Lead Partner: Noel Jackson – Durham Bat Group
- Maintain and enhance the range and population size of all bat species within the Durham BAP area
- Protect, maintain and enhance habitat features required by bats
- Create habitat networks which reconnect appropriate habitats and provide linear features such as hedgerows as navigational corridors between foraging and roosting habitats.
- Increase awareness and implementation of the legislation that protects bats in the UK.
- Encourage greater understanding amongst professionals such as planners, developers, builders, building regulators and engineers, of bat ecology and conservation
- Increase public awareness and participation in bat conservation.
- Increase research, survey and monitoring work into current bat populations and trends.
The distribution of bats is concentrated along the woodland of the three main river corridors, the Derwent, the Wear and the Tees. The movement of bats from one valley to another is somewhat restricted by topography as well as intensive agriculture and industry. This makes known habitat corridors between river valleys particularly important.
There are eleven species of bat known to occur in County Durham, of which eight are known to breed:
Common pipistrelles are found on modern housing estates and are ubiquitous throughout the whole of the DBAP area.
Soprano pipistrelles are known to occur on the Tees, Wear and Derwent but are probably more widespread.
Noctule bats are localised in the area’s mature woodland, in rural areas.
Brown long-eared bats are reasonably widespread, but localised. They require large undisturbed roof spaces within flying distance of suitable woods.
Whiskered bats are fairly widespread but localized. Roosts in the Durham area are of national importance.
Brandt’s bat is much rarer and the roosts in the Durham area are of national importance.
Natterer’s bats roost in trees and large roof spaces, where they can warm up before leaving; this is one of Durham’s rarer species.
Daubenton’s bats are widespread along water courses and near water bodies throught the region.
Nathusius’ pipistrelle have been recorded feeding over the Tees at Cotherstone, near Bowes and near Whitworth on the Wear, but no roost sites are known.
Other species recorded are as follows:
Serotine bat (Eptesicus serotinus) – bat detector records only – probably animals indulging in post-breeding dispersal.
Leisler’s bat (Nyctalus leisleri) – Three bat detector records in 2000 only – nearest known breeding site near Sheffield.
Levels of knowledge concerning bats vary widely between different regions of the UK. Consequently, it is difficult to assess the relative health of Durham’s bat populations. Also of relevance is the fact that the only information available about bats is comparatively recent. Bats have only been surveyed since 1981 and the first quantitative survey of bats was completed in 2000. Therefore, the database is limited.
Much of what is known about bats in the Durham area comes from the work of the Durham Bat Group. Enquiries from householders with regard to bats in and around their properties are an important source of information on the bats in the DBAP area. However species which do not use built structures are probably under recorded. For example Daubenton’s bats can be seen and heard feeding over many stretches of inland water but relatively few roost sites are known. Natterer’s bats roosts are difficult to locate but bat detectors surveys suggest that this species may be present in a number of woodland areas.
Underground sites, whether natural or man-made, are important hibernacula sites in Europe. Surveys of similar sites in the Durham area have revealed only small numbers of visible animals. Though numerous pipistrelle summer roost sites are known, many with 100-200 bats present, only two winter hibernation roosts are known. One of these has up to 100 individuals present. However a lack of information about pipistrelle roosts across the UK makes it difficult to assess this in a national context.
- Habitat loss – decreasing areas of deciduous woodland, hedgerows, wetlands and grasslands reduce the availability of feeding and roosting sites. Loss and drainage of wetlands and inappropriate riparian management leads to loss of feeding and roosting areas. Undeveloped land which does not meet the standards for designation as SSSIs or Local Sites probably forms the bulk of bats’ foraging areas.
- Habitat fragmentation – the presence of linear features and wildlife corridors such as hedgerows and former railway lines between habitats can reduce the impact of fragmentation.
- Disturbance – disturbance in the summer may lead to the abandonment of young. Disturbance in the winter may arouse hibernating bats and force them to use up essential food reserves too quickly, with fatal consequences.
- Tree felling and tidying of dead/hollow trees – all bat species, and particularly noctules, will use hollow trees for both summer and winter roosting.
- Intensification of agriculture – this has led to the loss of high-quality feeding habitat as well as a reduction in insect biomass through the widespread use of pesticides. Larger bat species, such as the noctule, prey on larger invertebrates, especially large beetles and moths, which are now present in considerably reduced numbers. Cattle treatments for internal parasites using anthelmintics and the use of synthetic pyrethroid sheep dips have also contributed to this reduction in invertebrate numbers.
- Lack of awareness – there is a tendency for the needs of bats to be under-emphasised during the planning process. Listed Building Consent – consent for alteration and structural works on Listed Buildings can be obtained from Government Office North East (GONE) without the need for planning permission (which would be required for non-listed buildings). There is, at present, no monitoring system for this at GONE.
- Development – the loss of rear gardens to small scale housing developments results in habitat loss and reduces the structural diversity of foraging habitats for bats. Development of brownfield land is likely to lead to further habitat loss for bats.
- Refurbishment and demolition of man-made structures and buildings – roost sites in cellars, roof spaces and under eaves in buildings are lost through building maintenance, renovation and the installation of cavity wall insulation. It is now thought that bats may use cavity walls as hibernation roost sites. Bats have very specific roost requirements, such as bridges for Daubenton’s bats- it cannot be assumed that they will relocate to another apparently suitable site if a roost site is destroyed.
- Remedial timber treatment – these can be poisonous to bats. Because of their communal nature, entire roosts may be lost due to insensitive timber treatment exercises. Lindane, a chemical that was widely used in the past, has been implicated in the eradication of entire bat colonies. Treatments carried out during the 1980s are still toxic today.
- Recreation – there is a potential negative impact upon bats in crevices on cliff faces from climbers.
- Cavers and mine reseachers – these activities disturb hibernating bats in the winter and may also have an adverse effect in the autumn when the bats are swarming.
- Persecution, intolerance of, and a lack of understanding of the protection afforded to bats. Many householders are unwilling to host a bat roost in their homes because of misunderstandings with regard to the nature of the bats themselves and their perceived impact on their surroundings, particularly with regard to noise and droppings.
- Ineffective wildlife legislation and enforcement, combined with a lack of common knowledge regarding legislation.
- Cat predation – a significant number of bats are killed or injured by domestic cats.
- Lack of knowledge – the extent of losses to bat populations due to destruction or exclusion from roosts are hard to quantify because knowledge of roost locations is so limited. Very little is known about the locations of winter hibernation roosts.
- Climate change – the UK climate is predicted to change, which is likely to have an effect on bats in both the summer and winter.
- Wind turbines – have been shown to cause death to bats and have potential to cause damage to bats if inappropriately sited.
- Changes to external lighting may pose a threat to existing and potential bat roosts.