When to Consider Advanced Bat Surveys

when to consider advanced bat surveys…

B.A.T. Ecological can assist with or lead your bat trapping and radio-tracking projects, and can provide experienced and licensed fieldworkers. Matt Cook of B.A.T. Ecological is a fully licensed expert in advanced bat survey techniques, including for the Natural England Bats in Churches Project - contact info@bat-ecological.co.uk | +44 (0) 7870 157022 for more information.

Advanced Licence Bat Survey Techniques - ALBST - involve catching bats using mist nets, harp traps and sometimes acoustic lures, and healthy bats may also be radio-tagged and radio-tracked to locate their roosts or where they forage. Bats are typically caught in flight away from their roosts using these methods, although in some circumstances they may also be caught exiting their roosts, or at the underground sites that some species ‘swarm’ at to mate in the spring or autumn.

All bats caught on advanced surveys are released as soon as they have been identified, classified and measured (processed), although depending on the study some bats may be fitted with a small (<5mm wide) forearm ring and / or have a tiny (<5g) radio-tag temporarily glued to their back, if they are being monitored or radio-tracked respectively. Catching bats and marking them in any way requires special advanced licences from either Natural England, Natural Resources Wales or Scottish Natural Heritage, and a high level of training is a pre-requisite for holding these kinds of licenses.

Bats are small, nocturnal and elusive, and it can be very hard to identify certain species. They are one of the most challenging groups of protected species to survey for in Europe when considering the impacts of development. Advanced bat survey techniques are therefore very useful for understanding exactly what bats use a site and how they use it. The more invasive nature of these methods does pose a small increased risk to the welfare of individual bats, and the surveys can also sometimes temporarily disturb bat behaviour. However, because these techniques are only employed by suitably trained and licensed people, the methods are only used where it is both ethical and effective to do so. The few experienced bat ecologists who use these methods will also be experts in identifying and classifying the bats they catch and ‘processing’ them as the study requires, and they will also understand each species’ autoecology.

With the above in mind, advanced bat survey techniques are a surprisingly cost-effective way of gathering high-level information on the bat assemblage at a given site, which therefore enables a more robust impact assessment in the context of (re)development-type activities. While advanced bat surveys are usually only required where non-invasive survey methods such as bat detecting cannot provide the required information, you should always at least discuss the suitability of these techniques for your project with an expert bat ecologist.

Chapter 9 in the current Bat Conservation Trust (BCT) Good Practice Survey Guidelines (2023) provides more information on ALBST including some good examples of where the use of advanced survey techniques is appropriate. Advanced bat surveys should be considered where there could be significant impacts from development type activities on woodland (including small areas), parkland, rivers, ponds and lakes, multiple mature deciduous trees / tree lines and established native hedgerows, meadows (including flood meadows) and pasture, church bat colonies, and potentially projects involving multiple or complex buildings and underground structures.

In particular, advanced bat surveys are usually preferable to inform the impact assessment of any proposed activity where barbastelle or horseshoe bats have been recorded on detectors, and / or where the presence of these species and Bechstein’s bat (which is harder to identify on detectors) is reasonably likely on or near the site. Knowledge of the species’ ecology and its distribution is essential to determine this likelihood, as is a comprehensive desk study to include consultations with local wildlife groups.

The above four bat species (and their habitats) require special attention in an impact assessment because they are afforded additional legal protection as ’Annex II species’ under the EU Habitats Regulations. Their scarcity also means they are considered conservation priority species. Similarly, although Alcathoe bat and / or the grey long-eared bat are not listed under Annex II of the Habitats Regulations, they are also nationally very rare. As such, and because they can easily be mistaken for the more common species within their respective genera, advanced surveys should also target these two species if a proposed (re)development site is reasonably likely to support them.

Occasionally, it may also be necessary to target other bat species via advanced bat surveys of proposed development sites, perhaps, for example, because certain species are a regional conservation priority and / or are regionally rare - an experienced bat ecologist, a robust desk study, and a strategic approach to acoustic surveys should provide a good platform for deciding what is required.

Advanced techniques can also be used to confirm the status of, and locate, bat roosts within buildings and other structures, and to assess the importance of underground sites for bats. Catching them means that the species sex, age class, and / or reproductive status can be confirmed for example, and roosts can be located if bats are radio-tagged. This then significantly augments the appraisal of the bat assemblage at the site, any impact assessment, and the design of any required mitigation and compensation strategy.

The Natural England ‘Bats in Churches Project’ is also employing advanced survey techniques at a handful of churches to help alleviate some of the issues caused by large colonies of bats in these historic buildings - Matt Cook of B.A.T. Ecological is one of only a handful of UK bat ecologists licensed to undertake this highly specialist work.

In addition to the useful information pertaining to advanced licensed bat surveys in the current (2023) BCT bat survey guidelines there are several publications that provide information on capturing and processing bats, including the JNCC Bat Workers Manual, 3rd Edition (2004), NE guidance note WML-G39 (Guidance on the capture and marking of bats under the authority of a Natural England licence), and Kunz and Parsons (eds.) (2009) Ecological and Behavioural Methods for the Study of Bats, 2nd Edition.

Please get in touch if you would like to discuss any of the above, or you need help with any bat surveys, reporting, licensing, or mitigation / compensation design and implementation: info@bat-ecological.co.uk | +44 (0) 7870 157022.