8310 Caves not open to the public
Description and ecological characteristics
Caves are formed by the erosion of soluble rocks, such as limestones. They typically form the subterranean components of a distinctive ‘karst’ landscape, and are associated with various topographic features, including gorges, dry valleys, 8240 Limestone pavements, and dolines (surface depressions and hollows). Caves not open to the public is interpreted as referring to natural caves which are not routinely exploited for tourism, and which host specialist or endemic cave species or support important populations of Annex II species.
Caves lack natural illumination, and therefore support species which are adapted to living in the dark. Microclimatic conditions vary widely within and between caves, and this determines the composition of the fauna and flora. Many species feed on detritus derived from the surface; others are carnivorous. Cave-dwelling species (cavernicoles) can be divided into three categories:
- Troglobites – obligate cave-dwellers which typically display morphological adaptations, such as reduced pigmentation and regressed eyes.
- Troglophiles – facultative cave-dwellers which may have permanent populations in caves but which are also found in other suitable habitats.
- Trogloxenes – species which are found in caves but only for part of their life cycle.
The cavernicolous flora and fauna of the UK and other parts of northern Europe is highly impoverished compared to southern Europe. The reason for this is that most karst areas in the UK (except for parts of southern England) were glaciated during the Pleistocene, and many species are therefore recent colonists. Southern Europe escaped glaciation and consequently has a richer fauna of highly-specialised relict troglobites.
Cavernicoles in the UK include bacteria, algae, fungi and various groups of invertebrates (e.g. insects, spiders and crustaceans). Characteristic troglobites and troglophiles include Porrhoma rosenhaueri (a blind cave spider), Trechus micros (a ground beetle), Niphargus glennei (an amphipod, only known from Devon in the UK), and Arrhopalites pygmaeus (a springtail). Some caves are important hibernation sites for bat species, including all four Annex II species found in the UK.
European status and distribution
Caves not open to the public are widely distributed in Europe but are most frequent in the extensive limestone regions of southern Europe. The cavernicolous fauna of southern European caves includes a large number of troglobites, many of which are endemics. Notable species include amphibians, such as the blind cave salamander Proteus anguinus. An assessment of the occurrence and protection of the habitat throughout Europe was provided by Juberthie (1995).
UK status and distribution
In the UK, caves are particularly characteristic of the limestone areas of the North Pennines, the Peak District, the Mendips, south Wales, and County Fermanagh. Examples also occur in Devon, north Wales and Scotland.
Click here view UK distribution of this species
SACs where this Annex I habitat is a qualifying feature, but not a primary reason for site selection
- Limestone Coast of South West Wales/ Arfordir Calchfaen de Orllewin Cymru East Wales, West Wales and The Valleys
- Mells Valley Dorset and Somerset
- Mendip Limestone Grasslands Dorset and Somerset, Gloucestershire, Wiltshire and Bristol/Bath area
- North Somerset and Mendip Bats Dorset and Somerset, Gloucestershire, Wiltshire and Bristol/Bath area
- South Hams Devon
- Usk Bat Sites/ Safleoedd Ystlumod Wysg East Wales, West Wales and The Valleys
Many designated sites are on private land: the listing of a site in these pages does not imply any right of public access.
Please note that the map shows sites where the presence of a feature is classed as ‘grade d’, but these sites are not listed. This is because ‘grade d’ indicates a non-significant presence.