Influence of photoperiod and social environment on sexual maturation in female deer mice (Peromyscus maniculatus bairdii).

Female deer mice (Peromyscus maniculatus) were reared on either a long photoperiod (15:9 hr light/dark) or on short days (8:16 hr light/dark) from birth. Beginning at weaning, females were housed with an adult male, with an adult female, or in social isolation. In the first experiment, vaginas opened more slowly in females on short days than in those on long days. Vaginal introitus was also retarded in females reared with an adult female in comparison with females reared in isolation. When examined at 37 days of age, females reared with an adult male had larger uteri than those reared alone; uteri were also larger in long-day than in short-day females. In Experiment 2, females were killed at 30 days of age; again, uterine growth was stimulated by exposure of young females to either long days or an adult male. As was previously demonstrated for male deer mice, sexual maturation in females is regulated by photoperiod and social cues. Heterospecific social stimuli accelerate maturation in individuals that otherwise would be inhibited by having been reared on a short photoperiod.