Baixo Sabor: Bat acoustic sampling - Compensatory Measures Program (MC1) [2013-2014]

Sampling was designed to cover the most relevant feeding habitats for Chiroptera along the 5km final stretch of the Vilariça stream. Two sampling points located at least 100 m apart were set in the area. Each point was visited at least once per season: spring (April-May), reproduction (July) and post-breeding (August-October). Sampling was carried out when there were favourable weather conditions, including temperature above 10ºC and absence of strong winds and rainfall. Acoustic sampling in each plot was initiated at sunset and had a fixed duration of 90 minutes.
The detection of the 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 peformed 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.