Bats in the Voorberg and the Jezuïetenberg

Abstract: The numbers of hibernating bats in the Voorberg-Jezuïetenberg marl quarry complex, southwest of Maastricht, were monitored between 1987 and 2020 by means of annual counts at the turn of the year. The numbers counted in that period grew from 30 to 99, mainly as the result of an increase in the number of Geoffroy’s bats. In the 2008-2009 season, it was investigated whether bats are home-steady during the hibernation season. It turns out that all species regularly woke up and moved around. The three-weekly counts in 2008-2009 also showed that most species gradually move towards the exit during the hibernation period, with only the Geoffroy’s bats remaining in the rear part of the complex. Most species leave the quarry around the end of March, with the exception of Geoffroy’s bats, which stay until mid-May.