Earlier this year, Acer Ecology was commissioned to carried out bat surveys of a property near Monmouth. The property in question was an unoccupied, two-storey cottage, that was being used primarily as a storage facility. The property was located in an area classified as high-quality habitat. This means that the habitat around the property is very likely to be used by bats and is well connected to the wider landscape. Most bats prefer dark, unlit places with an abundance of insects, such as in woodlands, along the lines of trees/hedgerows, grazed parkland or along tree-lined river watercourses. The proposed works to be carried out on this building were renovation and refurbishment with the addition of an extension.
The preliminary roost inspection and emergence/ re-entry surveys discovered a variety of bat species resident in the property. Multiple species of bat were found on site: soprano pipistrelle, whiskered/Brandt’s bat and the lesser horseshoe. Acer Ecology’s main objective during this project was to determine whether the works to the property would cause the bats harm, to minimize the project’s impact and to create mitigation that would benefit both the bats and the owner. As bats were found to be using the cottage, works were undertaken under an European Protected Species (EPS) licence.
Did you know?
Soprano pipistrelle (Pipistrellus pygmaeus)
Soprano pipistrelles are one of the most common bat species identified throughout the UK. Soprano pipistrelles are notorious crevice-dwellers. They will roost between roofing tiles, inside soffit boxes behind fascias or bargeboards, inside roofing felt and even within the cavities between walls. Alternatively, they can roost in trees and caves. However, their increasing reliance on buildings for roosting has caused them to become vulnerable when drastic changes occur to a property that has a roost identified within it. (Image Credit: John Purvis on Visual Hunt)
Whiskered and Brandt’s bats (Myotis mystacinus and Myotis brandtii)
Whiskered and Brandt’s bats are also known to be crevice-dwellers, exactly like the soprano pipistrelle. Both species are closely related and are classified as vulnerable, and in some places in the UK are classified as scarce. These two species are difficult to tell apart. Whiskered and Brandt’s bats tend to roost together in both new and old buildings and are also known to share their roosts with other crevice-dweller species. (Image credit: Dellfalconer on Visual hunt)
Lesser horseshoe bats (Rhinolophus hipposideros)
Lesser horseshoe bats are one of the rarest bats in the UK. As a result, monitoring and promoting their survival is of the utmost importance to try and preserve this species. Lesser horseshoe bats use hedgerows and woodlands as their highways and feeding grounds. Their roost preferences include caves and old buildings, and they like to hibernate in mines and old cellars. These bats like a wide entrance to their roost sites for easy access, and once inside, they will hang freely.
Before proposed works
Bat boxes were placed on a suitable tree within the site to provide alternative roosting areas during the construction period. These boxes were suitable for the crevice-dwelling species found roosting in the cottage (soprano pipistrelles and the whiskered/Brandt’s bats).
However, the bat boxes are unsuitable for lesser horseshoe bats. Therefore, a stand-alone night roost was constructed before works began to provide an alternative roosting area
A licenced bat worker notified the building contractors of the bats and were made aware of the mitigation being put in place. The bat specialist also supervised of the removal of roofing materials.
Bat Mitigation
Soprano and Whiskered/Brandt’s Bat Roosts
The mitigation provided for the soprano pipistrelle and whiskered/Brandt’s bat roosts consisted of a raised ridge tile with access points with a roosting space beneath. Raised fascia boards were also installed, allowing bats to roost underneath them. External lighting was directed away from all bat roosts, their access points and flight paths. The roof was lined with traditional hessian reinforced bitumastic felt. Modern breathable membranes were not used, due to the highly damaging effect these can have on bat roosts. More information on this can be found in our article on breathable membranes.
Lesser Horseshoe Bat Roosts
The standalone night roost for the lesser horseshoes was retained. This had a letter-box style entrance slow (300mm by 200mm), and was constructed from plywood/rough marine ply and lined with traditional bitumen felt. Droppings from the previous roost were scattered around the entrance of the new roost to encourage the lesser horseshoe bats to relocate.
Post-Construction Period
After the bat mitigation was put in place, further improvements to the site are required to encourage the bats to remain on the site. This includes plans to improve the landscaping and replanting around the building to benefit the bat’s foraging and commuting habits.
Post-Construction Monitoring
Monitoring of this site has been ongoing since completion of the works to the cottage. This will continue for up to three years, with regular checks to be undertaken to ensure the integrity of the night roosts, and to keep the maintenance up-to-date to retain the roost in perpetuity. This is a prime example of a well implemented bat mitigation project undertaken by Acer Ecology in partnership with the owners, with the outcome in the interest of both the owners and the bats!
Bat Survey Information I Need a Bat Survey Bat Mitigation Guide
Bridgend – Mitigation Success! Forest of Dean – Bat Mitigation Project
