One of Europe’s rarest bats, the barbastelle is found across southern Britain, but only in low numbers.
Its large thick black ears and squashed face, together with its black fur, make the barbastelle easy to identify at close quarters. The ears are joined at the base by a thin flap of skin. The tips of the dark fur are paler, giving the bat a ‘frosted’ look. It is a medium-sized bat, weighing up to 13 g and with a wing span of about 90 mm. The broad wings allow the bat to fly slowly in open woodland, often close to water, searching for small moths. The slow and erratic flight can be another useful identifying clue, the bat often appears to hesitate in flight, almost hovering. Barbastelles use very quiet echolocation calls, best heard at around 32kHz, described as short hard ‘smacks’.
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Barbastelles have been recorded migrating distance of over 100 km in Europe, even in Britain they may still fly 20 km from their roost to feed. The small teeth and weak jaw of the barbastelle mean it cannot eat larger insects or beetles with tough wing cases.
The rarity of this little-studied bat, and its predilection for roosting in small colonies in trees, make it very difficult to track. The quiet echolocation call also make it difficult to trace barbastelles when they are hunting so that most animals are only identified during hibernation roost checks.
© Neil Reeves
Barbastelles are strongly associated with woodland. Most roosts that have been identified are in old trees, rather than buildings, and barbastelles seem to be reliant on ancient woodland and so are vulnerable to forestry operations.
During the summer they may fly
considerable distances to feeding grounds, where they hunt primarily for small moths often over, or close to, water. The decline in moth populations in the UK over recent decades may be having a significant effect on the barbastelle. As the weather cools they take a more diverse diet of flies, spiders and earwigs. When barbastelles are flying in relatively light conditions they may use sight and the noises emitted by their prey to hunt by, rather than echolocation. They seem to be more tolerant of low temperatures than other British bats and may not hibernate until very late in the year.
Hibernating barbastelles have been found in large trees, but also barns, tunnels and caves: some of the cooler hibernation sites. Barbastelles are often found roosting under loose tree bark during the spring and autumn. Individuals may use as many as 30 different roosts within their home range and fly up to 18 km from their roost to feed.
In the spring female barbastelles assemble in maternity roosts of about 20 individuals to produce their single pups. Males are rarely found within the maternity colonies and seem to roost alone, often in cracks in trees or behind flaps of bark. During the autumn single males, and up to half a dozen females, occupy mating roosts.
Barbastelles have been recorded living for up to 22 years. Barbastelles are less tolerant of disturbance than many other British bats, their dependence on large old trees for roosting, breeding, and hibernation can conflict with forestry priorities and attempts to tidy decaying or damaged trees. As a rare bat which hunts at a considerable distance from its roosts, the disturbance of a single roost can have significant impacts on its local distribution.
The barbastelle is widespread, but rare, in Cornwall, and found in suitable woodland habitat, mostly to the east of Truro. Elsewhere in the UK it occurs from the Midlands south, and also in southern Wales. It is found across central Europe from northern Spain to Russia.
Only a few barbastelle roosting sites have been identified in Britain, and two of these are in Cornwall. In 1998 one juvenile male barbastelle demonstrated its Cornish connections when it was found hanging on a wall in a pasty bakery in Callington.
Subject to the extensive legal protection of all British bats, the barbastelle is also included on both the UK and local BAPs. It has also been identified as globally threatened and declining.
Monitoring of summer maternity roosts and hibernation roosts by licensed bat workers. Mist net trapping by licensed bat workers. Emergence surveys. Bat detector monitoring. Cat kills and incidental reports.