During the warm summer months, small bats appear on the water surface of Myllylähde, breaking the calm water surface when they eat insects. The silent flyers are Daubenton’s bats and dozens will flash around the spring. They are the third most common bat in Finland, weighing only 5-14 grams and have a body length of 4-5 cm while the fur is brownish-grey on the back and silvery-grey underneath and the patagium is grayish brown and relatively wide and thin.
As its Finnish name (water wings) suggests, it favours being close to waterways. Daubenton’s colonies are generally located near shorelines, often in tree hollows, natural or made by birds, which are usually located two metres high. That allows their young to be seen basking in the sun outside during daybreak. Also, on cool autumn days, they can be seen on tree trunks taking the sun. The species flies quickly along the surface of water on the bright summer evenings and between trees and they seek their prey before twilight, particularly favouring water caddis flies, but butterflies, black flies, mosquitoes and flies are also a source of nutrition. Daubenton’s bats have good flying skills and can hover in the air for a few moments and they can also swim.
They mate in the late summer, but do not fertilise until spring. The mother always gives birth to a single bat in July. In winter they shelter in basements, rock cavities or caves. As with most other types of bat, little is known about their wintering.
Photo: Ari Karhilahti