Please cite this article in press as: Biondo, C., et al., Social structure of collared peccaries (Pecari tajacu): Does relatedness matter? Behav. Process. (2014), http://dx.doi.org/10.1016/j.beproc.2014.08.018 ARTICLE IN PRESS G Model BEPROC-2886; No. of Pages 9 Behavioural Processes xxx (2014) xxx–xxx Contents lists available at ScienceDirect Behavioural Processes jo ur nal homep ag e: www.elsevier.com/locate/behavproc Social structure of collared peccaries (Pecari tajacu): Does relatedness matter? Cibele Biondo a,b,∗ , Patrícia Izar a , Cristina Y. Miyaki b , Vera S.R. Bussab a a Departamento de Psicologia Experimental, Instituto de Psicologia, Universidade de São Paulo, Av. Prof. Mello Moraes 1721, São Paulo, SP 05508-030, Brazil b Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo, Rua do Matão 277, São Paulo, SP 05508-090, Brazil a r t i c l e i n f o Article history: Available online xxx Keywords: Kinship Microsatellite Spatial association Tayassuidae a b s t r a c t Relatedness is considered an important factor in shaping social structure as the association among kin might facilitate cooperation via inclusive fitness benefits. We addressed here the influence of relatedness on the social structure of a Neotropical ungulate, the collared peccary (Pecari tajacu). As peccaries are highly social and cooperative, live in stable cohesive herds and show certain degree of female philopatry and high mean relatedness within herds, we hypothesized that kin would be spatially closer and display more amicable and less agonistic interactions than non-kin. We recorded spatial association patterns and rates of interactions of two captive groups. Pairwise relatedness was calculated based on microsatellite data. As predicted, we found that kin were spatially closer than non-kin, which suggests that relatedness is a good predictor of spatial association in peccaries. However, relatedness did not predict the rates of social interactions. Although our results indirectly indicate some role of sex, age and familiarity, further studies are needed to clarify the factors that shape the rates of interactions in collared peccaries. This article is part of a Special Issue entitled: Neotropical Behaviour. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Social structure is defined as the network of inter-individual relationships established among members of a given animal group (Hinde, 1976). This network is dynamic and can change over time under the influence of many factors. Some factors represent eco- logical constraints such as availability of resources and predation pressure (Kappeler and van Schaik, 2002). Others are related to group composition, including kinship, familiarity, age, sex and social status (Kappeler et al., 2013). Knowledge about such factors and how they affect the establishment of relationships is necessary to fully understand the social structure of a group of animals. Kin relationships have been proposed to be important in shaping social structure (Clutton-Brock and Janson, 2012). The association among kin might facilitate cooperation, and is predicted to be favored by natural selection when the inclusive benefits of cooper- ation outweigh the costs of sociality (Hamilton, 1964). This could be particularly true in many mammalian societies where relatives ∗ Corresponding author. Present address: Centro de Ciências Naturais e Humanas (CCNH), Universidade Federal do ABC (UFABC), Rua São Paulo s/n ◦ , São Bernardo do Campo, SP 09606-070, Brazil. Tel.: +55 11 2320 6307. E-mail addresses: cibele.biondo@ufabc.edu.br, cibelebiondo@yahoo.com.br (C. Biondo). live together as a consequence of female philopatry (Silk, 2007). If this was the case, we could expect that mammals prefer close rela- tives as social partners. In fact, there is empirical evidence both for and against that hypothesis. In rhesus monkeys (Macaca mulatta), for example, maternal and paternal half-sisters are spatially closer, present higher frequency of grooming than unrelated females, and help each other during agonistic interactions with other individ- uals (Schülke et al., 2013; Widdig et al., 2001). In southern flying squirrels (Glaucomys volans), on the other hand, prior familiarity, but not relatedness, predicts the patterns of associations between individuals (Garroway et al., 2013), which indicates that other fac- tors could also be important. In yellow-bellied marmot (Marmota flaviventris), in addition to kinship, age plays a significant role in social structure, with individuals of the same age class displaying more affiliative interactions among them than those of different age classes (Wey and Blumstein, 2010). Here, we studied the social structure of an ungulate species, the collared peccary, Pecari tajacu. This species is the most widespread of the Neotropical family Tayassuidae. This family together with the Old World family Suidae forms the suborder Suina (Agnarsson and May-Collado, 2008). The studies that addressed the role of relatedness in the social structure of Suina are focused in Suidae species, mainly in domestic pig and wild boars (both Sus scrofa). These studies have shown little or no influence of relatedness in the associations (Durrell et al., 2004; Iacolina et al., 2009) and rates http://dx.doi.org/10.1016/j.beproc.2014.08.018 0376-6357/© 2014 Elsevier B.V. All rights reserved.