Eptesicus nilssonii

Northern bat
Northern bat
Northern bat

Central and Eastern Europe, they are the only reproducing bat species north of the Arctic Circle.1 In Bulgaria only one individual has been found in Rila mountain.

A medium-sized bat. The dorsal fur is long, dark brown or brown-black with gold-yellow tips. The ventral side is yellowish-brown to beige, sharply delineated from the dorsal side. The skin areas are dark brown or black. The tail tip is free and measures up to 4 mm.

Up to 20 ms long QCF calls with peak frequencies between 26 – 29 kHz. The orientation call is typical with a “galloping” call impression. Mating calls are 60 ms long and in lower, audible frequency range.

Mountain forest areas, mountain pastures, rocky and karst regions. Can also be found in human settlements.

Roosts are in tree holes, bat boxes, rock and building crevices. During the winter, Northern bats form small groups in mines, bunkers and caves. It is considered that this species is sedentary, but there have been recorded distances from 100 km to 450 km. The foraging areas can be very small (20 ha) or very big (66 km²).

The copulation ocrrurs in the late summer. Nursery colonies comprise of 20 – 50 individuals. One or two young are born in June or July. After three weeks they can fly and hunt independently. The juvenile females can give birth in their first year of life.

The flight is slow. They hunt over open areas, around tree crowns and street lamps. This species can hunt even when the air temperature is slightly above freezing point. Their diet consists of small Diptera, beetles, moths and other flying insects.

Building renovations and wind turbines. Habitat changes also affects this species.

Christian Dietz and Andreas Kiefer (2014), “Bats of Britain and Europe”;

Vasil Popov, Atila Sedefchev (2003), “Mammals in Bulgaria”;

Vasil Popov, Nikolay Spasov, Teodora Ivanova, Borqna Mihaylova and Kiril Georgiev (2007), “Mammals important for conservation in Bulgaria”.