Influence of father and pregnancy on maternal care in red-backed voles

Abstract

Presence of fathers and concurrent pregnancy have been shown to influence maternal behavior in rodents, but often are confounded in studies of species that mate during postpartum estrus. I examined parent-young interactions in red-backed voles (Clethrionomys gapperi) to document patterns of parental care in this species and to determine whether the separate factors of presence of father and concurrent pregnancy influenced maternal behavior. Experiments were conducted in a seminatural environment with observations occurring every other day from day 1 to day 20 of life of the young. Although male and female red-backed voles always built and maintained separate nests, there was substantial variation among females in their response to fathers in the vicinity of the natal nest. Whereas some females permitted fathers in the nest soon after birth, others reacted aggressively and prevented fathers from interacting with young throughout most of the preweaning period. Such variation in behavior of females appeared responsible, at least in part, for variation among individual males in level of paternal care. Overall, females caring for young in the presence of fathers spent less time nursing and groomed their young less frequently than did females rearing young in the absence of fathers. Lower maternal care in the father present condition may reflect reduced maternal workload in the pairs in which males spent considerable time in the nest with young or disruption caused by presence of males in the pairs in which females aggressively excluded males from the natal nest. The maternal behavior of pregnant females did not differ from that of nonpregnant females.