INFLUENCE OF FATHER AND PREGNANCY ON MATERNAL-CARE IN RED-BACKED VOLES

Presence of fathers and concurrent pregnancy have been shown to influe nce 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 influ enced maternal behavior. Experiments were conducted in a seminatural e nvironment with observations occurring every other day from day 1 to d ay 20 of Life of the young. Although male and female red-backed voles always built and maintained separate nests, there was substantial vari ation among females in their response to fathers in the vicinity of th e natal nest. Whereas some females permitted fathers in the nest soon after birth, others reacted aggressively and prevented fathers from in teracting with young throughout most of the preweaning period. Such va riation in behavior of females appeared responsible, at least in part, for variation among individual males in level of paternal care. Overa ll, females caring for young in the presence of fathers spent less tim e nursing and groomed their young less frequently than did females rea ring young in the absence of fathers. Lower maternal care in the fathe r present condition may reflect reduced maternal workload in the pairs in which males spent considerable time in the nest with young or disr uption caused by presence of males in the pairs in which females aggre ssively excluded males from the natal nest. The maternal behavior of p regnant females did not differ from that of nonpregnant females.