Major decline of bat abundance and diversity during the last 50 years in southern Belgium.

In order to identify long-term population trends in bats in southern Belgium, we compared results of winter bat banding between 1939 and 1952 to winter bat counts between 1995 and 2008 in 58 hibernacula. The results show a strong decrease in the populations of Rhinolophus ferrumequinum, R. hipposideros, Barbastella barbastellus, Myotis dasycneme and M. myotis. In contrast M. daubentoni and M. mystacinus/brandtii/alcathoe show a numeric increase between these time periods. The bat diversity within these hibernacula has decreased by half over the last fifty years.