Evidencias de una ocupación temporal por parte del desmán ibérico (Galemys pyrenaicus) de cursos fluviales, con una marcada estacionalidad, en el norte de Portugal

Abstract

The population of Iberian desman of Tâmega river basin (Northern Portugal) was monitored between 2010 and 2012. The methodology was based on collecting potential desman faeces in river sections, previously selected by presenting favorable conditions, and subsequent confirmation of the specific identity by molecular techniques and by analysis of typical hairs found in them. Each river section was surveyed in two different seasonal periods: April - May, when flow level is high, and August - September, under maximum drought conditions. More than 130 river sections were surveyed, corresponding to 55 rivers and streams of different characteristics. The presence of Iberian desman was confirmed in 26 rivers, representing about 27% of the monitored river sections. Significant changes were found between the end of rainy season and the maximum of the dry season, concerning the presence of Iberian desman in certain river sections. In these cases, a dramatic decrease in the occupation was observed when comparing spring results with those of the dry season. The results suggest that in rivers with highly variable seasonal flow levels, desmans perform seasonal movements between main rivers and small tributaries, searching for adequate living conditions, movements which sometimes drive to the absence of water in river sections up to 6 km long. Even assuming that desmans living in environments subjected to marked seasonality are able to carry out large dispersive movements, the risk of extinction of small subpopulations due to severe and persistent drought is very high.