Constant Sex Ratios of Progeny in Nutritionally Stressed Wild House Mice

Data for wild house mice (Mus musculus) were analyzed to test the Trivers-Willard hypothesis of facultative sex-ratio adjustment as an adaptive response to stress (Trivers and Willard, 1973). Females were nutritionally deprived during the nursing period. Litters were examined for changes in secondary sex ratios and weight of offspring. Although 40% litter reduction occurred in food-restricted groups, sex ratios among offspring did not change significantly. Males grew faster than females in the food-restricted group. The results do not conform to predictions of the Trivers-Willard hypothesis and are discussed in light of the biology of M. musculus and current theory on adaptive control of progeny sex ratios in vertebrates.