In late 2023, the Bat Conservation Trust (BCT) released updated industry standard guidelines for bat surveys; the 4th edition of the ‘Bat Surveys for Professional Ecologists Good Practice Guidelines’. Among the updates was an overhaul of the methodology for identifying bat activity levels on sites.
Often “ improvements” mean more costs, for example , through increased survey effort, more complex kit, more intensive data analysis, or more frequent site visits. This can be a bitter pill to swallow for developers and increase friction. However, after a season of implementation in 2024, at Ecology by Design, we feel that the updated guidelines are a significant improvement benefitting both developers and bats conservation.
Bat Surveys – the new best practice
Formerly called transect surveys, the 2023 methodology renamed the surveys Nighttime Bat Walkovers (NBW).
Previously, ecologists would have to walk a predetermined route at a constant pace from sunset until 2-3 hours afterwards, while recording bat activity observed during the walk. Often, these routes were supplemented by stopping at predetermined locations where the ecologists stood still for a short period of time to observe any hotspots of bat activity. However this methodology, while highly repeatable from one visit to another, did not allow for flexible monitoring where ecologists were allowed to follow actual flight activity, to identify roost locations for example.
Now the survey is split into two parts: 1) stationary observations and 2) mobile observations. For 0.5-1 hour after sunset, a pair of ecologists is stationed at habitats suspected of being highly valuable to local bat populations . The ecologists use this time to follow bats and investigate the areas with high activity levels to characterise the bat use of the site. The pair then roughly sticks to a predetermined route (3-5km) on site that captures bat use of the wider site but is advised to deviate from it to follow bats. It also acknowledges the advances made in technology in recent years, strongly promoting the use of night-vision aids, such as thermal imaging cameras, to record bat behaviour.
Key Changes
The guidelines are now clearly designed for ecological consultants.
The previous approach focused on survey repeatability (seven consistent visits), while now it focuses on site responsiveness (three flexible visits).
When clients are looking at a site for development, we often have a single survey season to determine the bat use of a site before informing them of potential impacts, designing mitigation and compensation, securing licences, etc. The malleable and responsive approach now allows for an investigation of the site that is more in line with industry needs.
Our Own Experience
Thankfully we have a large team of Level 1 and Level 2 bat licensed ecologists so were readily able to adapt our approach to meet the new brief.
Historically, we found transects were an effective way of understanding bats use of the landscape, however they were labour intensive and costly for clients. Their lack of flexibility was also an issue.
For example, in 2020 we had a proposed minerals extraction site which needed assessment. During one transect, several serotine bats were observed commuting from the north of the site soon after sunset, strongly indicating a roost in close proximity. Frustratingly, the survey guidelines at the time did not allow for deviation from the route, and we had to turn away from the flightline to continue with the survey. With the 2023 guidelines, the serotine roost could be explored to both accurately determine not just its location but also the type of roost, whether maternity, day or occasional.
Laura Grant, Associate Director said “When I first read the guidelines I was worried that the lack of consistency would make reporting on the findings a challenge, however, I am delighted with how the Nighttime Bat Walkovers have worked in practice. Activity levels within sites have been easier to assess and it’s enabled roosts to be found on a number of sites. For example, in 2024 commuting bats were observed when surveying farmland for a renewable energy project and we were able to backtrack in the direction of the observed commuting, resulting in discovery of a common pipistrelle day roost in a farmhouse which enabled refinement of the proposals to protect the roost.”
Benefits to Developers and Bats
The new guidelines allow for more accurate assessments of bats’ use of the landscape by giving greater flexibility and opportunity to identify roost sites. In doing so, more appropriate mitigation can be designed to ensure the protection and enhancement of roost sites, commuting routes and foraging areas.
For developers, these changes mean that robust data can be collected more cheaply in a reduced timeframe.
Supporting Your Projects with Expert Bat Surveys
Looking to progress your project while achieving excellent conservation results? Our experienced team of Level 1 and 2 bat licensed ecologists specialise in designing and conducting Nighttime Bat Walkover surveys. Get in touch today to see how our expertise can help move your project forward seamlessly. Contact us at hello@ecologybydesign.co.uk.
Jan 2025