Tactics of maternal investment of northern grasshopper mice in response to postnatal restriction of food

Abstract

Various theories predict sex-biased maternal investment under specific environmental or maternal conditions. The Trivers-Willard hypothesis, for instance, predicts that in some polygynous species maternal investment should be biased toward daughters when the mother is in poor condition. Empirical data testing this hypothesis are equivocal. I compared patterns of maternal investment in lactating northern grasshopper mice (Onychomys leucogaster) allowed unrestricted access to food with those of mothers that received 80% of requirements for non-lactating mice. Nutritionally deprived mothers either attempted to rear their entire litter, or killed and consumed all young before maternal mass dropped below 75% of initial mass. Growth rates of young from experimental litters were lower than those from control litters, but there was no evidence of sex-biased maternal investment.