Little is known about sex differences in parental behavior of biparental mammals and if mates in such species coordinate care of young. We studied parental care displayed by prairie voles (Microtus ochrogaster) under seminatural laboratory conditions during the first 3 d of life of their offspring. Through direct observations and videotaping, we monitored members of male-female pairs to determine if sex differences in early parental behavior exist and if mothers and fathers coordinate visits to the nest. To assess the impact of fathers on survival of pups and behavior of mothers, we also examined parental care displayed by single females toward their young. Male and female members of breeding pairs differed dramatically in degree of parental care. Females spent more time in the nest with young and licked them more frequently than did males. Additionally, females maintained the nest more frequently than did males, whereas they maintained runways less frequently. Although coordination of visits to the nest was not perfect between members of pairs, pups of pairs were left alone for less time than were pups of single females. Parental behavior displayed by paired and single females did not differ, nor did survival of their young to day 3 or 15. We suggest that provision of ample space and cover to vole parents rearing young in captivity promotes expression of sex differences in parental behavior, but that even seminatural conditions are not sufficient to yield benefits of father presence to survival of young. Under more challenging conditions, such as cold temperatures or presence of predators, benefits of father presence might emerge.