Bechstein’s Bat

Almost everyone will have seen bats flying overhead, catching food, on a summer’s evening. But not many people know about the Bechstein’s (Myotis bechsteinii), an elusive bat which may be one of the rarest mammals in Britain.

The Bechstein’s bat is restricted to central Southern England and South Wales, mostly living in old growth broadleaved woodland. Most individuals are found to roost in trees all year, unlike many other species that seek out houses or caves in the winter months. They feed on moths, other insects and spiders, which are often plucked from tree branches.

Conservationists estimate the UK population to be around 1,500, but no one is really sure how many there are. They seldom leave the canopy of the woodlands where they live, making them difficult to detect. However, the Somerset Bat Group have successfully uncovered several previously unknown Bechstein's breeding sites in the county.

Bat detectives

One of the main methods of identifying bats is by their vocalisations. Some bats have a distinct frequency at which they echolocate, which is dependent on the type of they hunt or what kind of habitat they are hunting in. A bat detector reveals the frequency of the calls and makes them audible to the human ear, so the species can be identified. However, this technique doesn’t work well for detecting Bechstein’s. They echolocate at a very similar frequency to other Myotis species and so they are close to impossible to distinguish from them.

To overcome the problem leading UK bat researchers have developed a ground-breaking technique to relay ultrasonic social calls to locate these very secretive bats. These calls elicit a territorial response in breeding female Bechstein’s bats. The bats are attracted to the source the simulated calls and can then be harmlessly caught in a specially designed net, a harp trap, identified and then released.

National Survey

The Bat Conservation Trust set up a 4-year Bechstein’s bat monitoring scheme, which started in 2007, to find out more about this secretive species. They are aiming to get a more accurate estimate of the number of Bechstein’s resident in England and Wales, and find out whether the population is increasing or decreasing. The information gathered will be used to help conserve areas where this rare mammal lives.

How you can get involved

The Somerset Bat Group joined the project this year, and members have been surveying for Bechstein’s in suitable woods in the county throughout the summer, including Somerset Wildlife Trust reserves. The group have found nine females and one male to date, and have also recorded many other species, including Lesser Horseshoe and Whiskered Bat.

The group will be completing the survey in May and June next year in the hope to identify even more colonies of Bechstein's. You can find out more about the group and how you can get involved with surveying for bats in the county here.

To find out more about the Bat Conservation Trust Bechstein’s project visit their website.

Author: Hannah Montag (SERC trainee)