While males fight, females choose: male phenotypic quality informs female mate choice in mammals

Theoretical support exists for an exaggerated male structure to serve as both a weapon for intrasexual competition and as an ornament to signal quality and promote female choice. However, there is little, if any, evidence to support this theory in male-male competition breeding systems. Using white-tailed deer, Odocoileus virginianus, as a model species, we manipulated antler size on males while controlling for body size and age and allowed 25 oestrous females the opportunity to choose between pairs of segregated males with either large or small antlers. By segregating males, we were able to remove any intrasexual male competition and isolate the effects of female choice. Using various behavioural indications of female choice, we demonstrate that females prefer males with large antlers to those with small antlers. Because antler size is heritable in deer, this female preference for larger antlers may be adaptive by increasing the reproductive success of her male offspring. Our unique antler manipulation study supports the armament-ornament model where male weapons can simultaneously serve as ornaments to females and weapons in male-male competition breeding systems.