Serotine
Eptesicus serotinus
eduardmarques · Girona
Key facts in one look
- Diet
- Insectivore, mainly large beetles
- Status in Georgia
- Widespread, 160 records
- Size
- 18–25 g, wingspan about 37 cm
- Habitat
- Settlements, forest edges, pastures
- Family
- Vespertilionidae
- Conservation
- LC / LC
The serotine is one of Georgia's most frequently recorded bats: it has 160 records, from Batumi and Colchis to Shiraki and Tusheti. It is a large bat of 18–25 g, with broad wings spanning up to 37 cm. It spends the day mostly in buildings, in cracks in walls and roofs. It comes out early in the evening and flies slowly and nimbly. In Europe a large share of bat rabies cases come from this species, so do not touch it with bare hands.
Identification
Serotine: how to identify it
A large, robust bat with broad wings and fairly large ears. The back is smoky brown with a yellowish tinge, the belly paler. The face, ears and wing membranes are dark brown to blackish. In flight it gives itself away with its broad wings and slow, agile flight with short glides.
Head and body 62–82 mm, tail 39–65 mm, forearm 48–58 mm, weight 18–25 g. The wingspan is about 37 cm. The tip of the tail sticks out 3–5 mm beyond the membrane.
The fur is long, dense and silky. The back is smoky brown, with dark hair bases and yellowish tips, and some animals have an almost reddish tinge. The belly ranges from grey to pale brownish. Young bats are darker than adults.
The northern bat is clearly smaller, with a forearm of 37–44 mm, and its back is darker with a golden sheen. The serotine's call resembles that of the similarly sized common noctule. It differs from noctules in the lobe inside the ear, the tragus: in the serotine it is thin and pointed, in noctules kidney-shaped.
Its echolocation call usually peaks at 23–44 kHz. It differs from similar bats by its irregular, unrhythmic pattern, though its frequencies overlap with many species. So a specialist confirms the exact species; do not catch the bat by hand.
The serotine has adapted to living alongside people: it often spends the day in buildings, in cracks in walls, under roofs and in attics. It also uses bridges, rock crevices and cave entrances. To hunt it chooses open places: forest edges, riverside woods, gardens, pastures, town parks and water bodies. It occurs from semi-desert and scrub up to high mountain pastures. In Georgia it is widespread, with 160 records since 1885. It has been found in Adjara, including the Batumi Botanical Garden, in Kolkheti National Park, Borjomi, Tbilisi, the Gardabani managed reserve, Shiraki and Lagodekhi. It ranges from sea level to Omalo in Tusheti and Didmaghali, up to about 2000 m. It has been found in caves too, but it is a crevice bat, and underground sites are not its usual roost.
The serotine hunts large insects, mainly beetles. Its prey measures 5–25 mm: dung beetles, cockchafers, moths, true bugs and flies. It catches insects in the air, but it will also pick them off leaves or the ground. It often hunts around street lamps, along forest edges and over pastures. It chews a large beetle in flight and drops the wing cases and legs. In one night it visits up to 10 hunting sites, usually 4–12 km from its roost. It changes its food with place and season, which makes it a flexible hunter.
The serotine is one of the first bats out in the evening, about 20 minutes after sunset. It flies slowly and nimbly, with short glides, sometimes as high as 30 m. It is mostly sedentary; the longest known movement is about 330 km. It spends the winter mostly in buildings, in cavity walls and disused chimneys, and rarely in the coldest part of a cave. Maternity colonies gather from May to August, usually with 10–60 females and sometimes up to 300. Mating takes place in autumn, and the female stores the sperm over winter. Pregnancy lasts about 52 days, and births fall in June and July. It usually has one young; twins are rare. The young starts flying at three weeks and hunts on its own at 5–6 weeks. The oldest known individual was 19.5 years old.
In Georgia the serotine is not threatened (LC, 2021 national assessment), and its numbers are stable. Globally it is Least Concern too (LC, 2020) and common across much of its range. In some countries it is still declining: in Britain, Austria and the Pannonian Basin. In Austria its numbers fell by 70%, and it vanished from the lowlands in the east of the country. The main threats are disturbance and destruction of colonies in buildings during renovation, toxic timber treatments and the loss of hunting grounds rich in large insects.
Related guides
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Almost all over the country. Records range from Adjara and Colchis to Borjomi, Tbilisi, Shiraki and Lagodekhi. It reaches from sea level up to about 2000 m, as far as Omalo in Tusheti. It often lives in villages and towns, in buildings.
Do not disturb them and do not touch them with bare hands. The serotine often sets up its colonies in buildings, especially from May to August, when females raise their young. Do not disturb the colony or seal the attic at that time: the young only start flying at three weeks old. If you plan repairs, put them off until autumn, when the colony breaks up.
It can. In Europe more than 90% of bat rabies cases come from this species; it is the main carrier of the EBLV-1 virus. Most bats are not sick, but you cannot tell by looking. So do not touch it with bare hands. If a bat bites or scratches you, wash the spot with soap and water for at least 15 minutes, see a doctor at once, and in an emergency call 112.
Large insects, mainly beetles: dung beetles and cockchafers. It also eats moths, true bugs and flies. It often hunts around street lamps and over pastures. It catches insects in the air and also takes them from the ground.
In size. The serotine's forearm is 48–58 mm, the northern bat's 37–44 mm. The northern bat has a darker back with a golden sheen. In Georgia the serotine is far more common: it has 160 records, the northern bat only four.
It is not threatened either in Georgia or globally (LC), and its numbers in Georgia are stable. In some European countries it is still declining, by 70% in Austria. The main threat is the destruction of colonies in buildings, so look after the bats living in your attic.
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.
