Paternal experience and stress responses in California mice (Peromyscus californicus).

Paternal behavior greatly affects the survival, social development, and cognitive development of infants. Nevertheless, little research has been done to assess how paternal experience modifies the behavioral characteristics of fathers, including fear and stress responses to a novel environment. We investigated long-term behavioral and physiologic effects of parental experience in mice (Peromyscus californicus) and how this response activates the hypothalamic-pituitary-adrenal axis (as measured by corticosterone and dehydroepiandrosterone [DHEA] levels) and interacts with anxiety-related behaviors. Three groups of adult males were tested--fathers exposed to pups, virgins exposed to pups, and virgins never exposed to pups--in 2 environments designed to elicit anxiety response: an open field with a novel object placed in the center and a closed cage containing a sample of a component of fox feces. Behavioral responses were measured by using traditional methods (duration and frequency) and behavioral-chain sequences. Results indicated that paternal experience significantly modifies a male mouse's behavioral and physiologic responses to stress-provoking stimuli. Compared with inexperienced male mice, experienced male mice had a significant decrease in the occurrence of incomplete behavioral chains during the exposure to the novel object, an index of reduced stress. Further, even moderate pup exposure induced behavioral modifications in virgin male mice. These behavioral responses were correlated with changes in corticosterone and DHEA levels. Together, these data provide evidence that interactions between male mice and offspring may have mutually beneficial long-term behavioral and physiologic effects.