Written by Cathryn Baillie (Project Officer), Bat Conservation Trust, February 2024
Executive summary
In 2023 we delivered a total of 59 bat surveys across all project areas using a series of monitoring techniques, including passive acoustic and in-person methodologies already utilised by the National Bat Monitoring Programme (NBMP). In total we have recorded at least seven of the nine species of bats verified within Scotland and contributed to the known species distribution in these areas.
Research has been undertaken to understand the species information already existing in the project areas and to pilot the passive acoustic monitoring programme with landowners on Skye. While our initial focus has been on Skye, we have worked with our project partners to initiate bespoke species monitoring strategies in Orkney, the Outer Hebrides and the Solway Coast.
“I’m delighted that a new bat group in the Outer Hebrides will join the existing network of 12 active Scottish bat groups…Thanks to this new group we will be able to collect more comprehensive data about bats in the Outer Hebrides” – Claudia Gebhardt, Scottish Bat Officer
1. Introduction
1.1 Project background
Species on the Edge is a four-and-a-half-year programme of work to conserve 37 vulnerable species on Scotland’s coast and islands. Protecting Scotland’s Island Wonders is one of nine species projects and is being led by Bat Conservation Trust (BCT).
1.2 Project aims
At least nine species of bat are found in Scotland, however there are some areas where we know very little about local bat populations. We are working to address this knowledge gap by increasing our monitoring efforts in several areas:
- Argyll and the Inner Hebrides
- The Outer Hebrides
- The Orkney Islands
- The Solway Coast
To ensure their future, we need to better understand the status of bats on our Scottish Islands and coastal areas. We aim to increase our knowledge of how bats face the challenges and maximise the opportunities that islands and coastal areas offer, through extensive monitoring.
This report summarises our monitoring efforts in year one.
The main survey aims:
- Increase bat records.
- Increase understanding of species’ status and distribution.
- Discover and monitor roosts.
- Identify key foraging areas.
- Identify key habitats and opportunities to enhance them.
2. Findings
2.1 Monitoring on Skye
2.1.1 Background
There are records of five species on Skye in the National Biodiversity Network database (NBN Atlas); the most frequently and recently recorded are common pipistrelle (Pipistrellus pipistrellus). Other species recorded include soprano pipistrelle (Pipistrellus pygmaeus), brown long-eared bat (Plecotus auritus) and Daubenton’s bat (Myotis daubentonii), with 2 records of noctule (Nyctalus noctule) from 2011.
2.1.2 Methodology
We used a mixture of passive acoustic monitoring (PAM) and in-person surveys to achieve our monitoring targets on Skye this year.
PAM:
AudioMoths (AMs) are static recording devices that can be programmed and left in the field to record sound files onto an SD card. Those sound files are then analysed by BCT’s sound classification system, and automatically given an ID, a selection of the results are then verified manually.
A total of 18 AMs were used to identify the presence of bat species, as well as key foraging and commuting areas. Our aim was to collaborate with local landowners and get good coverage of our project focal areas.
Six landowners participated in our PAM work, and we deployed between one and six AMs on each site, for a minimum of three nights. The devices were placed in a variety of habitats that had the potential to support our target species and were set to record from sunset to sunrise. AudioMoths were deployed during a weather window of appropriate conditions to try and ensure a fair and accurate representation of species and activity for each site.
In-person surveys:
This year we focussed on explorative surveys, either walking a transect through suitable habitat types, or following the methodology of the National Bat Monitoring Programme’s well-established Sunset and Waterways surveys.
Sunset Survey – Getting started – Bat Conservation Trust (bats.org.uk)
Waterway Survey – Explore NBMP Surveys – Bat Conservation Trust (bats.org.uk)
We used EchoMeter Touch 2 (full spectrum) and Magenta 5 (heterodyne) bat detectors for all our in-person surveys on Skye.
2.1.3 Findings
As expected, Pipistrellus spp. are the most recorded bats on the island. Of the 39 surveys all bar one recorded the presence of common pipistrelle, which implies that they are likely well distributed across the island. Soprano pipistrelles were also regularly recorded, being found in 16 of the surveys. We do not yet have enough information to draw conclusions on factors affecting the distribution of the species. All sites had features favourable for them, including areas of mature broadleaved woodland, availability of foraging sites, linear features and fresh water close by.
Other species were less frequently recorded, but we did have a new record of brown long-eared bat. The record was from an old church building, a structure type known to be used by the species. More work will be carried out in 2024 to understand if the structure is a roost site.
Two further records were made of a Myotis species. One record came from an AudioMoth positioned adjacent to a freshwater pool in an area of regenerating native woodland, within a recently felled spruce plantation. The other from an agricultural yard close to a freshwater reservoir. The habitat would suggest they may to be Daubenton’s bats, however we have been unable to confirm identification to species using acoustic techniques alone. We’ll explore these areas more in 2024 using the Waterways survey methodology.
Figure 1: Maps of species presence on Skye in 2023 as part of surveying for Species on the Edge
* Some of the pipistrelles were unable to be identified to species level.
** The Myotis spp. records were from passive acoustic monitoring and, as their calls are notoriously difficult to identify to species level, we’re only able to identify these bats to genus.
2.2 Monitoring in Orkney
2.2.1 Background
According to the NBN Atlas, common pipistrelles and noctules have been recorded in Orkney, however records are scarce, with the most recent referring to a sighting in 1990. We know that bat monitoring has taken place since then and records of common pipistrelles have increased in recent years. According to local sources, Nathusius pipistrelles and brown long-eared bats have both been recorded in the area.
