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

Abstract

Studies of biparental mammals demonstrate that males may undergo systematic changes in body mass as a consequence of changes in reproductive status; however, these studies typically have not teased apart effects of specific social and reproductive factors, such as cohabitation with a female per se, cohabitation with a breeding female specifically, and engagement in paternal care. We aimed to determine whether California mouse (Peromyscus californicus) fathers undergo systematic changes in body mass and if so, which specific social/reproductive factor(s) might contribute to these changes. We compared mean weekly body masses over a 5-week period in 1) males housed with another male vs. males housed with a non-reproductive (tubally ligated) female; 2) males housed with a tubally ligated female vs. males housed with a female that was undergoing her first pregnancy; and 3) experienced fathers housed with vs. without pups during their mate’s subsequent pregnancy. Body mass did not differ between males housed with another male and those housed with a non-reproductive female; however, males housed with a non-reproductive female were significantly heavier than those housed with a primiparous female. Among experienced fathers, those housed with pups from their previous litter underwent significant increases in body mass across their mates’ pregnancy, whereas fathers housed without pups did not. These results suggest that male body mass is reduced by cohabitation with a breeding (pregnant) female, but not by cohabitation with a non-reproductive female, and that increases in body mass across the mate’s pregnancy are associated with concurrent care of offspring rather than cohabitation with a pregnant female. Additional work is needed to determine the mechanisms and functional significance, if any, of these changes in male body mass with reproductive condition.

Consequences of Fatherhood in the Biparental California Mouse (Peromyscus californicus): Locomotor Performance, Metabolic Rate, and Organ Masses

“…First, unlike the previous study (Saltzman et al 2015), we did not find differences among groups in body mass. Second, given how often males were tested (Table 1), it is possible that stress or some sort of carryover effects overshadowed any effect fatherhood may have had on speed, endurance or $\dot{V}{O}_2$ max.…”

“…Second, previous studies have shown breeding male California mice to have reduced circulating androgen levels (Trainor et al 2003), which could adversely affect muscle performance. Third, a previous study found reduced body mass in males housed with breeding (primigravid) females as compared with non-breeding males (Saltzman et al 2015), suggesting that reproductive status affects body condition in male California mice. Our predictions were not upheld by results of the present study, as we found no statistically significant differences in performance among males maintained in the three reproductive conditions (Table 2).…”

“…In several biparental species, fatherhood can affect body mass and body composition (Ziegler et al 2006; Campbell et al 2009). For example, in California mice ( Peromyscus californicus ), males housed with primigravid females did not gain mass over the course of their mates’ pregnancy, whereas age-matched males housed with a nonbreeding (tubally ligated) female showed significant increases in mass (Saltzman et al 2015). Moreover, relative masses of several organs (adrenal gland, thymus, spleen) differed between California mouse fathers and non-fathers (de Jong et al 2013; see also Harris et al 2013).…”

“…If fathers lose a significant portion of their body mass post-partum, then locomotor performance could be affected as well. It is not known if decreases in body mass in fathers of biparental mammals are completely accounted for by changes in body fat or if visceral organs and/or skeletal muscle are also altered (Saltzman et al, 2015). Changes in heart, skeletal muscle or lung mass and associated changes in cardiovascular or respiratory function might alter locomotor performance or maximal aerobic metabolic rate ( $\dot{V}{O}_2$ max).…”

Challenges to the Pair Bond: Neural and Hormonal Effects of Separation and Reunion in a Monogamous Primate

“…For instance, male prairie voles lose significant amounts of weight when caring for their first litter, demonstrated by drops in fat depots and circulating leptin (Campbell et al, 2009), as well as plasma insulin (Conley, 2012). In socially monogamous California mice, male body mass decreased when paired with a breeding female, and increased during their pair mate’s pregnancies (Saltzman et al, 2015). Male tamarins and marmosets gain weight during their mates’ pregnancies (Ziegler et al, 2006; Sánchez et al, 2008) and lose weight during periods of infant care (Sánchez et al, 1999).…”