Bats in Finland

Little is known about Finland's bats. The ways of these mysterious flying mammals have eluded bat specialists to this day. Where do bats spend their winters? How common -or how rare- are the nine species commonly seen in Finland? Identification of bats in flight is difficult without special equipment. The most commonly used instrument is the bat-radar, an ultrasonic detector, with the help of which sounds emitted by the bats can be heard. There are about ten of these apparatus in Finland.

The most common bat in Finland is the northern bat (Etesicus nilssoni), with a range from Hanko until Ruija, Norway. In the very north of Finland bats are quite scarce. The rarest species is the natterer's bat (Myotis nattereri), which is only encountered in a few places along the southern coast. As a general rule, most of the species are aggregated in southern Finland. Only a few of the thirty European bat species have been able to adjust to the bitter winter cold and the intense light in the summer. Some bats feel at home in man-made environments. This is of great help to researches, as bats living in attics are easier to find than those hiding in the hollows of trees. On the other hand, living alongside humans is also a risk. If the owners of the dwelling grow weary of the squeaking in their walls, the whole colony might have to go. Disturbances like these have disastrous consequences, as each female has only one young at a time so that populations increase very slowly. In some cases, hundreds of bats can live in one community. Especially females are known to form 'kindergarten colonies', where they live together with their offspring. When the mothers venture out at night to catch insects, the young shiver side by side and keep each other warm. A female returning to the roost picks out her own offspring out of dozens of others and suckles it the same way that other mammals feed their young.

Apparently, during the winter bats prefer damp, cool places such as caves and cellars, to attics. Individual bats have also been found in war time bunkers. However not all of Finland's species hibernate inside the country. Some fly south, and in the Baltic countries there have been instances of migrations from the coast of the Baltic Sea to the Alps. Also Finnish birding amateurs have captured bats along with birds when banding individuals out of the spring and fall migrations. Information locations where bats spend their winters is badly needed, as there are very few clues of wintering bats. Bat specialists and amateurs have expressly searched for locations of bat hibernation, but so far the bats have stayed hidden. From the conservation point of view it is important that the most used overwintering places are discovered so that tranquil conditions could be guaranteed. Since so little is known about the way of life of bats, it has been difficult to identify factors that could be of threat to the species. The populations of many bat species have declined in central Europe. This is blamed partly on changes in waterways and destruction of habitat. Also, poisonous chemicals used in preventing decay have caused problems in some cases.

Bats have also suffered because of old superstitions. Fortunately, public awareness has had a positive effect on this issue. Far from being the devil's henchmen, bats are fascinating flying mammals, and on top of everything a single bat can eat tens of thousands of insects during a single summer season.