NBMP Annual Report: Bats continue returning to the night skies

While several bat species remain at risk of extinction there is some good news announced today for some - but not all - of Britain’s bat species. The latest scientific findings show encouraging continuing signs of slow recovery for several of the species being monitored by a long-standing citizen science project run by the Bat Conservation Trust and funded by JNCC.

Scientists say there is still a long way to go, but the results suggest existing protective laws and conservation actions over recent decades to help bat populations are paying off.

The results are from the National Bat Monitoring Programme (NBMP) up to summer 2022 and reflect relatively recent changes in bat populations, since 1999 for most species. We are only able to produce these results thanks to all the volunteer citizen scientists who have been collecting data for over two decades.

Among the most heartening is a continuing rise in two of Britain’s rarest bats, the greater horseshoe and lesser horseshoe, which in previous centuries disappeared from many areas of their former ranges.

Long term monitoring over the period since 1999-2022 indicates that greater horseshoe bat hibernation roost counts increased in Britain by 233% and lesser horseshoes by 187% since 1999.

There is also an encouraging rise in counts for Natterer's bat, common pipistrelle and soprano pipistrelle. Daubenton’s bat, noctule, brown long-eared bat, serotine and whiskered/Brandt’s bats are regarded as stable overall across Britain, when compared with the baseline year of 1999.

A MIXED PICTURE

However, a closer look shows there is regional variation in bat population trends across England, Wales and Scotland.

• Daubenton’s bat shows a significant increase from the Hibernation Survey for England, but no significant change for GB or Wales
• Daubenton’s bat shows a significant increase from the Waterway Survey for Wales, but no significant change for UK, GB, England or Scotland
• Common pipistrelle shows a significant increase from the Field Survey for GB and England, but no significant change for Scotland
• Soprano pipistrelle shows a significant increase from the Field Survey for GB and Scotland, but no significant change for England
• Brown long-eared bat shows a borderline significant decrease from the Hibernation Survey for England, but no significant change for GB and Wales

The brown long-eared bat trend for England referred to above has been going down in the last few years so this is something we will need to monitor closely over the coming years to see if it becomes a sustained trend. The brown long-eared bat is nicknamed a ‘whispering bat’ because its calls are so quiet. They roost in lofts and are difficult to detect due to being light shy as well as quiet. They are particularly vulnerable to light pollution which has increased in recent years, and also loft and barn conversions since they like to roost in roof voids. Like many other species they are dependent on protection from strong planning policy and strongly enforced wildlife laws.

All 11 species being monitored are considered stable or to have increased overall, despite regional variations, since the baseline year of monitoring (1999 for most species). However, we do not yet have trends for some of the species which are habitat specialists, particularly woodland specialists which can be difficult to monitor. These species are particularly vulnerable to habitat loss.

Kit Stoner, Chief Executive of the Bat Conservation Trust which leads the NBMP, said:

“While the bat species we monitor are all stable or recovering, it should be remembered that these trends reflect relatively recent changes in bat populations. There were significant historical declines in bat populations throughout the 1900s. However, this positive news suggests current legislation and conservation actions to protect and conserve bats are working and bringing success, and it is vitally important that this continues.

“Britain’s bat species are not out of the woods yet - some are still too rare or elusive to monitor reliably and it’s only thanks to so many wonderful, dedicated volunteers that we now have a clearer picture of where we are achieving better bat conservation and where efforts need to increase. Some recorded bats are too sparse or challenging to monitor to show trends, including Bechstein’s bat, grey long-eared, barbastelle, Nathusius’ pipistrelle, and Alcathoe’s bat. We only know of two individual greater mouse-eared bats in Britain, although this doubles last year’s count of one single bat!”

One third of Britain’s most highly threatened mammal species are bats. Among these, the International Union for the Conservation of Nature (IUCN) national status for the greater mouse-eared bat is critically endangered; the grey long-eared bat is endangered; the barbastelle and the serotine are vulnerable. Nathusius’ pipistrelle and Leisler’s bat and are classed as near threatened.

Bats are the top nocturnal predators of flying insects in Britain. They are long-lived and most only have one pup per year, making them slow to recover from population declines which is why their legal protection is so important.

The historical declines have been blamed on more intensive farming methods, along with loss of roosting and foraging habitats, persecution, the use of pesticides, poor water quality, declines in insects, irresponsible development and land-use change.

Bats remain vulnerable to pressures such as landscape change, unsympathetic development and emerging threats such as new building practices, climate change, wind turbines, light pollution and any potential detrimental changes to regulations, policies and wildlife laws.

The NBMP results are thanks to 946 volunteers monitoring 1,502 sites in 2022 and contributing more than 13,000 hours of time. Across the four core survey methods plus a woodland survey more than 7,000 sites have been surveyed since 1996.

Four survey methods are used to produce NBMP long-term population trends. Roost counts involve counting bats emerging from summer roosts; hibernation surveys involve counting bats present in winter roosts; field and waterway surveys involve counting certain bat species along defined walks.

Country-level population trends are produced for nine individual species and one species group in England (11 species in total), five species in Scotland, seven individual species and one species group in Wales (9 species in total), and one species in Northern Ireland. A UK trend is produced for one species.

Through the National Bat Monitoring Programme, BCT runs a range of different surveys for people of all levels of skill and experience, including complete beginners. Details can be found at Details can be found at https://www.bats.org.uk/our-wo...

A link to the full NBMP Annual Report can be found at https://www.bats.org.uk/our-work/national-bat-monitoring-programme/reports/nbmp-annual-report

The NBMP is run by BCT, in partnership with JNCC, and supported and steered by Natural England, Natural Resources Wales, Northern Ireland Environment Agency, and Scottish Natural Heritage. We are extremely grateful to all the dedicated volunteers who have taken part in the NBMP since its inception and without whom we would not be able to monitor how bats are faring across the UK.

The NBMP is a world-leading citizen science programme which produces population trends for British bat species. This information is used by Government and conservation bodies to inform evidence needs, address policy questions and provide metrics of bat population status, change and distribution.

NBMP results are also used to measure Government progress on halting biodiversity loss. Bats are valuable indicators of ecosystem health because they rely on insect prey, a range of habitats, a healthy climate and good site management.

Effective conservation requires monitoring of underlying population trends in order to detect population declines; to ensure scarce conservation resources are targeted appropriately towards sustaining bat populations and the habitats on which they depend; and to inform policy.

We do not have data for all of Britain’s bat species as some are much harder to record reliably in sufficient numbers to yield reliable estimates. This includes habitat specialist species that are likely to be particularly vulnerable to changes in their environment.

For some species where a field survey is showing a stable or increasing trend the corresponding roost counts show declines. We believe bat roost switching behaviour skews the roost counts for some species, e.g., common and soprano pipistrelle, Natterer’s and serotine, therefore field surveys for these species are considered more reliable and we are investigating ways to address this sampling difficulty.