Lutra 46(2)_Fustec & Gormier_2003

The habitat potential of the downstream Loire River for European beavers (Castor fiber)

During the 19th century the European beaver (Castor fiber) disappeared from most parts of France, except for the Rhône Valley. In the 1970s, beavers caught from the river Rhône were released in the Loire River, near the city of Blois. While this reintroduction was successful and led to the progressive recolonisation of the Loire River and its tributaries, the density of beaver colonies has remained low. Furthermore, habitat quality has decreased in the downstream part of the Loire, and beavers might not find enough suitable sites to settle. This study was designed to estimate the number of suitable places for beaver settlement in a downstream segment of the Loire River, which is still uncolonised, but already explored by pioneer individuals. For this purpose, we searched for relationships between signs of beaver presence (lodges, cut trunks, and remains of browsed plants) and vegetation features, bank characteristics, and human disturbance in a presently colonised region of the Loire River. Beavers selected sites dominated by 10-15 m tall trees to build lodges, irrespective of the tree species. Sites with cut trees were dominated by Salicaceae. Beavers fed on Salicaceae and numerous herbs. Based on these findings, vegetation features in the uncolonised stretch of the river are expected to be favourable to beaver settlement and feeding. However, beavers will have to face river bank protections and more intense levels of human activity in most of the uncolonised area. These factors may dramatically limit the number of sites suitable for lodge building.