Seasonal activity patterns of bats along urban watercourses

Abstract

Different bat species adapt to urban environments with varying efficiency. Urban watercourses may promote bats’ presence in the city but also, because of improper management, may become an impassable barrier. This work evaluated the bats’ presence in different urban riverside environments during the vegetation season. Bats’ activity was recorded in Cracow on the main river Vistula and its tributary Rudawa. Our results showed that long-range echolocators were represented mainly by Nyctalus noctula. Their activity peak occurred in late summer in open habitats with high anthropopressure levels, and at least part of the population is present year-round in the city. Recently reported from Cracow: Hypsugo savii and Pipistrellus kuhlii were confirmed in the medium-range echolocators. The high occurrence of P. pygmeus with a relatively low P. pipistrellus was noteworthy and is probably a result of the low competitiveness of the latter in the presence of P. kuhlii. Two spring and late summer activity peaks on different rivers suggest different migration corridors to and from hibernacula. However, the autumn activity in the city centre may also indicate partial hibernation in the old town. The activity peak of short-range echolocators occurred in spring, as expected - mainly in a narrow riverbed and low anthropopressure environments. Although, ambiguous spring and late summer activity in the open with the highest anthropopressure environment may result from the rapidly progressing synurbization of M. daubentonii. Our results indicate the need to monitor the bat adaptation process to the cities in the context of dynamic climatic and environmental changes.