Structure des populations de renard roux, Vulpes vulpes, dans le sud de la Belgique en relation avec l'enzootie rabique et les campagnes de vaccination orale

From 1989 to 1991, 549 fox carcasses were examined in order to assess the impact of rabies control measures (oral vaccination with VVTGgRAB recombinant vaccinia-rabies virus). Their age was determined using a lower canine tooth. The distinction between young and adults was made on radiographs, measuring the relative importance or the pulp cavity. Adult animals were aged by counting the annual growth cementum layers in tooth sections. The sex-ratio is in favour of the males and the age-pyramid is a large-base flattened one, with more than 60 % of young (< 1 year) animals. Life expectancy at birth is 1.14 y. in the males and 1.23 y. in the females. The population turnover is quite high, the whole population being renewed in a 3-4 y. time interval. As far as the age structure is concerned, no difference has been found between males and females, rabid and sound animals, immunised or not. However, the spring vaccination campaign is much less efficient for the young foxes. These results suggest that rabies affects indistinctly all age classes of both sexes, just as it is the case with the autumn vaccination campaigns. Moreover, a comparison between the samples of two natural regions differing in their hunting system (big vs. small game) revealed no age structure difference suggesting that the high hunting pressure can explain better than rabies itself the very important juvenile proportion in the population. Nevertheless, some further research is needed to confirm that last point.