Antlers on Female Caribou

Abstract: Functional explanations for horns and antlers on female ungulates are conflicting. The authors tested the hypothesis that such appendages serve in intraspecific competition for resources by analyzing the tendency for female caribou to carry antlers across a 1000 km wide gradient. The authors predicted that females in populations experiencing more intense or more protracted interference competition, reflected as greater depth and duration of snow cover, would exhibit greater propensity to bear antlers. Among 15 herds in Newfoundland and Labrador, Canada, the percentage of antlered females was correlated positively with average annual snowfall and mean snow depth at the end of March, and negatively with population density. The results support the hypothesis that antlers on females provide functional advantages in interference competition for winter food, but that antler possession may decline in instances of higher animal densities and diminished nutritional state.