It has ears almost as long as its body. While resting, it folds these and hides them under its wing, leaving only the pointed tragus visible. This feature distinguishes it at a glance from most European bats, long before any ultrasound detector is needed.
It hunts by whispering, using echolocation pulses so soft they are barely detectable at a distance. This strategy allows it to go unnoticed by the extremely fine hearing of the moths it feeds on, which it often collects directly from a leaf or branch.
It shares almost everything, including this very particular behaviour, with its more southerly relative. Where both species occur, they are practically impossible to differentiate by either appearance or sound.
The Brown Long-eared Bat is a small to medium-sized bat. It is unmistakable due to its enormous ears, which are almost as long as its body and joined at the base. When at rest, it folds these ears under its wings, leaving the tragus visible. Its fur is a warmer brown than that of its southern relative. It can be confused with the Grey Long-eared Bat, which has somewhat colder-toned fur and a slightly shorter muzzle. Reliable separation between the two often requires examining details of the penis or skull.
Peak energy frequency between 25 and 50 kHz, with a downward sweep. It emits a very low intensity FM-type pulse, making it a 'whispering' bat. On the detector screen, this produces a weak, short trace, easily missed unless very close to the animal. Duration 2-5 milliseconds long. It cannot be reliably separated from its southern relative by sonogram, as both species share a very similar whispering call pattern. The exact species should not be assumed based on sound alone. Beneath feeding perches, often inside buildings such as attics, shed moth wings with a characteristic cut and fine, granular guano accumulate. The Brown Long-eared Bat emerges relatively late after sunset, with a slow, highly manoeuvrable flight close to vegetation.
Deciduous and mixed woodland with well-developed undergrowth, sheltering in tree hollows, attics and building crevices, from lowlands to mid-mountain areas. Distributed throughout much of Europe, with a presence extending into parts of Asia, in a more northerly area than that of its southern relative.
Insectivorous, specialised in moths, which it locates largely by hearing rather than by active echolocation, often picking them up directly from vegetation.
The Brown Long-eared Bat forms small breeding colonies in tree hollows or human constructions, and is very sensitive to disturbance in its breeding and hibernation roosts. Its slow flight and whispering echolocation allow it to pass close to vegetation without being detected by the moths on which it feeds.
Populations are generally stable throughout most of its range, with no signs of widespread decline. However, locally the Brown Long-eared Bat may be affected by the loss of mature woodland with available tree hollows.
Loss of mature woodland with tree holes and of traditional attics used as breeding roosts, use of insecticides which reduces the availability of moths, and disturbance in hibernation roosts.
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