Serotine bat (Eptesicus serotinus) is one of Britain’s largest bat species and usually one of the first to appear in the evening, often emerging in good light. It can be found in the south and parts of south Wales.
On a bat detector serotines calls sound like irregular hand-clapping. The echolocation calls range from 15 to 65kHz and peak at 25 to 30kHz.
Serotines roost mainly in older buildings and churches with high gables and cavity walls.. They are one of the most building-oriented species and is hardly ever found in trees. They roost hidden in crevices around chimneys, in cavity walls, between felt or boarding and tiles or slates, beneath floorboards and sometimes in the open roof space at the ridge ends or occasionally elsewhere along the ridge. Very few serotines are found in winter, but it is likely that most hibernate in buildings. It is possible that at least part of the summer colony may remain in the same building for some, if not all, of the winter period. Hibernating serotines have been found inside cavity walls and disused chimneys
The Serotine has broad wings and is characteristic for its leisurely flapping flight with occasional short glides or steep descents. It flies at about tree-top height (to about 10 m) often close to vegetation, and will sometimes flop, wings outstretched, on to the foliage to catch large insects. It will feed around street lamps and even catch prey from the ground. When it catches a large beetle, the serotine will fly around slowly, chewing its prey and dropping the wing cases and legs; sometimes it will take the prey to a feeding perch. In spring it mainly feeds on flies and moths and in summer, particularly chafers and dung beetles.
The Serotine has dark brown fur above and pale fur underneath. Its face and ears are black. The head and body length is 58mm – 80mm and the wingspan 320mm – 380mm. The serotine weighs 15g – 35g.
Maternity colonies consist almost exclusively of female bats and start to build up in May. A colony usually remains at a single roost site during the breeding season. Females normally give birth to a single young in early July. The baby is occasionally carried by its mother for the first few days. At 3 weeks the young are able to make their first flight and at 6 weeks they can forage for themselves. Mating normally takes place in the autumn, but almost nothing is known of the mating behaviour. Males and females reach sexual maturity a year after their birth.
In Britain all bat species and their roosts are legally protected, by both domestic and international legislation.
Many thanks to the Bat Conservation Trust for sharing this information; for more detailed reading please visit their website below.