The village of Combe Down and its surrounding area plays host to an interesting diversity of plant and animal life.
Of Particular interest are the village bats, which include at least 10 different species. The area's stone-working past has provided an unusual man-made habitat that has been colonised or used in some way by these bats. Some bats use the mine for hibernating and as a maternity roost. The mines are likely in these ways since stone mining ceased. Because of this special conservation interest the stone mines form part of the Bath and Bradford on Avon Special Area of Conservation This is a protected wildlife site of European importance which supports about 19% of the UK's Greater Horseshoe bat population. In order for the mines' stabilisation scheme to go ahead these bat populations had to be safeguarded. Bath and North East Somerset Council worked closely with Natural England and several fully stabilised caverns have been created for the bats in the mines. Early indications suggest that these measures will be successful and help to retain these important bats in Combe Down.
Bat Pro was appointed as Bat Consultant to the project in February 2000. At that time the Byfield and Firs mines were known to be important sites for hibernating Greater and Lesser Horseshoe bats, and to provide roosting sites for a small maternity colony of Greater Horseshoe bats. Hibernating Greater Horseshoe bat numbers were known to be dwindling, whereas Lesser Horseshoe numbers were rising at that time and the status of the Greater Horseshoe maternity colony was poorly understood. In addition the level and times of use by the non-Horseshoe bats - collectively called the Vespertilionid bats - was unknown. Before engineering stabilisation works could proceed, the full use of the mines by all bat species had to be assessed and bat licences permitting work to proceed had to be obtained from Natural England.
The initial requirement was to devise appropriate surveys to assess and check the use of the mines by all types of bats throughout each year. In addition, there was a need to identify the distribution and quality of foraging areas and night roosts used by Greater Horseshoe bats, the only ones believed to breed underground. This was done by a radio-tracking study of 26 bats in summer 2000, and dietary analyses of dropping samples collected in trays beneath the summer colony. Finally, other mines near Shaft Road were also surveyed, so that complete baseline data sets were achieved for the local bat populations.Back to Top
The Greater Horseshoe bat (Rhinolophus Ferrumequinum) lives within the mines complex at Combe Down. Within the United Kingdom they are found mainly in the South West of England and South Wales although in recent years the British population has declined and is very fragmented. In 1995 the British pre-breeding population was estimated to be around 4000. The greater Horseshoe bat is on the verge of becoming a threatened species worldwide and is classified as Endangered within Europe.
They are buff in colour although older adults may be darker and reddish while females may be chestnut brown. The young are pale grey. They are covered in fluffy fur and are easily identified by a horseshoe shaped flap of skin surrounding the nostrils.
The bat mates from autumn to spring but mainly in late September or October. One young is born between mid-June to the end of July, occasionally in August. Greater Horseshoe bats are the longest lived of any European bat. The maximum age of a Horseshoe bat recorded in Europe is 30 years.Back to Top
In summer the bat roosts with its offspring in old buildings. Nursery roosts can contain up to 200 females. Greater Horseshoe bats wrap their wings around their body and hang freely by their feet either with their offspring or in small groups. Adult males can be found in the nursery roosts but leave when the young are born in mid-summer. In winter they hibernate from September/October through to April in warmer regions of caves or similar environments the exact timing depends on the weather and the availability of food. Breeding females tend to hibernate before other individuals. They hang freely from the roof with males found either singly or in dense groups of up to 300. Adult females tend to be solitary in winter. Hibernation is interrupted between once a day and once every 6-10 days depending on the temperature and the time of year to feed near the cave entrance or to change roost site. Females return to the same winter roost each year.Back to Top
Their preferred habitat is in areas of mixed deciduous woodland and grazing pasture on steep south-facing slopes. They live in caves and similar environments in habitats with scrub and open trees away from human disturbance. They need a series of caves in order to have a variety of temperatures and air-flow patterns.Back to Top
The Lesser Horseshoe bat (Rhinolophus hipposideros) is another resident of the Combe Down area. Much smaller than the Greater Horseshoe bat they weigh only 5-9g compared with 13-34g. In appearance they tend to be covered in a long, pale greyish brown fur although youngsters are a darker grey. It can also be distinguished from the Greater Horseshoe by its size.
A single young is born between June and July. On average they live for around four years although in Europe one specimen was recorded at 21.Back to Top
They are distributed throughout the South West of England and in most of Wales however their populations tend to be localised so they are still rare. They like sheltered valleys, woodland edge, pasture and Wetlands. It is the loss of their foraging habitat that may be responsible for their declining numbers.
In Europe nursery roosts are found from April to October. They usually contain 30-70 females but occasionally as many as 200 may be present. Females frequently change their roosts during the summer months, showing a preference for roosts that can be accessed by interrupted flight. They like to roost in warm buildings like attics or boiler rooms and cave-like environments. They hang freely by their feet in warm sites with abundant food or in clusters of up to 150 in colder roosts. Here they hang with their wings wrapped around their bodies.
In winter they hibernate from October through to April and are active during the day in spring and autumn. They roost in caves or similar environments, hanging freely high above the ground although they can be found in the lower crevices. Groups may be close together but clusters do not occur.
In 1995 the pre-breeding population was estimated at 14,000 divided equally between England and Wales. In the last 50 years lesser horseshoe bats have become extinct in the north midlands and northern England.Back to Top