Evolution of increased competitiveness in cows trades offs with reduced milk yield, fertility and more masculine morphology

In some species females compete for food, foraging territories, mating, and nesting sites. Competing females can exhibit morphological, physiological and behavioral adaptations typical of males, which are commonly considered as secondary sexual traits. Competition and the development of traits increasing competitiveness require much energy and may exert adverse effects on fecundity and survival. From an evolutionary perspective, positive selection for increased competitiveness would then result in evolution of reduced values for traits related to fitness such as fecundity and survival. There is recent evidence for such evolutionary trade-offs involving male competition, but no study has considered competing females so far. Using data from competitions for dominance in cows (Bos taurus), we found negative genetic correlations between traits providing success in competition, i.e., fighting ability, and fitness traits related to milk production and with fertility (the inverse of parity-con...