Bat breeding area given Local Wildlife Site status thanks to Yorkshire Water’s Batman

The project began when Sean Davey, lead ecologist at Yorkshire Water, found bat droppings at the entrance to an abandoned mine on a moorland above a Yorkshire Water  reservoirs. The research that followed discovered other mine shafts nearby, and soon confirmed that this was an ‘autumn swarming’ site for several species of bat - where they go every year to mate in the autumn. Because of its important role in breeding, swarming is crucial for maintaining healthy bat populations in the wild.

An intensive year of surveys in 2023 was led by Davey, a bat specialist and SYBG member, supported by other volunteers from the local bat group. The team used 24/7 acoustic monitoring and filming with night vision equipment to monitor activity and confirm the different species of bat visiting throughout the year. They also used specially licensed techniques to safely catch swarming bats, in order to identify the individual species and assess their breeding condition.

The results of the year-long study have shown the importance of the mines at Harden for four species of swarming bat. The research also found that some of the same species return in winter to hibernate in the sheltered pits. Another four kinds of bat were recorded foraging over the moorlands in summertime, taking the total recorded to eight species for the site. These findings have convinced the Barnsley LWS panel that it is an area worth protecting for the future.

Cllr Robin Franklin, Cabinet Spokesperson for Regeneration and Culture, said:  “It’s great to hear that we have protected species in our borough.  Local Wildlife Status (LWS) will help to keep their habitats safe.  Bats as a group provide an excellent indicator of the wider health of their eco-system; monitoring projects like this are therefore an important tool for conservationists.  Warming climates in coming years may see new bat species spreading north from their existing rangers further south.  Further monitoring could help to detect species not yet found in Yorkshire.”

Sean Davey, lead ecologist, Yorkshire Water, said: “Bat swarming sites are more commonly found in wooded lowland areas so it’s particularly interesting to find swarming happening up on this exposed moor with no trees around! It is currently the only known bat swarming site in Barnsley and one of few places in South Yorkshire where this activity can be studied.

“Swarming sites are thought to have quite a large ‘catchment’, with tiny bats flying impressive distances from the surrounding areas in order to swarm and find a mate. Female bats only give birth to one offspring each year, so swarming in the autumn is critical for raising the next year’s generation of bats.

“Because of its importance for breeding, we need to know where bat swarming happens so that key sites can be mapped and protected. Better information informs better conservation at a landscape scale, helping to link up important areas and improve habitat for bats. All of this can help bat populations to grow and hopefully become more resilient to the future impacts of climate change.”

In the face of the climate and wider ecological emergency, it’s more important than ever to improve our understanding of UK wildlife species and the major threats they face. Upland habitats may be especially threatened by impacts from global warming, with increased risk of moorland fires, drying out of blanket bog wetlands, and changing or extreme weather patterns, all posing risks to bats, birds and the other iconic species of this fragile environment.

The monitoring work at Harden is expected to continue; the early results are encouraging but there is much to learn about how and why bats visit this particular site, and how they use moorland habitats more widely. This upland site can host future research and, by surveying bat activity year on year, conservationists can track population trends and monitor how bats are doing in the surrounding area.

Background in more detail

The first find took place in August 2022, when ecologist Sean Davey found bat droppings at the entrance to an abandoned mine during a moorland survey above one of Yorkshire Water’s reservoirs.  The monitoring work that followed confirmed that bats were visiting late at night for what appeared to be swarming events; a search of the surrounding land also found another four abandoned mine shafts located nearby.

Working with local experts at the South Yorkshire Bat Group (SYBG) and others, bat-friendly access points were designed to improve safety covers on several mine entrances to allow the bats to go about their nocturnal business more freely. With the support of the YW Land & Property team and a specialist contractor the approved designs were installed in late 2022.

An intensive year of surveys in 2023 led by Davey aimed to investigate bat activity occurring on site. The research team used techniques including 24/7 acoustic monitoring and filming with night vision equipment to confirm the different species of bat visiting the site, to monitor activity and establish how bats were accessing the mine shafts including those with the newly modified entrance features. Specially licensed techniques were also deployed to safely catch swarming bats in a ‘harp trap’, in order to confirm the individual species and allow their breeding condition to be assessed.

Who was involved?

The project was led by Sean Davey, lead ecologist at Yorkshire Water, in close collaboration with the South Yorkshire Bat Group.

As an ecologist at Yorkshire Water, Sean works with colleagues in the Environmental Assessment Team and the wider business to deliver biodiversity and conservation programmes, often in close partnership with local NGOs, charities and landowners, to benefit nature across Yorkshire. The work of the EAT ranges from conservation aimed at animals such as bats, water voles and white-clawed crayfish, to fish passage and river restoration schemes, through to landscape-scale habitat restoration projects.

