Why are group-living badgers (Meles meles) sexually dimorphic?

One of the hypotheses proposed to account for why badgers Meles meles are h ighly social in the U.K., the resource dispersion hypothesis, is that patch y resources are unpredictably dispersed in the environment and therefore mu st be shared, but that these patches are rich enough, when available, to su pport several badgers at any one time. Previous empiricists in our study si te at Wytham Woods calculated that single patches could be rich enough to s upport 30 badgers in a night. The sustained increase in population density in Wytham Woods suggests that food was riot limiting and territories were b elow capacity, and therefore that feeding competition was relatively low. L ow feeding competition would predict an absence of dimorphism in trophic ap paratus between the sexes. Contrary to this, significant sexual dimorphism was found, after removing effects resulting from body size allometry, in ca nine cross-section length, width (both P < 0.0001) and skull breadth (P < 0 .001). The differences in canine dimensions were still significant when all ometry of both body length and skull breadth are accounted for statisticall y (P < 0.0001). It is therefore suggested that feeding competition may not necessarily be low, which would have implications for understanding the cos ts of social behaviour. Alternative explanations involving sexual selection and phylogenetic inertia are discussed.