The Trivers and Willard model (TWM) predicts that for sexually dimorphic polygynous mammals, mothers able to provide a high level of care should bias offspring sex ratio in favor of sons. Contradictory results of empirical studies, however, suggest that selective pressures for adaptive offspring...

Multiple mating by females is common in many mammalian species, often resulting in mixed paternity litters. In such mating systems, mating order, male age, and male body mass frequently play an important role in determining male reproductive success. We tested for these effects on male...