[Population (age and sex) structure of foxes in rabies-free and invaded areas]

Post mortem analysis of 1259 foxes from all over France, between 1976 and 1980, allowed comparison of age-structure of fox populations from long-time invaded areas (enzootic situation) or rabies-free areas. Heads received for rabies diagnosis have been aged by the cementum annulation technique, the sex of 650 of these foxes was known or fixed by examination of cells of the brain tissue for sex chromatin (found only in females). Results led to the generalization that young foxes (5-13 months) contracted rabies less frequently than did other ones. Consequently in rabies enzootic areas the age-structure of the fox population was lowered. The effect of 'gazage des terriers' (i.e. shooting foxes bolted from their holes with tear gas), which killed four females for each male, probably reduced the proportion of vixen in the population. No other obvious differences existed between sex-ratios. Consequently rabies does not seem to exercise any influence on this second parameter. The consequence of these results on the fox-culling is discussed.