Els micromamífers semiaquàtics d'Andorra: distribució i estat de conservació

(ENG) The characteristic habitat for the desman in Andorra is the rivers and streams situated at low-medium altitudes (up to around 1900m) with a fairly pronounced slope (between 2 and 10%), a width of between 2 and 5 m, a maximum depth of between 0.5 and 1m, a rocky bed with good hiding places (cavities under rocks or tree roots), dense riverbanks vegetation (tall grasses, thickets or woods), with very little or no contamination and without the flow being artificially regulated by hydroelectric works. There are, in fact, no great differences between the habitat of the species in Andorra and the rest of the Pyrenees, although in some areas (particularly those with Atlantic influence) they can be found in more diverse waterways. The factors which condition its presence are all linked to the availability of food or areas in which to hide. The slope, width, depth and rocky bed are related to feeding: the desman feeds exclusively on invertebrates which live in the rocky beds of rivers with oxygenated water and needs these rivers to have a considerable flow year-round, as otherwise the number of invertebrates living in the river would be insufficient. In other areas this species also live in larger rivers, but in Andorra these are too polluted or regulated. The contamination and artificial regulation of the flow cause a fairly significant drop in the population of aquatic insects which the desman feeds off. The desman can tolerate slight organic contamination or flow regulation, but disappears as soon as these human disturbances intensify. Apart from the availability of food, the existence of refuges in which to hide is crucial for the desman. These include holes in the riverbanks to sleep in and cavities between the rocks in the river in which to hide when hunting. The desman can therefore be found in river courses which have a significant amount of holes in the riverbank and bed as well as dense vegetation.