Effects of anthropegenetic pressure on space occupation by alpine marmots [Effets de la pression anthropique chez les marmottes alpines].

Résumé

In Alpine environments, marmots are an important cause of landscape animation and are very attractive for summer tourists. A study of different ecological factors such as altitude, sun exposure, slope, plant cover has been performed on three marmot populations in the Alps. The study allowed the description of the impact of marmots on landscape and showed a preference for particular kinds of mountain landscape. Impact on landscape : marmots mark the landscape in two main ways. The first impact is their action on plant association when foraging. Plant removal has an effect on the maintenance of the open Alpine meadows. The selective grazing activity of marmots can compensate the decrease of pasture use by sheep and cattle which is occurring now in most parts of European mountains and which will extend in the coming years. The second impact is ground directed and related to digging activities of marmots. Alpine marmots use to dig numerous burrows (up to 400 per ha) even if they use regularly only a main burrow system. Old installed marmots use the same main burrow system during many years leading to mounds of more than one meter high and two or three meters in diameter. Such building appears on aerial photographs. The long term use of a place is also indicated by the presence of paths, of scratched areas and in some places of latrines. In sensitive geological areas, marmots can have an important action as erosive agents. On steep slopes they can induce landslides. Burrows are long lasting indices of marmot presence in a landscape and they can be used to analyse areas occupied by these animals thirty or forty years before. Selection of settlement site : The analysis of 88 plots of a quarter of Ha each allowed to define a generalised linear model showing a non randomised selection of landscape type. Slopes are preferred to flat areas. Mixed vegetation and rock areas are preferred to only rock or only plant areas. Southern or Eastern exposure are preferred to Northern or Western exposures. The selection of site settlement by marmots has consequences to particularise the mountain landscape as these places will be more frequented by hikers during summer, inducing other erosive effects and damage to landscape and plant communities.