Micromammals

The micromammal species included in the monitoring program are the European snow vole (Chionomys nivalis), the south-western water vole (Arvicola sapidus) and the Spanish mole (Talpa occidentalis). The three species have very different ecological requirements and thus the data derived from their monitoring reveal evolutionary aspects of the three welldifferentiated types of ecological systems. Below, the three methodologies used are described:

European snow vole (Chionomys nivalis): between June and August, the intensive monitoring is made in seven colonies. These colonies are found at different elevations and orientations. The study is made by live trapping with 30 folding Sherman traps © (8 x 9 x 23 cm).

South-western water vole (Arvicola sapidus): half-hour sampling sessions were conducted in each location likely to harbour this species. If the sampling proves positive, it is concluded and the time until locating this first indication is noted.

Spanish mole (Talpa occidentalis): given that the abundance of mole hills can be considered as an index of activity of this species, both the distribution as well as the abundance are inferred from these indirect indices in the field. A total of 18 transects 7.5 km long have been laid out with a total of four sampling stations per transect, roughly 2.5 m apart. In all, there are 72 stations or plots.

The same methodology is implemented once per year in the case of the snow vole (since 2008) and is repeated every two years in the case of the south-western water vole (since 2011) and the Spanish mole (2008 and 2010).