Genetic relatedness does not predict racoon social network structure

Social assortativity, preferentially associating with certain individuals, is a widespread behaviour among a diverse range of taxa. Animals often choose to associate with other individuals based on characteristics such as sex, age, body size, rank and genetic relatedness. These preferences can scale up to shape the overall social structure of an animal group or population. We investigated possible factors that might shape the social network structure of common racoons, Procyon lotor, in a high-density urban population in Cook County, Illinois, U.S.A. Racoon associations were recorded using proximity detecting radiocollars that recorded when individuals came within 1–1.5 m of each other. In addition, dyadic measures of home range overlap and genetic relatedness were calculated for all individuals included in our study. We used multiple regression quadratic assignment procedures to determine what factors influenced the structure of racoon association networks. The only variable that positively influenced racoon social structure was male–male homophily, which is consistent with previous studies that documented frequent social interactions between adult male racoons. Genetic relatedness had no effect on racoon social networks and there was no evidence that males or females preferentially associated with close relatives, despite the presence of kin in the population. This pattern, that kinship does not play a significant role in shaping social structure, is strikingly unusual among mammals and is not consistent with many socioecological models. Although racoon individuals showed strong social partner preferences, it is unclear what factors drove these choices. This unpredictability in partner choice shaped the structure of the racoon social networks and has important implications for disease transfer in this widespread animal vector.