Rachel, Surveying, April 26
When conducting preliminary bat roost assessments (PRAs), we follow the Bat Conservation Trust guidelines for professional ecologists. The guidance dictates that buildings, structures and trees should be rated based on their potential suitability for roosting bats. This can mean that even without any evidence of bat use, or seeing any bats, features can need further survey.
Why do we need to categorise buildings?
The categories determine the extent of the additional survey effort needed to prove absence of roosting bats. For example, a negligible structure will not require any further surveys, whereas a moderately suitable structure requires at least two emergence surveys to prove absence.
See the handy table below for each category’s requirements:
| Recommendations | Low roost suitability | Moderate roost suitability | High roost suitability |
| Minimum number of surveys | One dusk emergence survey visit | Two separate dusk emergence survey visits* | Three separate dusk emergence survey visits* |
| Timing of surveys | May to August | May to September, with at least one of the surveys between May and August | May to September, with at least two of the surveys between May and August |
The window for surveying fills up well in advance every year, so get in touch to discuss your project requirement and get a survey quote as early as possible in your development timeline.