A Preliminary Roost Assessment, or PRA, is the initial scoping assessment of a building to record whether there is suitability for roosting bats. PRAs are needed to inform the requirements for further bat surveys, as part of the planning process. The aim of a PRA is to gather as much information about the site and the surrounding area as possible, so that the potential impacts of the proposed development on bats can be assessed. This is achieved through a three-part process: a desk study, a field survey, and an evaluation/impact assessment.
A desk study involves obtaining details of the landscape surrounding the site, so that the ecologist can assess both the likelihood of bats being present on site and the potential impacts of the development on ecologically important sites and habitats in the surrounding area. This study includes identifying Priority Habitats and Statutory Designated Sites within one kilometre of the site and previously-granted EPSLs (European Protected Species Licences) within two kilometres of the site. For example, an ancient woodland adjacent to the site would be incorporated into the desk study.
A field survey involves an ecologist with at least a Class 1 Bat Survey licence visiting the site to gain information on external or internal features of the building/structure that could potentially support roosting bats. The idea is to assess what level of suitability the building/structure has for summer roosting and winter hibernating bats. This involves surveyors inspecting the external parts of the building as well as the inside of any accessible roof spaces and taking note of any potential roosting features. Many of these features involve gaps the width of a finger that bats can squeeze into, such as lifted roof tiles and small gaps in timber frameworks. However, these are not the only features the ecologist is checking for; for example, they will also record any potential access points for bats into the roof void from the outside. Furthermore, the ecologist will look for any signs of bat activity, such as droppings and feeding remains. If droppings are found, a small sample will be collected by the surveyor, who will then send it off to the laboratory for analysis to determine the species. Permission from the landowner and a full risk assessment are required prior to the field survey.
With the information from the online data search and the field survey, the ecologist can then carry out the evaluation assessment of the building/structure for its suitability for roosting bats and whether the proposed development will have an impact on them. Here, the building/structure will be categorised as having either negligible, low, moderate, or high suitability for summer roosting and winter hibernating bats, as well as the wider site for foraging and commuting bats. If bats themselves or evidence of bats are found in the building/structure, then the building/structure is assessed as a confirmed roost for bats. The rationale for these categorisations is adapted from Collins J, 2016 Table 4.1 page 35 and ‘Assessing Sites for Hibernation Potential. A Practical Approach, including a Proposed Method & Supporting Notes’, Middleton, 2019. The assessment made is presented in a report and includes an evaluation of the potential impacts of development and whether any further survey work is required. The reports we write are in accordance with the up-to-date CIEEM guidelines for ecological report writing. If further surveys are required, then the results of these surveys and final assessments are required to inform the planning application. The ecological reports are valid for 12 months so must be submitted to inform a planning application within a year of the report being issued. An updated survey may be required if the report is not submitted in time. It is also worth noting that while PRAs can be completed at any time of year, further surveys for bats, which may be required have to be undertaken during survey season, i.e., from May until August/September.
To demonstrate how these studies come together to inform the PRA report, let’s take an example. For site A, the online data search includes records of multiple bat roosts present nearby and an ancient woodland (a habitat that is highly suited to supporting foraging, commuting, and roosting bats) adjacent to the site. During the field study, the ecologist found several potential roosting features, including extensive lifted roof tiles. The combined findings of the online data search and the field study will lead the ecologist to assess site A as having high suitability for summer roosting bats and for foraging and commuting bats. In this case, further survey for bats would be required, if the development is likely to result in an impact on bats. Further survey for bats is necessary because all bats and their roosts are fully protected under Schedule 5 of the Wildlife & Countryside Act 1981 (as amended) and the Conservation of Habitats and Species Regulations 2017 (as amended). Further survey may be recommended in the form of bat activity surveys, hibernation surveys, and/or dusk emergence and dawn re-entry surveys, depending on the findings of the PRA.