Spatial proximity and dyadic social relationships affect ungulate behavioral synchrony

Collective group decisions are important for the survival and reproduction of social mammals, with inter-individual interactions often driving group-level emergent behavior. Activity synchronization is an important collective behavior, with differences in nutritional requirements leading to foraging asynchrony. Individual variation between animals (such as sex or social relationships) are predicted to affect ungulate synchronization and spatial proximity, with between-sex differences consequently influencing sexual segregation evolution in ungulates. Although investigated independently, the relative roles of sex, sociality and proximity in synchronization are rarely investigated concurrently, especially in regards to affiliative relationships. Asynchrony influences fission-fusion dynamics and social segregation, but little is known how short-term changes in synchrony affects fission. Using a mixed-sex group of feral cattle (Bos taurus), we evaluated the supporting evidence for several predictions arising from the current understanding of synchronization in ungulates. We investigated if sex and social relationships (dominance and affiliation) affected foraging, behavioral synchrony and proximity. We also investigated whether group synchrony affected short-term changes in group size (fission events). We found that same-sex dyads were more likely to be synchronized than mixed-sex dyads, but differences in dominance and affiliation did not affect dyadic synchrony. Focal animals were more synchronized with closest neighbors than with another randomly selected conspecific. Reduction in group size was more likely when group synchrony was lower, highlighting the importance of asynchrony in temporary movement decisions. Inter-individual differences can explain variation in collective behavior, with synchronization being biased towards certain individuals by favoring animals in close spatial proximity and those of the same-sex. LAY SUMMARYIn ungulates, differences in energetic requirements lead to variation in activity, resulting in social and sexual segregation. However, sex, social relationships and spatial proximity are rarely investigated concurrently in relation to synchrony. We investigated synchronization and fission in a feral ungulate relative to individual differences in social relationship and proximity. Sex and proximity affected synchrony and fission events were more likely when synchrony was lower, highlighting the underlying processes in the evolution of sexual segregation.