For species in which reproductive success is more variable in one sex than the other, the Trivers and Willard model (TWM) predicts that females are able to adjust their offspring sex ratio. High-quality mothers should provide greater investment to one sex than the other. Previous tests of the...

A deterministic epidemic model describes the propagation of Puumala hantavirus within the bank vole population of Clethrionomys glareolus. The host population is split into juvenile and adult individuals. Demographic parameters are time periodic. A further spatial structure is considered using a...

The consequence of helping behavior on breeders fitness is still controversial. We used multivariate analyses to investigate for the effects of male and female subordinates on breeders' components of fitness in the Alpine marmot, Marmota marmota. We found that male and female subordinates,...

In cooperatively breeding vertebrate species, a clear theoretical prediction about the direction of sex ratio adjustment can be made: mothers should bias the sex ratio of their offspring towards the helping sex when helpers are absent. A consistent trend in the direction predicted by theory...

Three main hypotheses have been proposed to explain mate switching in monogamous species: the "better option" hypothesis, the incompatibility hypothesis, and the "forced divorce" hypothesis. We tested the predictions of these hypotheses for the first time in a monogamous mammal using long-term...

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...

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...