The ties that bind: Maternal kin bias in a multilevel primate society despite natal dispersal by both sexes

Abstract

In many social animals, individuals derive fitness benefits from close social bonds, which are often formed among kin of the philopatric sex. Hamadryas baboons, however, exhibit a hierarchical, multilevel social system where both sexes disperse from their natal one-male-unit (OMU). Although this would seem to hinder maintenance of kin ties, both sexes appear largely philopatric at the higher order band and clan levels, possibly allowing for bonds with same sex kin by both males and females. In order to investigate the possibility of kin bonds in hamadryas baboons, we identified kin dyads in a band without known pedigree information using a large panel of genetic markers: 1 Y-linked, 4 X-linked, and 23 autosomal microsatellites and part of the mitochondrial hypervariable region I. With these data, we performed a kinship analysis while accounting for misclassification rates through simulations and determined kinship among two types of dyads: leader and follower males and female dyads within OMUs. Leader and follower males were maternal relatives more often than expected by chance, suggesting that kinship plays a role in the formation of these relationships. Moreover, maternal female relatives were found in the same OMU more often than expected by chance, indicating that females may be motivated to maintain post-dispersal contact with maternal female kin. Our results suggest that hamadryas baboons can recognize maternal kin and that kin selection has contributed to shaping their complex social system. This implies that an ancestral maternal kin bias has been retained in hamadryas society. Am. J. Primatol. 78:731-744, 2016. © 2016 Wiley Periodicals, Inc.

Strategies for determining kinship in wild populations using genetic data

“…; Städele et al. ). Using such an approach, low misclassification rates can be achieved with a relatively small set of loci.…”

“…3B). Cutoffs can be defined by systematically testing values which maximize the true classification rate and minimize the misclassification rate or can be empirically defined using data from dyads of known pedigree relationship or from relatives identified through pedigrees reconstructed after parentage analysis (Langergraber et al 2007;St€ adele et al 2016).…”

Does a trade‐off between fertility and predation risk explain social evolution in baboons?

“…Indeed, their patterns of fissioning are completely opposite: hamadryas harems fission to forage during the day and coalesce for safety at night, whereas gelada harems coalesce to forage during the day and fission to sleep at night. The only feature that is common to both species is the substructuring of groups into harems: in both species, groups of closely related females (Dunbar, 1984;Swedell, 2002;Johnson et al, 2014;Snyder-Mackler, Alberts & Bergman, 2014;St€ adele et al, 2016) are attached to a male rather than dispersing in small, unstable foraging parties, as happens in chimpanzees (Lehmann, Korstjens & Dunbar, 2007b), spider monkeys (Korstjens, Verhoeckx & Dunbar, 2006) and perhaps Guinea baboons (Patzelt et al, 2011) under similar circumstances. In both species, the substructuring is reinforced (more so in hamadryas, less successfully so in gelada) by male herding behaviour.…”

An information-theory approach to geometry for animal groups

“…First, we hypothesised social hierarchy to be an important factor in how animals choose their preferred location, with lower ranking individuals' location being more strongly determined by others' location than higher ranking ones. Second, we also hypothesised kinships to have an effect, albeit in the opposite direction (Städele, Pines, Swedell, & Vigilant, 2016), resulting in greater predictability of related than unrelated individuals. Third, we hypothesised sex to play a role, such that same-sex individuals determined each other's position to a stronger degree than opposite-sex individuals, following the idea of male-female role allocation in wolves (Mech, 1999).…”