Data from: Paternal reproductive success drives sex allocation in a wild mammal

Parents should bias sex allocation toward offspring of the sex most likely
to provide higher fitness returns. Trivers and Willard proposed that for
polygynous mammals, females should adjust sex-ratio at conception or bias
allocation of resources toward the most profitable sex, according to their
own body condition. However, the possibility that mammalian fathers may
influence sex allocation has seldom been considered. Here, we show that
the probability of having a son increased from 0.31 to 0.60 with sire
reproductive success in wild bighorn sheep (Ovis canadensis). Furthermore,
our results suggest that females fertilized by relatively unsuccessful
sires allocated more energy during lactation to daughters than to sons,
while the opposite occurred for females fertilized by successful sires.
The pattern of sex-biased offspring production appears adaptive because
paternal reproductive success reduced the fitness of daughters and
increased the average annual weaning success of sons, independently of
maternal allocation to the offspring. Our results illustrate that sex
allocation can be driven by paternal phenotype, with profound influences
on the strength of sexual selection and on conflicts of interest between
parents.