DOI: 10.5061/dryad.63xsj3tzf
title: Female Assamese macaques bias their affiliation to paternal and maternal kin

description: Forming strong social bonds can lead to higher reproductive success,
 increased longevity and/or increased infant survival in several mammal
 species. Given these adaptive benefits, understanding what determines
 partner preferences in social bonding is important. Maternal relatedness
 strongly predicts partner preference across many mammalian taxa. The role
 of paternal relatedness, however, has received relatively little
 attention, even though paternal and maternal kin share the same number of
 genes, and theoretically similar preferences would therefore be expected
 for paternal kin. Here, we investigate the role of maternal and paternal
 relatedness in female affiliation in Assamese macaques (Macaca
 assamensis), a species characterized by a relatively low male reproductive
 skew. We studied a wild population under natural conditions using
 extensive behavioral data and relatedness analyses based on pedigree
 reconstruction. We found stronger affiliative relationships and more time
 spent grooming between maternal kin and paternal half-sisters compared to
 non-kin, with no preference of maternal over paternal kin. Paternally
 related and non-related dyads did not form stronger relationships when
 they had less close maternal kin available, but we would need a bigger
 sample size to confirm this. As expected given the low reproductive skew,
 affiliative relationships between paternal half-sisters closer in age were
 not stronger than between paternal half-sisters with larger age
 differences, suggesting that the kin bias towards paternal kin was not
 mediated by age similarity. An alternative way through which paternal kin
 could get familiarized is mother- and/or father-mediated familiarity.
description: This study is part of a long-term research project on
 a population of Assamese macaques at the Phu Khieo Wildlife Sanctuary. All
 individuals could be reliably identified based on natural variation in
 appearance. We collected data on one group in 2007/2008 and 2010/2011, on
 two groups in 2013/2014, and on four groups in 2015/2016 and 2016/2017.
 This study focused on
 adult females (n=59), with females defined as adult in the mating season
 of their first conception. For 25 of these females the mother and exact
 age are known from direct observation. The other 34 females were already
 present in the population when the project started in 2006, so no
 information on their mother was available and age was estimated based on
 morphology and behavior. To collect observational data
 we followed the study groups from dawn to dusk, from sleep tree to sleep
 tree. During 40 minutes continuous focal animal observations, we recorded
 frequencies and durations along with actor and receiver of affiliative
 behaviors (proximity, body contact and grooming). To measure the strength
 of affiliative relationships among adult females, we used a modified
 dyadic composite sociality index based on the frequency and duration of
 proximity, body contact and grooming. To assess relatedness and assign
 dyads to kin classes 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 to kin classes based on parentage analyses
 using the softwares Colony and Cervus. This study was conducted completely
 non-invasively and adhered to the ASAB/ABS Guidelines for the Use of
 Animals in Research. The Department of National Parks, Wildlife and Plant
 Conservation (DNP) and the National Research Council of Thailand (NRCT)
 authorized data collection and export of samples with a benefit sharing
 agreement (permit numbers: 0004.3/3618, 0002.3/2647, 0002/17, 0002/2424,
 0002/470).