Sex-specific offspring growth according to maternal testosterone, corticosterone, and glucose levels

Sex allocation theory in vertebrates has greatly benefited from the recent advances in studies on the physiological mechanisms of birth sex ratio variation (e.g., maternal glucose, stress, and testosterone levels). The same physiological mechanisms may, however, also mediate permanent sex-specific effects on individuals after birth. Together with biased maternal postpartum investment on sex allocation, they can have long-term fitness consequences for the offspring. We studied whether maternal preconception levels of serum glucose and testosterone, and fecal corticosterone metabolites differently influenced male and female pup weight until weaning in field voles (Microtus agrestis). In this species, high maternal preconception serum glucose and testosterone levels have previously been associated with the excess of male pups at birth. Our results suggest that male, but not female, pup weight increases with higher maternal preconception testosterone level whereas high maternal serum glucose level promoted female pup weight only. The level of maternal fecal corticosterone metabolites was not related to pup weight in either sex. These findings suggest that in field voles the same physiological mechanisms influencing sex ratio at birth may also influence offspring postnatal weight; however, such influences can act in conflict, as seen in the case of maternal glucose level.