První nálezy a fenologie netopýra Saviova (Hypsugo savii) na Děčínsku (Chiroptera: Vespertilionidae) [First findings and phenology of Hypsugo savii in the Děčín District, Czech Republic (Chiroptera: Vespertilionidae)]
Pavel Benda, Tomáš Bartonička, Jakub Juda
As a part of the bat research in the Děčín district (northern Bohemia, Czech Republic), two automatic detectors were installed at two locations, i.e. in the Labe (Elbe) river canyon near Hřensko and at the Pavlínka pond near Jetřichovice, for a period from April to September 2016. The acoustic recordings were further analysed using the semi-automatic software SonoChiro, which is capable of evaluating a large number of bat signals in a relatively short time. Altogether 942,000 echolocation signals and 18 bat species were determined. The highest values of the identification reliability index were found for the recordings of echolocation signals of the bat genera Pipistrellus, Nyctalus, and Vespertilio. Conversely, species of the genus Myotis, especially those with the peak frequencies above 35 kHz, were identified with a lesser accuracy. Hypsugo savii, a Mediterranean species that has been spreading over the past decade, was identified in both studied localities. This is the northernmost finding of the species in central Europe so far. Significantly higher flight activity of H. savii was detected in the Elbe canyon. The recordings were made in three periods: (1) from mid-April to late May, during the spring migrations, (2) in the second half of July, during the dispersion of individuals after the desintegration of the nursery colonies, and (3) from late August to early September, during the autumn migration, when the highest numbers of signals were detected. In the period of spring migration and summer dispersion, most of the signals come from the bats heading north, downstream the Elbe river. On the contrary, during the autumn migration, most of the signals were recorded from the bats heading south, upstream the river. The echolocation signals of H. savii can be easily identified and thus an acoustic approach in the study of migration phenology would be an appropriate and very effective method in this species.