Meeting Abstract
Although uniparental care of offspring is the rule among mammals, approximately 5% of species practice biparental care, in which both parents contribute to the rearing of their young. Males in some biparental species exhibit pronounced changes in their behavioral responses to infants during the transition to fatherhood. Such changes have been especially well studied in the monogamous, biparental California mouse (Peromyscus californicus). New fathers in this species undergo shifts in several neural, metabolic, morphological, and behavioral measures, which are likely mediated by hormonal changes occurring shortly before and after the birth of pups. For example, new fathers and nonbreeding males show differences in expression of hormone receptors and neuronal morphology within specific brain regions, as well as differences in body mass, organ masses, and behavioral responses to stressors. The stimuli eliciting such effects are not well understood but may include cohabitation with a female — especially a pregnant female — and exposure to pups. Paternal behavior can be modestly inhibited by acute exposure to stressors or stress-related hormones; however, exposure to chronic stressors does not markedly alter paternal care. At the level of inter-individual variation, few differences are seen among fathers, which consistently exhibit attraction and nurturance toward pups. Virgin males, in contrast, show pronounced differences in pup-directed behavior, ranging from caretaking to infanticide. The proximate bases of these differences are not clear, but previous exposure to pups enhances caretaking behavior in virgin males. Thus, variation in paternal responsiveness in California mice may result from both physiological and experiential factors. (Supported by NIH HD075021, NIH HD075021, and NSF IOS1256572.)
