EDP Baixo Sabor: Acoustic Bat Monitoring – Construction and Reservoir Filling Phases [2008-2014]

Study Extent

The study was carried out in the lower reaches of the Sabor River (Northeast Portugal). The data were collected at sampling sites located in several habitats, both in the area to be flooded by the reservoirs and within a 5-km buffer around the area flooded by the reservoirs at the full storage level of the Sabor dams, encompassing a length of river of 90 km upstream of the mouth. Sampling was carried out in the municipalities of Torre de Moncorvo, Alfândega da Fé, Mogadouro, Macedo de Cavaleiros, Vimioso and Bragança.

Sampling

Sampling was designed to cover the dominant habitats occurring in the study area and that are normally used by foraging bats. A total of 97 sampling points was surveyed, stratified by habitat, considering the main habitat types represented in the region. Of these, 50 sites were located within the area flooded by the reservoir, 26 in areas above or around it, but outside its range of influence (2-5 km), and 21close to extant and future weirs in the tributaries of the River Sabor (above the flooded area). Each sampling site was visited once or twice per season, considering three seasons: spring (April-May), reproduction (July-August) and post-breeding (September-October). Sampling was carried out when there were favourable weather conditions, including temperature above 10º and absence of strong winds and rainfall. Acoustic sampling started at sunset and ended 2-3 hours later. Each site was sampled for 10 minutes. The detection of specimens in flight was made with a bat detector (Pettersson Elektronik, D240X model), with a frequency range of 10-120 kHz. The detector was connected to an automatic digital recorder (model Sony ICD-PX312) which saved the recordings in a “Wave” format, at a frequency of 44 kHz and at an expanded mode of 10x, making them audible to the human ears while, at the same time, preserving the original acoustic characteristics. The analysis of the acoustic records were performed using the sound analysis program BatSound Pro (Pettersson Elektronik AB). This program generates graphs (oscillogram, sonogram and power spectra) using the various sound variables that allow the identification of species or complexes of species detected. The exact identification of the bat species by sound analysis is not always possible, due to problems in detectability and/or identifiability. In the context of this work, whenever it was not possible to perform the identification to the species level , the binomials, multinomials or genera to which the identification was possible were considered to be present. Thus, the presence of all species constituting these phonic groups (or “species complexes”) was considered possible.

Quality Control

All individual identifications were performed by qualified technicians

Method steps

1. To be completed

The taxonomic coverage of this dataset spans 1 class, 1 order, 4 families, 10 genera and 17 species positively identified.

1. Chordata
   rank: phylum
2. Mammalia
   rank: class
3. Chiroptera
   rank: order
4. Rhinolophidae
   rank: family
5. Vespertilionidae
   rank: family
6. Miniopteridae
   rank: family
7. Molossidae
   rank: family

Data were collected in an area of 62,500 ha corresponding to 25 5x5 km squares around the lower Sabor river affected by the Sabor Dams (impact area), and in an additional area of 30,000 ha not directly affected by the dams, encompassing a set of 12 5x5 km squares (control area).