Le gîte du Castor du Rhône (Castor fiber). Description et comportement constructeur

Résumé En

The Eurasian Beaver (Castor fiber) has different types of shelter in France. The burrow generally comprises a short tunnel which rises from beneath the surface of the water, and leads to an hemispheric dwelling place which is situated a few centimetres underneath the level of the water. The burrow is devoid of all material, apart from a mattress of wood, shreaded by the Beavers. The roof is often pierced by an air hole for ventilation. The burrow may vary in relation to the texture of the bank, the variations of the water level, the time period during which the burrow is used, etc. Therefore one can envisage a several levelled dwelling and a burrow with long tunnels ; others are repaired by a visible mass of logs which gradually resemble the hut. The hut is not dug inside the bank but is built above the bank. Contrary to former opinion, in France the Beaver constructs huts closely resembling those of the Canadian species ; that is to say, a dome of wood and mud, the structure of which is subject to incessant change depending on the number of animals and outside conditions (i. e. mainly, variations of water level and weather) . The hut can attain great heights while at the same time concealing many independent dwellings. Its origin can possibly stem from a tunnel in the hank or from the bottom of the pond. The Winter Store. This consists of a pile of willow and poplar branches immersed in close proximity to each other, which are accessible to the Beavers even in times of frost. This supply of the bark of Salicaceae enables these rodents to survive cold periods. The Screen stretches from the hut towards the water and hides the to-and-fro movements of the dwellers. Beavers can adapt themselves to unusual conditions. Thus they can construct huts of reed like those of the muskrat : they can live in caves or in the flooded basements of mills ; or indeed in outside shelters for a part of the year. Building Behaviour. The neural structures of the Beaver do not differ from those of other Bodents apart from the thickness of its brain cortex. However its building behaviour is unique among mammals. It enables the animal to transform its environment to suit its needs. The paper describes the different stages of hut building, from tunnels dug in the bank or from the bottom of a pond.