The Trivers and Willard model (TWM) predicts that for polygynous ungulates, females of high phenotypic quality should produce more sons than daughters, whereas females of low phenotypic quality should produce more daughters. Kruuk et al. showed that in red deer the TWM only applied when the...

For dimorphic species in which the variance in reproductive success of males is more pronounced than that of females, theories of adaptive variation in sex ratio predict that mothers should invest more heavily in sons than in daughters. By using harvest data from a forest-dwelling red deer...