Barbastelle

head of barbastelle bat The Barbastelle (Barbastella barbastellus) is a very elusive bat with very few records from Britain each year. It is recorded from a wide area of southern Britain though it is very unpredictable in its occurrence and only 4 breeding colonies are known in the UK. It is also found in most of western Europe (excluding Scotland, Ireland and most of Scandinavia).

Distribution map for Barbastelle bats in Warwickshire. (Click for a full sized image)
Distribution map for Barbastelle bats in Warwickshire. (Click for a full sized image)

It is a medium-sized species with blackish fur on the back and the tips of the hairs may be pale cream or yellow, giving a frosted appearance. The underfur is grey-brown, often with pale tips. The ears are black, short and broad and joined across the forehead and with its rather squat face this gives it a very distinctive "pug-like" appearance.

Barbastelle bats are vulnerable to the decline of woodland, which results in the loss of suitable feeding habitats and hollow trees for roosting. They are susceptible to pesticides, especially those used as remedial timber treatment chemicals. Disturbance and vandalism of their hibernating sites, caves and tunnels, is an additional threat.

The latest news on the "Warwickshire Barbastelle Project" can be found on their Facebook page.

flight & ultrasound

Barbastelle bats emerge in early dusk and hunt low over water and at tree top height along woodland edges and gardens. They fly fast and skilfully, using a two-part call. The 43 kHz call is generally weak and often inaudible or absent. However, the main call is much louder and is lower in frequency, with a peak frequency around 32kHz. It is said to resemble a sort of "wood-block" sound. Their calls are very quiet being up to 100 times quieter than other aerial hawking bats which allows them to specialise in hunting for moths that can hear other bat species' calls. The downside of using these weaker calls is that they are unable to "see" as well as those bats emitting stronger calls.

barbastelle bat call  Barbastelle call on a Heterodyne bat detector

barbastelle bat call  Barbastelle call on a Time Expansion bat detector

breeding

In summer females segregate and form small maternity colonies; males usually remain solitary or in small groups. The females are sexually mature in their second year. Barbastelle bats are very sensitive to disturbance.

summer roosts

barbastelles roosting Roosts are mostly in hollow trees and buildings. Other recorded roost sites include under tree bark and amongst exposed tree roots.

winter roosts

In winter they occasionally appear close to the entrances of caves during prolonged cold spells. As they are a cold-resistant species, this suggests that they are not dependent on such underground sites but make use of them in periods of particularly cold weather. Winter groups are commonly of mixed-sex.

Description  
Head and Body Length 45 - 58 mm
Forearm Length 36 - 44 mm
Wingspan 260 - 290 mm
Weight 6 - 13 g
Colour Fur is blackish on the back and the tips of the hairs may be pale cream or yellow, giving a frosted appearance. Squat face gives a very distinctive 'pug-like' appearance.
   
Life Cycle  
Mating Period Autumn and winter.
Maternity Colonies Young: 1 born mid-June.
Colony Size 10 - 20 females, rarely up to 100.
Longevity 23 years.
UK Status Rare.
   
Habitat and Food  
Summer Roosts Hollow trees and buildings.
Winter Roosts Caves, tunnels, trees.
Feeding Habitat Wooded river valleys, over water and woodland edges.
Food Lepidoptera, diptera, small beetles. They have a weak jaw and so are unable to bite through the shells of large beetles.

further reading

'An aerial-hawking bat uses stealth echolocation to counter moth hearing' by Holger R. Goerlitz, Hannah M. ter Hofstede, Matt R. K. Zeale, Gareth Jones, Marc W. Holderied (Current Biology) (web page, 510Kb)

Detailed species notes on the Barbastelle by Jens Rydell & Wieslaw Bogdanowicz (American Society of Mammalogists, 1997) (pdf, 988Kb)