Bats and the places they roost are strictly protected by UK and European law. Bats use buildings, structures and trees for roosting and hedgerows, gardens, grassland, woodland and open water for foraging and commuting. For these reasons surveys for bats are required on most sites.
The scope of the bat surveys will generally be determined by the Preliminary Ecological Appraisal, but typically bat roosting surveys and bat activity surveys are required to meet the Bat Conservation Trust survey guidelines.
Where a building, structure or tree has been assessed as having the potential to support roosting bats, then further surveys are required to determine whether bats do actually use them as roosts. These surveys normally involve a surveyor watching the potential roost site at dusk and dawn to record any bats leaving or returning to a roost. Bat roosting surveys can only be conducted between May and September and multiple visits should be spread across the survey season. Where a bat roost is identified further surveys may be required to support a licence application if the roost is to be impacted by the scheme.
Bat activity surveys are required where areas of good quality bat foraging or commuting habitats will be adversely impacted by the proposed scheme. Bat activity surveys aim to identify which species of bats use the area, how they use it and in what numbers. The data is collected by experienced ecologists walking the site at dawn and dusk and recording all bats present. Additional data can be collected by instating static bat detectors around the site. These detectors are programmed to record all bat activity between dusk and dawn over several months and are useful for identifying some of the less common species of bats that may not be present during the transect surveys. Bat activity surveys can be undertaken during the bat active season which is April-October.