Leisler's bat
Nyctalus leisleri
The Leisler's bat is similar to the noctule, but smaller, with longer fur, particularly around the shoulders and the upper back, giving a lion's-mane appearance. It was formerly known as the hairy-armed bat. Adults have fur that appears golden-tipped or rufous-brown, the hairs becoming distinctly darker at the base. As with the noctule, the tragus (the lobe inside the ear) has a broadly rounded tip - it is almost mushroom-shaped.
Bat Facts
|
Description | |||
| Head and body length |
50 - 70 mm | ||
| Forearm length | 38 - 47mm | ||
| Wingspan |
260 - 320mm ( | ||
| Weight |
12 - 20 g | ||
| Colour |
Fur golden-tipped or rufous-brown, darker at base. | ||
|
Life cycle | |||
| Mating period | End August - October. | ||
|
Maternity colonies |
Established late spring. Young: usually one, born mid-June. | ||
|
Colony size |
20 - 50 bats | ||
| Longevity |
Up to 16 years | ||
| Habitat and food | |||
|
Summer roosts |
Tree-holes, bat boxes, buildings. | ||
| Winter roosts | Tree-holes, buildings, occasionally caves and tunnels. | ||
|
Feeding habitat |
Open deciduous and coniferous woodland, parkland, suburban areas and around street lamps. | ||
|
Food | |||
| Flies |
moths |
caddis-flies |
beetles |
Leisler's bats appear early in the evening, soon after the noctule, and have been observed emerging from houses at about sunset. They may stay away from the roost until dawn They usually fly high and fast in the open, frequently at or below tree top level, with shallow dives. Sometimes they fly close to the ground along lanes and well-lit roads.
Breeding
Mating occurs from late summer until mid-autumn. Breeding males emerge from their holes at dusk and slowly fly around calling loudly every second or so. They keep within 300 m of their mating roost, returning to the roost after several minutes, where they continue to call and await the arrival of females. If no females arrive, the males fly around calling again. These calls are audible to the human ear and are not the calls used in echolocation. The males do not feed during the courtship period.
Male Leisler's bats can have a harem of up to nine females; males give off a strong, sweet odour during the autumn.
In the summer maternity colonies of females gather in tree holes and sometimes in buildings, particularly in Ireland where colonies may reach 1000. The young are born in mid-June. Usually a single young is born, but twins are recorded more frequently in eastern Europe.
Summer roosts
Leisler's bat is naturally a forest bat, roosting in tree-holes for which bat boxes have proved in some areas to be a useful substitute. They occasionally share roosts with noctules and pipistrelles. They also roost in buildings, both old and new. In houses they have been found around the gable end in lofts, between tiles and underfelt, under ridge tiles, above large soffit boards, behind hanging tiles, under loft floor insulation, behind window shutters and in disused chimneys.
Leisler's bat is a mobile species and one roost is often occupied for only a few days before the colony moves to another roost. The bats are very vocal prior to emergence and are particularly noisy on hot summer days, producing a loud, metallic-sounding call.
Winter roosts
Leisler's bats hibernate in tree holes, in the cracks and cavities of buildings and occasionally in caves and tunnels. Elsewhere in Europe they sometimes hibernate in large groups in rock crevices.
Ultrasound
Leisler's bats' echolocation calls range from 15 - 45 kHz and peak at 25 kHz. The calls are occasionally audible to the human ear. On a bat detector a characteristic 'chip chop' with clicks at the top of the range is heard, but the sounds are less strident than those of the noctule bat.
Status and distribution
Leisler's bat is widespread but rare in Europe, including the British Isles, Isle of Man north to southern Scotland. A European stronghold is Ireland, where the species is the third most common bat and where the noctule does not occur. It is migratory in Europe with a record of 810 km. One British individual was found 250 km (157 miles) from where it had been ringed four years previously. It has also been found as a vagrant to the Shetland Islands.
Conservation
In view of its rarity in Britain all known roosts are important and special care should be taken of roosts in buildings and of wooded areas where the species is known to occur. Bat boxes have been successful in encouraging the species in some areas. The internationally important population in Ireland deserves special attention.
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