Abandoned tunnels as habitats for bats and measures to improve habitat quality

Scientific investigation of the use of abondened railway tunnels as a habitat for bats.

A total of twelve tunnels at the Tauernbahn railway line in Carinthia, Austria, were abandoned due to a relocation of the main tracks.

As part of the ÖBB initiative “Green Points”, a project was launched to investigate the role of the tunnels as habitat for bats. Furthermore, measures for improving their habitat quality for bats were planned and put into action.

To obtain information about temperature and humidity conditions, we placed data loggers in some of the tunnels. Different bat species have different temperature requirements for their hibernation, so detailed knowledge about temperature range and fluctuations is of great importance.

The present use of the tunnels by hibernating bats was checked visually during the winter months. We were, however, also interested to find out if bats use the tunnels during summer. Therefore, we used automated recording devices for the recording of bat calls as well as mist netting.

So far, six bat species were registered in the tunnels: Lesser horseshoe bat (Rhinolophus hipposideros), Natterers’ bat (Myotis nattereri), Mouse-eared bat (Myotis myotis), Common pipistrelle (Pipistrellus pipistrellus), Barbastelle (Barbastella barbastellus) and a species of the genus Plecotus.

Based on the first results, conservation measures were applied: We made sure, i) that the tunnel entrances allow bats access and support the microclimatic conditions aimed for in the different tunnels, ii) that human disturbances in the tunnels are minimized, and iii) that hollow concrete blocks were placed in the tunnels to increase the number of available crevices for bats.

The effectiveness of these measures and the population trend of the bats will be monitored in the oncoming years. Thus, the results will provide important guidelines for the improvement of abandoned tunnels as habitats for bats.

Abandoned tunnels, Hibernacula, Bats, Austria