Influence of hurricane Lothar on red and roe deer winter diets in the Northern Vosges, France
Résumé
Extreme climatic events, such as hurricanes, may profoundly affect herbivore population dynamics and habitat use by returning tracts of mature forest to early seral stages where food and cover resources rapidly develop. Modifications of habitat use by roe deer (Capreolus capreolus) following hurricane Lothar have been demonstrated in a French forest, and it has been suggested that the combination of a reduction in hunting due to hunters' inability to access the areas and an improvement in habitat characteristics in clearings resulted in Lothar having a positive effect on roe deer population dynamics. Here, we studied the winter diet of red deer (Cervus elaphus) and roe deer before and after hurricane Lothar in a heavily damaged forest, assuming that the hurricane, by creating numerous clearings in which food availability for herbivores increased rapidly, allowed deer to specialize on preferred plant species that benefited from habitat modifications, particularly bramble and grasses. According to their feeding types and ecology, we expected that the increase in the availability of grasses and bramble after the hurricane would result in an increase in the proportions of these plants in the diet of red deer and an increase in the proportion of bramble in the diet of roe deer. Analysis of stomach contents revealed that consumption of grasses by red deer almost doubled following the hurricane, but no effect on bramble consumption by either deer species could be detected. Our study also revealed a significant annual variation in bramble consumption, which suggests that its availability as a food resource for deer varies from year to year, and this may have masked the hurricane effect. We then discuss the role of disturbances in improving habitat for forest ungulates, and the role of key alternative food resource in helping forest managers to find solutions for mitigating ungulate impact on tree regeneration.