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

摘要

Although effects of motherhood on mothers have been well documented in mammals, the effects of fatherhood on fathers are not well known. We evaluated effects of being a father on key metabolic and performance measures in the California mouse, Peromyscus californicus. California mice are genetically monogamous in the wild, and fathers show similar parental behavior to mothers, with the exception of lactation. To investigate the impact of fatherhood on fathers, focal males were paired with an intact female (breeding males), a tubally ligated female (non-breeding males) or another male (virgins). Starting 3–5 days after the birth of each breeding pair’s first litter, males were tested for locomotor performance (maximum sprint speed, treadmill endurance), basal metabolic rate (BMR), and maximum oxygen consumption (VO2max). At the end of the 11-day test period, mice were euthanized, hematocrit determined, and organs weighed. Speed, endurance, and V˙O2 max were significantly repeatable between two replicate measurement days but did not differ among groups, nor did BMR. Breeding males had larger significantly hindlimb muscles than did non-breeding males, whereas virgin males had heavier subcutaneous fat pads than non-breeding and breeding males. Several correlations were observed at the level of individual variation (residuals from ANCOVA models), including positive correlations for endurance with V˙O2 max, V˙O2 max with testes mass, and some of the digestion-related organs with each other. These results indicate that fatherhood may not have pronounced performance, metabolic or morphological effects on fathers, at least under standard laboratory conditions and across a single breeding cycle.