Effects of parental status on male body mass in the monogamous, biparental California mouse

Maternal care has significant physiological and morphological consequences for mammalian mothers. In contrast, little is known of the consequences of paternal care for mammalian fathers that help to rear offspring. We aimed to determine whether fathers in a biparental mammalian species, the California mouse (Peromyscus californicus), undergo systematic changes in body mass during reproduction and, if so, whether these changes are due to cohabitation with a female with a pregnant female specifically, and/or with pups. We compared body masses of experienced and first-time fathers across the 5 weeks before their mate’s parturition with those of virgin males pair-housed with another male, as well as males housed with a nonbreeding (tubally ligated) female. Both experienced and new breeding males weighed significantly less than virgins. Body mass did not differ between males paired with another male and those housed with a nonbreeding female; however, mass was lower in males housed with a