Sunday 19 May
Serotine bat (Eptesicus serotinus)
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Serotine bat fact file
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Serotine bat description
One of the largest bats in Britain (5), the serotine bat (Eptesicus serotinus) has long fur, the back is smoky-brown in colour, while the belly is a paler yellowish-brown, the nose and triangular shaped ears are black, and the wing membranes are dark black or brown (2). Juveniles are darker in colour than adults (2). This species is easy to identify in flight, as its broad wings and slow, highly manoeuvrable flapping flight interspersed with brief glides is characteristic (5).
- Grande Sérotine, Sérotine Commune.
- MURCIÉLAGO HORTELANO.
- Tail length: 46 - 54 mm (2)
- Forearm length: 48 - 57 mm (2)
- Head-body length: 62 - 82 mm (2)
- Ear: 14 - 22 mm (2)
- Wingspan: 315 - 380 mm (2)
- 14 - 33 g (2)
Serotine bat biology
Bats are the only true flying mammals. In Britain they are insectivorous (eat insects), and contrary to popular misconception they are not blind; many can actually see very well (6). All British bats use 'echolocation' to orient themselves at night. Bats emit bursts of sound that are of such high frequencies they are beyond the human range of hearing, and are therefore called 'ultrasound' (7). They then listen to and interpret the echoes bounced back from objects, including prey, around them, allowing them to build up a 'sound-picture' of their surroundings (7). The serotine bat emits echolocation calls in the range of 15 to 65 kHz, but most calls are at 25 to 30 kHz (5). It emerges at early dusk (2), often when it still fairly light (5), and hunts mainly for beetles such as chafers and dung beetles as well as flies and moths (5).
The mating season starts in August, but its duration is unknown (2); very little is known of the mating behaviour of the serotine bat (5). Fertilisation is delayed; the females store sperm internally throughout the winter hibernation until spring (6). Maternity colonies, usually consisting of 10 to 50 females (6) begin to form in May (5). A single young is produced, usually in early July, and if the colony is disturbed during its first few days of life, the mother may carry it to a new site (5). By the third week of life the young bat is able to fly, and at around five weeks it is able to forage independently (2). During the summer, males are solitary or occur in small groups (5), but they occur with females in spring and autumn (6). This species hibernates between October and late March or April (2). Serotine bats can live up to 19 years of age (2).Top
Serotine bat range
Occurs throughout much of continental Europe, extending as far north as southern Sweden, southern England and Denmark, and south to the Mediterranean and Balkans (2). In Great Britain the serotine bat occurs roughly to the south of a line drawn between south Wales and The Wash (5); it is abundant in Sussex and Dorset, but very rare in Wales, and it is not known if the population is declining or stable (6).Top
Serotine bat habitat
Occurs mainly in lowland areas, where there are human settlements. The serotine bat has become very well adapted to man-made roosting sites, so much so that it is now only rarely found in natural sites (7). In summer they roost in buildings that have high gables and cavity walls, they are thought to typically remain in the same building to hibernate during winter. Some hibernating serotine bats have been found in caves, but this is rare (5).Top
Serotine bat status
The serotine bat is classified as Least Concern (LC) on the IUCN Red List (1). In Britain all bats are fully protected under Schedule 5 of the Wildlife and Countryside Act (1981) as amended, and by the Conservation (Natural habitats etc) Regulations (1994) (3). An agreement on the Conservation of European Bats in Europe (EUROBATS) under the auspices of the Bonn Convention, also known as the Convention on Migratory Species (CMS) is in force, and all European bats are listed under Appendix II of the CMS (4).Top
Serotine bat threats
The serotine bat has declined in many areas throughout Europe. Loss of feeding habitat is thought to have played a part in the decline. Furthermore, as this bat roosts in buildings, it is vulnerable to disturbance from building work and toxic timber treatments (5).Top
Serotine bat conservation
In Britain, bats benefit from a very comprehensive level of legal protection (4). Under the Wildlife and Countryside Act it is illegal to intentionally kill, injure, take or sell a bat, posses a live bat or part of a bat, to intentionally (or in England and Wales, recklessly) damage, obstruct or destroy access to bat roosts. Under the Conservation Regulations it is an offence to damage or destroy breeding sites or resting places. Fines of up to £5,000 per bat affected and six months imprisonment are in place for these offences (3).Top
Find out more
Find out more about the conservation of the serotine bat and other British bats:
The Bat Conservation Trust: Species Information Sheet - Serotine Bat:
The Bat Conservation Trust:
The Vincent Wildlife Trust:
Amy Dunkley, The Bat Conservation Trust, London.
- A group of organisms living together, individuals in the group are not physiologically connected and may not be related, such as a colony of birds. Another meaning refers to organisms, such as bryozoans, which are composed of numerous genetically identical modules (also referred to as zooids or 'individuals'), which are produced by budding and remain physiologically connected.
- A winter survival strategy characteristic of some mammals in which an animal's metabolic rate slows down and a state of deep sleep is attained. Whilst hibernating, animals survive on stored reserves of fat that they have accumulated in summer. In insects, the correct term for hibernation is 'diapause', a temporary pause in development and growth. Any stage of the lifecycle (eggs, larvae, pupae or adults) may enter diapause, which is typically associated with winter.
IUCN Red List (April, 2011)
- Schober, W. and Grimmberger, E. (1987) A Guide to Bats of Britain and Europe. Hamlyn Publishing Group Limited, London.
Bats and the Law - a quick guide. Bat Conservation Trust (August, 2002)
- Morris, P. (1993) A Red Data Book for British Mammals. Mammal Society, Bristol.
The Bat Conservation Trust: Species Information Sheet - Serotine Bat (August, 2002)
Macdonald, D.W. and Tattersall, F.T. (2001) Britain's Mammals - The Challenge for Conservation. The Wildlife Conservation Research Unit, Oxford University. Available at:
- Altringham, J.D. (1996) Bats: Biology and Behaviour. Oxford University Press, Oxford.
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