Behavioural asymmetries and cohesive mother–offspring sociality in bushy-tailed wood rats

Abstract

Bushy-tailed wood rats (Neotoma cinerea) are usually confined to highly clumped resource patches (i.e., rock outcrops), and potentially compete for limited den sites within outcrops. Adults may breed on the same outcrop over several years, and philopatric yearlings usually breed in proximity to close kin. We investigated the influence of kinship and reproductive status on the nature and stability of wood rat sociality. Behavioural interactions among mother–offspring and adult female – nonkin dyads from the wild were quantified in a neutral arena during (i) the autumn when offspring were immature subadults, and (ii) the following spring, when all dyad members were reproductively active. Nonkin dyads were characterized almost entirely by agonistic behaviour. Virtually all amicable behaviour was directed toward close kin, and most interactions among kin dyads were amicable. Further, these strong kin-based behavioural asymmetries did not differ between the autumn and the subsequent breeding season, and could not be explained by postweaning familiarity (i.e., residency on a common habitat patch) alone. Wood rat sociality appears to be characterized by two elements: (i) divisive agonism directed toward nonkin, and (ii) stable, cohesive relationships among close kin (mother–offspring). Possible causes and consequences of sociality in bushy-tailed wood rats are discussed.