Sexual dimorphism and sex identification in the South American culpeo fox,Pseudalopex culpaeus (Carnivora : Canidae)

Sexual dimorphism is analysed in skulls of the culpeo fox, Pseudalopex culp aeus, through multivariate and univariate approaches. The species shows a m oderate level of sexual dimorphism with most cranial variables being, on av erage, 5% larger in males. Equations are obtained for inferring the sex of skulls of juvenile, subadult and adult culpeo foxes. The equations are base d on a reduced set of variables obtained from stepwise discriminant analyse s by age class on skull measurements. The discriminant power of all functio ns is estimated on the basis of a jack-knife reclassification procedure. Co rrect classification is higher than 85% for both sexes, and is similar to, or higher than, the values reported for other foxes. The use of the discrim inant function pooling subadult and adult skulls is recommended because it shows a high percentage of correct classification without the necessity of ascribing a collected skull to the subadult or adult age class before sex e stimation. The equations provide an easy method to estimate the sex ratio o f wild populations of this furbearer species using the abundant carcasses d iscarded throughout northwestern Patagonia as a result of the intense hunti ng of the species. The information on sex ratios will help in the study of population dynamics and when monitoring the harvest of culpeo foxes.