Bats of the outer archipelago

The importance of the outer archipelago and open sea areas for bats is almost unknown in Finland. The endangered little bat is clearly a migratory species, but there is no precise information on migration routes. For example, Hankoniemi is identified as a migratory route, but there is no more detailed information on directions and the importance of the wider archipelago. It is also not known to what extent our other more abundant bat species, such as the ground bat and winged bat, migrate, or whether any of them use the outer archipelago, for example for hibernation. A few other bat species (including the big bat and the bumblebee) are also regularly found in Finland, but in low numbers, and their distribution and conservation status is poorly known.

Passive acoustic monitoring is the main method used in the project. The project area is the Archipelago Sea and the Åland Islands, as well as the offshore areas south of them. Ultrasonic loggers recording the echolocation sounds of bats will be installed at sites in the outer archipelago of Uusimaa, Southwest Finland and Åland, which are potential migration routes and/or are expected to provide a more accurate picture of the migratory behaviour of bat species to the sea and their presence in the outer archipelago and the open sea.

The data collected will be used to refine information on migration routes, timing of migration and species composition. Equipment will be placed in potential wintering sites on the outer archipelago during the winter (including devil’s fields) to assess whether bat species use island areas for hibernation.

The implementation is closely linked to the LIFE IP BIODIVERSEA project and supports the achievement of its objectives.