Premating and gestational effects of maternal nutrition on secondary sex ratio in house mice.

Pregnant female house mice maintained on a consistent low-food diet give birth to a lower proportion of males than do control females fed ad libitum. Because house mice may experience daily fluctuations in food availability, we tested whether intermittent feeding during gestation influences the sex ratio of the offspring. In addition, we tested whether intermittent feeding has asymmetrical effects on the masses of adult male and female offspring. Females deprived of food every other day one week before mating and those deprived every third day during gestation produced a lower proportion of males than did control (fed ad libitum) females. Males born to females that were deprived of food during gestation had the same body mass at birth as males born to control females, but as adults their mass was lower than that of control males. There were no differences in the birth or adult body masses of female offspring. Because males of low body mass may have relatively low lifetime reproduction, our results support the Trivers-Willard model of sex ratio variation.