Northern bat
Eptesicus nilssonii
Demid Alexandrovich · Zoologicheskaya Street
Key facts in one look
- Size
- 8–16 g, wingspan 24–28 cm
- Diet
- Insectivore, mainly small flies
- Status in Georgia
- Very rare, 4 records
- Habitat
- Forest edges, mountains, settlements
- Family
- Vespertilionidae
- Conservation
- NE / LC
The northern bat is the most northerly bat of all: it reaches beyond the Arctic Circle, up to 70° latitude, and breeds there too. In Georgia, though, it is very rare: it has just four records, from Tbilisi, Nunisi and near Moliti and Zvare. It is a medium-sized, dark bat with a golden sheen on its back. It looks very much like the larger serotine, so only a specialist can confirm the species. If a bat flies into your home, do not touch it with bare hands.
Identification
Northern bat: how to identify it
A medium-sized bat with long, soft, dark brown to blackish fur whose tips are golden yellow. This gives the back a golden sheen. The belly is pale brown to buff, while the face, ears and wing membranes are dark brown. It resembles the serotine and Savi's pipistrelle.
Head and body 54–68 mm, tail 35–50 mm, forearm 37–44 mm, weight 8–16 g depending on the season. The wings are broad and long, spanning 24–28 cm. The tip of the tail sticks out 4–5 mm beyond the membrane.
The ears are short, rounded and fleshy, with five transverse folds. The lobe inside the ear, the tragus, is short, rounded and curves inward. The ears, nose and wings are black or blackish brown.
The serotine is much larger: its forearm is 48–58 mm and it weighs 18–25 g. The search calls of the two species are very similar to each other and to those of noctules. So telling them apart by echolocation is hard too, and a specialist identifies the species by taking measurements.
Savi's pipistrelle is smaller, 5–9 g, and calls at a higher frequency, 30–35 kHz. The northern bat's call usually peaks at 26–32 kHz. Do not catch a bat yourself: measuring it is a job for a researcher.
Often confused with
The northern bat is a bat of northern forests and high mountains. It flies fast, so it needs open places to hunt: open woodland, forest edges, parks, gardens, lakes, wetlands and mountain meadows. It occurs from sea level up to about 2900 m. Summer colonies are mostly in buildings, in roofs and walls, and sometimes in hollow trees. In Georgia it has four records, at about 380–750 m above sea level. One is from Tbilisi, dating from 1889. The other three were made in 2006: in Tbilisi at Turtle Lake, at the Nunisi resort and near a bridge close to Moliti and Zvare. Its distribution and numbers in the country are practically unstudied.
The northern bat feeds mainly on small flies, gnat-like insects. It takes fewer beetles, moths and true bugs. It hunts in the air 2–20 m above the ground, along forest edges and hedgerows, and around street lamps in towns. It can hunt insects at temperatures just above freezing. Females pick a small hunting territory of about 100 m² and defend it from others, sometimes for several years.
The northern bat is most active twice a night: after sunset and around dawn. Hibernation lasts from November or December to March or April. It hibernates alone, in houses, cellars and sometimes caves and mines, at 0–2°C. It is mostly sedentary, although single animals move up to 450 km. Mating takes place in autumn; the female stores the male's sperm over winter and becomes pregnant in spring. Births fall between mid-June and the end of July, with one or two young. The young start flying at two to three weeks old. In summer, females gather in maternity colonies, while males live alone. In the wild it lives up to about 20 years.
In Georgia the northern bat was not evaluated in the 2021 national assessment (NE), and its population trend is unknown. Globally it is not threatened (LC, 2016): it is widespread and sometimes considered the most numerous bat in northern countries. In some countries it is still rare and locally threatened, for example in Germany. In Sweden its numbers fell sharply over 30 years. Climate change is seen as the main threat, because much of its range lies in the north, where warming is changing habitats strongly. The destruction and disturbance of day roosts and hibernation sites is a threat too.
Related guides
Continue with related pages
Yes, but it is very rare. It has only four records in the country: one from Tbilisi in 1889 and three from 2006. The latter come from Turtle Lake in Tbilisi, the Nunisi resort and the area of Moliti and Zvare. Its distribution in Georgia still needs study.
Mainly in size. The northern bat's forearm is 37–44 mm, the serotine's 48–58 mm. The northern bat's back fur is darker and has a golden sheen. Their calls are hard to tell apart, so a researcher identifies the species by measuring it.
Because it lives farther north than any other bat. It lives beyond the Arctic Circle, up to 70° latitude, and breeds there too. Because summer nights are short in the north, females there also fly by day. It hunts even at temperatures just above freezing.
Mainly small flies, gnat-like insects. Fewer beetles, moths and true bugs. It hunts in the air along forest edges and around street lamps, 2–20 m above the ground.
No, it is not venomous and does not attack you. But do not touch any bat with bare hands, because rabies cannot be ruled out by looks. If a bat bites or scratches you, wash the spot with soap and water for at least 15 minutes and see a doctor at once. In an emergency, call 112.
References
What this profile is based on
Species profiles are compiled from peer-reviewed literature and established biodiversity databases, and are reviewed as new taxonomic and conservation data become available.
Prepared by the Reptiles.ge editorial team from the sources listed here.