2.2.2 Methodology
In 2023 our aim was to get staff and volunteers in the area used to using the bat detectors and the focus was on Sunset Surveys, using the methodology set out in the NBMP. The surveys were exploratory to look for bat presence on the islands and to train and engage volunteers. Six surveys were carried out across the season.
2.2.3 Findings
Figure 2: A map of bat presence in Orkney in 2023 as part of Species on the Edge monitoring. All of the records represent common pipistrelle.
Of the surveys carried out, common pipistrelle were recorded at each site, which is a positive sign. We hope to be able to report further records in future years as we survey more locations across the islands. There are a cluster of survey sites close-by the office of the project officer and the base for the volunteers, for their ease. Future seasons will combine passive acoustic methods trialled on Skye with in-person surveys, allowing an easier way to survey more of Orkney.
2.3 Monitoring in the Outer Hebrides
2.3.1 Background
Our focus for the Outer Hebrides is on common pipistrelle. In the NBN Atlas there are fewer than 30 bat records in the area. Common pipistrelle is the most recorded species, but the records are scarce. Other bats recorded include Plecotus spp. (most likely brown long-eared bat) and Nyctalus spp.
2.3.2 Methodology
Two surveys were conducted on South Uist, in the Outer Hebrides during 2023. Both were carried out by a volunteer on behalf of BCT. The NBMP Field Survey methodology was used, although the surveys took place outside of the official Field Survey timings. The locations were selected based on the available Field Survey sites in the area.
2.3.3 Findings
Figure 3: A map displaying the bat survey records from 2023 on the Outer Hebrides as part of Species on the Edge Programme, Protecting Scotland Island Wonders Project.
We are unable to draw conclusions yet about bats in the Outer Hebrides, but this is a start to better understanding of bat distribution on the islands. We have an additional, precious record of common pipistrelle.
Through the Youth Panel, we have found a willing volunteer to start a bat group, to encourage further survey uptake and to resource and engage more people with the world of bats in the Outer Hebrides. Many people do not know that bats are found on the islands.
2.4 Monitoring on the Solway Coast
2.4.1 Background
All four of our target species have previously been recorded in the area, as well noctules, Leisler’s bats (Nyctalusleisleri) and whiskered bats (Myotis mystacinus). Natterer’s bat (Myotis nattereri) and Nathusius’ pipistrelle are likely present as well, making Solway one of the most bat-diverse areas of Scotland. Brandt’s bats (Myotis brandtii) are known to occur not too far south from here and there is the exciting possibility that this species is just waiting to be discovered in this area.
2.4.2 Methodology
The Solway Project Officers have been working closely with the Dumfries and Galloway Bat Group and the Ayrshire and Arran Bat Group, to achieve our bat monitoring targets for the Solway area. Together they conducted 12 Sunset Surveys, two of which were open to the public.
Survey sites were chosen based on accessibility and favourable habitat features for each species.
2.4.3 Findings
Soprano pipistrelle has previously been recorded in the area more than any other species, which is reflected in our maps. Common pipistrelle have also been widely recorded. We are unable to identify the Myotis recordings to species level.
While Nyctalus spp are not included in our target species, they have been recorded in the area, and it is great to be able to add five noctule and one Leisler’s bat record to the NBN Atlas, which will add to our understanding of bats in the area in future years.
Figure 4: Bat records for Solway as part of Species on the Edge Protecting Scotland’s Island Wonders 2023.
3. Data flow
The data gathered has been mapped, and records submitted to the NBMP, where appropriate, and the NBN Atlas. This will ensure that the records will contribute to our wider understanding of species population trends and help us to better understand how we can support our Scottish bats.
The project will retain the biological data for the project’s own use, to better understand the bats in our focal areas and report against where we are on the Species Recovery Curve. We’ll be using these findings to develop guidance to enhance bat friendly habitats, increase the connectivity between key feeding and roosting sites, and generally support our local bat populations.
4. Plans for 2024
In the first year we undertook 59 bat surveys across the project areas, greatly increasing the available bat data, in doing so we trained 50 people in bat survey techniques (and a further 20 in sensitive habitat management for bats and other wildlife through Sharing Good Practice events). We feel certain that the officers in different project areas are becoming more confident with bat species ID and survey techniques.
In 2024 our monitoring work will continue across all four of our project areas, with a strong focus on passive acoustic techniques in Orkney and the Outer Hebrides. A variety of monitoring methods will continue to be used in the Solway area, and we will extend our monitoring efforts to cover more of the Argyll and Inner Hebrides area.
On Skye we will be working closely with crofters using passive acoustic monitoring techniques, and we will continue to build relationships with those landowners who have worked with us so far. A focus will be on using the NBMP methodology, carrying out several Roost, Field and Waterways surveys. We hope to train volunteers to take these sites on, so we can continue to get bat records both during the project and long into the future.
We’d like to say a big thank you
This work has been made possible, not only by the partners and funders involved in the programme, but also by the many volunteers, people and organisations who have contributed along the way. Without the support of our local communities and land managers, we would be unable to achieve our monitoring goals for bats in Scotland – Thank you!
To get in touch about the project or to learn more about how you can help please contact Cathryn Baillie (cbaillie@bats.org.uk)
