Heterogeneity in resource competition covaries with individual variation in long-term social relationships

Resource competition among conspecifics is central to social evolution, as
it serves as one of the primary selective pressures of group living. This
is because the degree of competition for resources impacts the costs and
benefits of social interactions. Despite this, how heterogeneity in
resource competition drives variation in the type and quantity of
long-term social relationships individuals foster has been overlooked. By
measuring male mating competition and female foraging competition in a
highly social, long-lived mammal, we demonstrate that individual variation
in long-term intrasexual social relationships covaries with preferred
habitat and experienced resource competition, and this effect differs
based on the sex of the individual. Specifically, greater resource
competition resulted in fewer social preferences, but the magnitude of the
effect varied by both habitat and sex, whereas for social avoidances, both
the directionality and magnitude of the effect of resource competition
varied by habitat and sex. Together our work shows how fine-scale
variation in individual socioecological niches (i.e., unique physical and
social environments) can drive extensive variation in individual social
behavior (here long-term relationships) within a population, thereby
broadening current theories of social evolution.