Horn asymmetry and fitness in gemsbok, Oryx g. gazella

The relationship between fluctuating asymmetry in horns of gemsbok (Oryx g. gazella) and a number of fitness components was determined in a field study in Etosha National Park, Namibia. The length and width of horns and skull length demonstrated fluctuating asymmetry. Both males and females with asymmetric horns were in poorer condition than symmetric individuals. Individuals of both sexes with symmetric horns more often won aggressive interactions at water holes. Although symmetric individuals spent more time in dense vegetation, their vigilance rate was not higher than that of asymmetric individuals. Territorial, single males had more symmetric horns than males in herds, suggesting that mating success was inversely related to horn asymmetry. Females with symmetric horns more often had calves than asymmetric females. Horn asymmetry thus appears to reliably reveal phenotypic quality as demonstrated by a suite of fitness components.