First records of hibernating Leisler’s bats (Nyctalus leisleri) in Belgium and the Netherlands

Authors: René Janssen, Hans Vermeiren, Ruud Kaal & Daan Dekeukeleire

Leisler’s bat (Nyctalus leisleri) is a rare, but widespread species in Belgium and the Netherlands. The species typically roosts year-round in tree cavities, although bat boxes are also sometimes used (Boston et al. 2020). While Leisler’s bat is recorded across the region, known maternity roosts are limited to larger, ancient forest fragments in the south of Flanders and the eastern part of the Netherlands. Leisler’s bat is recorded from April to October (waarnemingen.be and waarneming.nl), but virtually nothing is known about hibernation of the species in Belgium and the Netherlands. In Europe the species is often considered migratory (Boston et al. 2020). Recoveries of ringed individuals (mainly in Germany and Spain) revealed that individuals from northwestern Europe migrate in a southwesterly direction, with several recoveries over more than 1500 km in the Iberian peninsula (Hutterer et al. 2005, Steffen et al. 2007). Ohlendorf et al. (2001) describe a case of......