SYBG is a voluntary organisation committed to studying and conserving bats in the South Yorkshire region. Already contributing partners to the National Bat Monitoring Programme (a national effort coordinated by the Bat Conservation Trust), they assisted Sean throughout the year-long study providing volunteers, help with equipment and specialist expertise.

Tech support for 24/7 monitoring

The team couldn’t be onsite 24/7 but were able to deploy ultrasonic bat detectors to record bat activity at four locations across the year. Detectors were left out for months to get huge samples of bat activity, with the data collected and automatically processed using computer algorithms - which can identify the different bat species from the ‘echolocation’ sounds they make in flight. The team also used a novel filming technique to capture bat swarming in action using custom-built CCTV equipment. All this technology made the long study possible, but it still involved plenty of human effort!

What have the results of the year-long survey revealed?

The Harden study recorded no less than eight bat species using this remote moorland site. The headline findings and outcomes were:

• Four bat species are swarming on the site in autumn: Natterer’s bat Myotis nattereri; Daubenton’s bat Myotis daubentonii; whiskered / Brandt’s bat Myotis mystacinus / brandtii; and, the brown long-eared bat Plecotus auritus. Bats use the sheltered and undisturbed mine shafts for winter hibernation too.
• Bats quickly adapted to use the improved bat entrances to access the mine shafts, and were confirmed swarming at all four mine areas in 2023.
• Pipistrelle and Noctule bats also feed over the heather moorlands in the summer months. The flowering shrubs attract an abundance of moths, midges, craneflies and other insects that bats love to eat.
• Long-term monitoring has revealed how each bat species uses the moorland differently, and how much the activity levels can vary from month to month.
• The research has demonstrated the importance that mines and other relics of human industry can have as breeding and sheltering areas for bats, particularly in a region with few natural caves. To help these mammals recover from historic population declines it’s crucial that key sites receive legal protection and are not lost.
• The LWS designation puts this new bat site on the nature map. It will help guide local conservation policy, informing development of the Local Nature Recovery Strategy due for publication in April 2025.

The research project has shown that four bat species – possibly more - are migrating up to this exposed moorland to engage in a secretive social event called ‘autumn swarming’. Bat swarming usually happens at caves, mines and other underground places; its where some species go to pair up with a mate, flying from far away to reach these important social hubs – so swarming sites can be crucial for the health of bat populations across a much wider landscape.

How will the results be used?

The research has provided the evidence to get the Harden site protected as Local Wildlife Site (LWS).  This puts this bat site on the nature map, and gives a level of protection which needs to be taken into consideration for any future development or planning proposals in the local area.  The research will also be used to guide future management of the site by Yorkshire Water to benefit bats.

The monitoring work at Harden will continue: the early results have been encouraging but there is much to understand about how and why bats come to this particular site, and how they use moorland habitats more widely. This upland site can host future research and, by surveying it year on year, it can help conservationists to track long-term population trends and monitor how bats are doing in the surrounding area.

Bats as a group provide an excellent indicator of the wider health of their ecosystem, so monitoring projects like this can be a valuable tool for conservationists. Warming climates in coming years may in fact see new bat species spreading north from their existing ranges further south – so monitoring could help to detect species not yet known to be in Yorkshire.

Ongoing projects by the SYBG will continue the search for new sites where bats may be swarming and hibernating. Given the extensive legacy of mining in South Yorkshire the group believes it is likely that more undiscovered swarming sites are still to be found. Such sites are likely to be under threat, and many former mines will have already been backfilled or blasted in when mining stopped. However, if structures are home to bats then they receive strict legal protection and should not be disturbed. Engineering solutions can make dangerous mine shafts safe for people whilst respecting the needs of our nocturnal neighbours.

In the face of climate change, it’s more important than ever to improve our understanding of ecology and the threats to UK wildlife so that we can take the right action to protect habitats and slow or reverse population declines. Upland habitats may be especially under threat from global warming, with increased risk of moorland fires, drying out of blanket bog wetlands, and changing or extreme weather patterns all posing risks to bats, birds and the other iconic species of this fragile environment.

Further bat background:

https://www.bats.org.uk/our-work/national-bat-monitoring-programme

https://www.bats.org.uk/our-work/science-research/passive-acoustic-surveys/nightwatch

https://www.bats.org.uk/our-work/science-research/passive-acoustic-surveys/british-bat-survey

https://www.bats.org.uk/

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