The long-awaited fourth edition of the ‘Bat Surveys for Professional Ecologists: Good Practice Guidelines’ was published in September 2023. The intention is to update the guidelines every 5-7 years unless there are major changes to the legal protections for bats. The authors of the fourth edition focus on highlighting evidence gaps that exist and have made suggestions for areas for further research. For example, here are some adjustments:
Night Vision Aids
The utilization of Night Vision Aids (NVAs) has become of increasing importance within recent years. It is recommended that surveys should now be carried out using NVA’s as bats often emerge after it is too dark for the surveyors to observe them. It also gives the surveyor the chance to look back at the footage and give hard evidence whether there are any bats emerging or re-entering a structure/tree. At the time of writing, guidelines of the use of NVA’s for bat surveys are being developed.
Timing of activity surveys
There has also been a new adjustment to the previous survey guidelines, in relation to the timing between each survey. The minimum time between surveys is now three weeks apart, extended from two. This modification allows to provide a more comprehensive and representative sample of bat activity during the designated survey period.
Changes in dawn activity surveys
Activity surveys to determine the presence/likely absence of bat roosts has now been updated to only include dusk emergence surveys, with the elimination of the need for dawn-re-entry surveys. This is due to the risk of bats returning to their roosts early and being missed by the surveyor.
Changes to the guidelines for categorising the potential suitability of trees:
| Suitability | Description |
| PRF-I | PRF is only suitable for individual bats or very small numbers of bats either due to size or lack of suitable surrounding habitats |
| PRF-M | PRF is suitable for multiple bats and may therefore be used by a maternity colony. |
| Low roost suitability or PRF-I | Moderate roost suitability | High roost suitability or PRF-M |
| No further surveys required for trees | May to September, with at least one of the surveys between May and August | May to September, with at least two surveys between May and August |
No further presence/absence surveys are required for trees that have been assessed as having low suitability.
Static/Hibernation Surveys
Within the new guidance, automated/static surveys for winter activity now need to include the minimum of two weeks per survey each month from November to March, as opposed to December to February within the 2016 Bat Survey Guidance.
Previously, the survey effort for hibernation surveys were a minimum of two visits, one in mid-January and one in mid-February. However, the new guidance gives more flexibility with the possibility of the survey being carried out in December. Where necessary, this could also be adjusted for certain criteria such as; if very deep and inaccessible crevices are present; if bats are suspected to be hibernating but are absent at the time of the surveys; if the impact is predicted at a particular time; or if felt appropriate due to species-specific considerations.
Collins, J (ed) (2023) Bat Surveys for Professional Ecologists: Good Practice Guidelines (4rth edn). The Bat Conservation Trust, London.
