Species Bechstein’s Bat

Facts about Bechstein’s bats

English name: Bechstein's bat
Scientific Name: Myotis bechsteinii
Number of young: One born late June to late July
Diet: Moths, beetles, spiders and caterpillars
Habitat: Tree-dwelling species associated with old growth woodland

Distribution and status

Until the discovery of a maternity colony in 1998, Bechstein's bats had not been recorded breeding in Britain over the previous 150 years, reflecting the difficulty of surveying for rare woodland bats. In recent years, new techniques have been developed, particularly the use of acoustic lures, which attract bats into mist nets and harp traps. Using this method, Britain’s population of 28,000 Bechstein’s bats has been recorded in southern England from Gloucestershire to Sussex, and has been found breeding as far north as Herefordshire and Worcestershire. There are also recent records from Kent. Bechstein’s bat does not occur in Ireland.

Identification

The most distinctive feature of Bechstein’s bat is its long ears that are, with the exception of the two long-eared species, the largest among the British bats.

Bechstein's bat is a medium-sized bat with a pink face and a pointed fox-like snout. It has light to reddish-brown fur above and pale fur underneath. Bechstein's bats are associated with mature woodland with fossil records showing that it was common before the ancient wildwoods were cleared for agriculture. It is now one of our rarest bats.

Bechstein's bat ©Daniel Hargreaves

Habitat and roosts

The roosts of Bechstein’s bat are most strongly associated with woodland or hedgerow trees, particularly oak and beech trees. Very occasionally the species roosts in buildings.

Roosts are typically within old woodpecker holes, rot holes or hollow dead branches in large, old deciduous trees. During the summer, Bechstein’s bat readily uses bat boxes made from cement and sawdust in preference to traditional wooden boxes. Evidence from mainland Europe suggests that it roosts deep in cracks in caves and mines. Therefore, the small numbers of observable animals in such sites in Britain may be just the tip of the iceberg. It is also likely that Bechstein’s bat overwinters in tree hollows. This species switches roosts often and a colony can use as many as 60 roosts in a single breeding season.

Diet

There have been few studies of the diet of Bechstein’s bat in Britain, but research in mainland Europe suggests that it has varied diet including moths, beetles, spiders and caterpillars.

Bechstein’s bat mainly forages in areas of closed-canopy woodland close to water. It has also been recorded foraging along overgrown hedgerows and tree-lines. These areas are usually located within 1km of the day roost used by a colony. Individual bats select a favoured tree or group of trees to which they return repeatedly when foraging. Bechstein’s bat hunts throughout the vertical woodland layers, from tree canopy to woodland floor, taking prey on the wing or gleaning insects off vegetation. It may also feed by hanging onto foliage and flying out to retrieve passing insects.

Breeding

Mating activity occurs during late autumn and early winter when the bats swarm at underground sites and males and females from multiple colonies interact and mating occurs — but, as with all bats, the females stores the sperm until spring.

Ringing studies have shown that Bechstein’s bat can live up to 23 years, although the average lifespan is much less.

In spring, following hibernation, pregnant females gather in maternity colonies in tree cavities. A colony of up to 80 bats may use about 60 different tree cavity roosts within a small area, moving to a new site every few days. Although at times the entire colony may occupy a single tree, it typically breaks up into smaller subgroups to roost in different trees. During pregnancy, females may be joined by small numbers of adult males. These males leave once the females have given birth to their single babies between late June and late July. The young bats are weaned at about four weeks old but do not become sexually mature until one or sometimes two years old.

Threats

Most bat species face the same sorts of threats — primarily habitat loss and use of pesticides.

Habitat loss includes drainage of wetlands, woodland clearance, intensification of agriculture, including the increased use of pesticides, resulting in the loss of roosting sites and reductions in the abundance and diversity of their insect prey. Bats’ colonial habits and their reliance on buildings for roosting also make them vulnerable to building repair work, re-roofing and the use of toxic timber treatment chemicals.

In Britain and Ireland, all bats and their roosts are fully protected by law. It is an offence to disturb or kill bats and to destroy or alter their roosts in any way without first consulting the appropriate statutory body.

Bechstein's bats prefer old growth woodland.

VWT's work

VWT carried out the first radio-telemetry studies on the species in Britain during the mid-1990s to determine the habitat preferences of this species. The study colony was in a bat box scheme in a deciduous lowland woodland in Dorset and the results of the research showed that this species feeds in closed canopy broadleaf woodland with a well-developed understorey often close to water bodies. During the summer, females rarely travel more than a kilometre from their day roosts.

The same colony has been the subject of a long-term ringing study to establish its colony size, breeding success and colony dynamics.

The Trust worked in collaboration with the University of Sussex to assess the genetic diversity and structure of the British population of Bechstein’s bats, and to develop a method to estimate the age of individual bats.