Regresión reciente y general del desmán ibérico en su límite noreste de distribución

Abstract

The update of the data about distribution and frequency of the desman (Galemys pyrenaicus) in Catalonia and Andorra –on its northeastern distribution limit- shows a recent and very important regression of this species. This information has been obtained with the monitoring of the desman in 420 river sections in the periods 2000-2003 and 2013-2107. The regression is mainly reflected in the relative frequency of the species and affects all the river basins, with a decrease in the positive points percentages of 43% in Catalonia and 70% in Andorra. An apparent local extinction is also observed in several river courses, in most of which the desman had an important presence in 2000-2003. The causes of this general regression are unknown, although it is assumed that there is no single cause and that it has been the result of the addition of several local factors. The factors that may have affected are the historical fragmentation of the populations, changes in the management of hydroelectric power plants, the increase in water demand in the Pyrenean valleys, public works in the rivers and some episodes of catastrophic floods. A factor that may have also contributed to the regression is the recent recolonization of the otter (Lutra lutra) in rivers with desmans, which could have generated a dangerous depredation over small and fragile populations. On the contrary, climate change does not seem to have influenced, since the desman does not show a negative trend in rivers of the southern limit with less suitable climatic conditions. As a consequence of this recent regression, applying the criteria of the IUCN, the desman must be considered a threatened species in the study area, with the categories EN-Endangered in Catalonia and CR-Critically Endangered in Andorra.