EDP Foz-Tua: Cabrera vole (Microtus cabrerae) & Small Mammals - Baseline Studies [2008]

Study Extent

The data were collected within a 5-km buffer around the Tua lower valley (Northeast Portugal), up to 45 km from the mouth, and in Ferradosa stream (Douro sub-basin), in the municipalities of Carrazeda de Ansiães, Vila Flor, Murça and Mirandela.

Sampling

Sampling was designed to cover all the potential habitats of the Cabrera vole (fallows, bushes, riverine habitats with low vegetation) in and around the lower Tua valley affected by the Foz Tua dam. A preliminary selection of suitable places was made using aerial photos and other cartographic means, followed by a visit to the area. A total of 24 areas were initially selected based on the habitat characteristics, but only 20 were actually used for sampling. A total of 25 sampling plots located in 20 of the 24 areas with suitable habitat was surveyed for signs of the presence of microtidae (tracks, faeces, latrines) in November-December 2008. When this inspection was positive, the plot was earmarked for a trapping session, to confirm the presence of Cabrera vole. As a result of this survey, 22 sampling plots were selected for trapping. Each trapping session consisted in the installation of lines of “Sherman” traps distributed every 2 m in all suitable habitats of the sampling plot. The number of traps set at each point depended mainly on its area and the amount of presence signs detected. Traps were baited with apple, carrot and commercial cat food (for Soricidae) and were covered with vegetation carded cotton, to provide food and thermal comfort for captured individuals, respectively. Each trap was controlled at least twice a day (one in the morning and another in the late afternoon). Traps were baited in one day and remained set for more three consecutive days and nigths. All the captured specimens were administered with a light volatile ethyl ether anesthesia, to ensure a correct and safe manipulation procedure. Each specimen was individually assigned a temporary marking (haircut), aiming to recognize the animal in the event of a recapture situation, aged and sexed (with the exception of shrews when non-lactating), measured and subsequently released. The following biometric parameters were taken: body length (mm), tail length (mm), hind leg length (mm), ear length (mm) and weight (grams). All identifications were made with appropriate field guides (Mathias et al., 1998; Palomo and Gisbert, 2002). The dichotomous key of Castells and Mayo (1993) was used to separate the Cabrera vole from other species of microtidae. Whenever possible, a tissue sample (a small portion of the ear) was taken from all captured microtidae to confirm the species identification. This was performed through the amplification and sequencing of a mitochondrial gene, cytochrome b, which has 1140 base pairs (base pairs, bp) and is widely studied in the European populations of Microtus. The DNA of all collected Microtus samples was extracted using a Extraction kit ("Qiagen Dneasy Tissue Kit"). The sequences obtained were then compared with the sequences available on GenBank. The captures were carried out under the License No 176/2008/CAPT, issued on October 2008, by the Institute of Nature and Forests Conservation (ICNF) to the senior field technician.

Quality Control

All identifications were performed by qualified technicians

Method steps

1. To be completed

The taxonomic coverage of this dataset spans 1 phylum, 1 class, 2 orders, 3 families, 4 genera and 5 species.

1. Chordata
   rank: phylum
2. Mammalia
   rank: class
3. Rodentia
   rank: order
4. Eulipotyphla
   rank: order
5. Soricidae
   rank: family
6. Sciuridae
   rank: family
7. Muridae
   rank: family

The data were collected within a 5-km buffer around the valley of the River Tua (Northeast Portugal), up to 45 km from the mouth, in the municipalities of Carrazeda de Ansiães, Alijó, Murça, Vila Flor and Mirandela.