Mistério das fêmeas com chifres resolvido

quarta-feira, setembro 23, 2009

Evolution of weaponry in female bovids

Theodore Stankowich 1,* and Tim Caro 2

+ Author Affiliations

1Organismic and Evolutionary Biology, Department of Biology, University of Massachusetts, Amherst, MA 01003, USA

2Department of Wildlife, Fish and Conservation Biology and Center for Population Biology, University of California, Davis, CA 95616, USA

*Author for correspondence (teds@bio.umass.edu).


Weaponry is ubiquitous in male ungulates and is driven by intrasexual selection, but the mystery surrounding its sporadic presence in females remains unsolved. Female horns are often smaller and shaped differently to male horns, suggesting a different function; indeed, hypotheses explaining the presence of female horns include competition for food, male mollification and defence against predators. Here we use comparative phylogenetic analyses to show that females are significantly more likely to bear horns in bovids that are conspicuous due to large body size and living in open habitats than inconspicuous species living in closed habitats or that are small. An inability to rely on crypsis or take refuge in deep vegetation has apparently driven the evolution of horns for defence against predators in female bovids, a finding supported by many field observations. Typically, exceptions are small species where females are territorial (e.g. duikers) and use horns in intrasexual contests. Furthermore, we suggest that conspicuousness and territoriality hypotheses may explain other instances of female cranial weaponry (i.e. antlers and ossicones) in other horned ruminants. Our phylogenetic reconstruction indicates that the primary function of horns in females is linked to antipredator defence in most clades, but occasionally to intrasexual competition in others.

horns bovidae antlers weaponry territoriality antipredator