on kin biases in
 sociality has focused on philopatric females, who typically live in deeply
 kin-structured systems, with matrilineal dominance rank inheritance and
 life-long familiarity between kin. Closely related males, in contrast, are
 usually not close in rank or familiar, which offers the opportunity to
 test the importance of kinship per se in the formation of social bonds. So
 far, however, kin biases in male social bonding have only been tested in
 philopatric males, where familiarity remains a confounding factor. Here,
 we studied bonds between male Assamese macaques, a species in which males
 disperse from their natal groups, and in which male bonds are known to
 affect fitness. Combining extensive behavioural data on 43 adult males
 over a 10-year period with DNA microsatellite relatedness analyses, we
 find that post-dispersal males form stronger relationships with the few
 close kin available in the group than with the average non-kin. However,
 males form the majority of their bonds with non-kin, and may choose
 non-kin over available close kin to bond with. Our results show that
 kinship facilitates bond formation, but is not a prerequisite for it,
 which suggests that strong bonds are not restricted to kin in male mammals
 and that animals cooperate for both direct and indirect fitness benefits.
description: This data is part of a long-term research project on a population
 of fully habituated Assamese macaques ranging in their natural habitat in
 the Phu Khieo Wildlife Sanctuary (PKWS) in north-eastern Thailand. We
 studied one group from 2006 to 2012, 3 groups from 2012 to 2014 and 4
 groups from 2014 to 2017 on a total of 43 adult males. The study period
 was divided into stable periods (6-8 per group), defined as periods during
 which adult male group composition did not change. Observational data were
 collected almost daily, from dawn to dusk, using 20 to 40 minutes
 continuous focal animal sampling. During these protocols, frequencies and
 durations of affiliative behaviours (i.e. grooming, body contact and
 proximity within a 1.5 m radius) were recorded, as well as agonistic
 interactions. To measure social relationship strength, we used the dynamic
 dyadic sociality index (DDSI); dominance ranks were calculated based on
 the Elo-rating method. To assess relatedness we genotyped all 136 adult
 individuals of the population at 17 microsatellite loci and one mtDNA
 locus (details see manuscript). We estimated relatedness using the triadic
 maximum likelihood estimator, and assigned dyads with r &gt; 0.25 to
 close kin and dyads with r &lt; 0.125 to non-kin. Our research was
 completely non-invasive and followed the ASAB/ABS Guidelines for the Use
 of Animals in Research. Data collection and export of samples were
 authorized by the Department of National Parks, Wildlife and Plant
 Conservation (DNP) and the National Research Council of Thailand (NRCT)
 with a benefit sharing agreement (permit numbers: 0004.3/3618,
 0002.3/2647, 0002/17, 0002/2424, 0002/470).