Population trends for bat species in the UK

This page hosts the Official Statistics ‘Population trends for bat species in the UK’ published on 29 May 2025, including data up to 2024.

Official Statistics description

Bat population trends are published as Official Statistics annually. The Statistics comprise trends of UK bat species based on data gathered through the UK-wide bat monitoring scheme, the National Bat Monitoring Programme (NBMP).

The point of first release for the bat population trends Official Statistics is JNCC’s website. The Statistics are also incorporated into the NBMP Annual Report where they are presented alongside detailed species accounts, and a broader range of bat trends for species and surveys that currently do not meet the qualifying criteria for Official Statistics.

The NBMP is a UK-wide monitoring scheme (running since 1996) consisting of four long-term structured core surveys: Field Survey, Waterway Survey, Roost Count and Hibernation Survey. The Field and Waterway Surveys involve counting specific bat species along defined transects. The Roost Count involves counting bats emerging from summer roosts and the Hibernation Survey involves counting bats present at hibernacula. All surveys are carried out during specified time periods and weather conditions.

The NBMP is run by the Bat Conservation Trust in partnership with the Joint Nature Conservation Committee, and supported and steered by Natural England, Natural Resources Wales, NatureScot and Northern Ireland Environment Agency. The NBMP is indebted to all volunteers who contribute data to the programme. Bat Conservation Ireland contributes Northern Ireland bat records collated by the Irish Bat Monitoring Programme (funded by the National Parks and Wildlife Service of the Department of Arts, Heritage and the Gaeltacht, Republic of Ireland and Northern Ireland Environment Agency).

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Scope of the statistics

• Bat population trends are presented at UK, GB and country level for those species where adequate, robust data are available from at least one of the four core surveys up to and including the 2024 field season.
• Trends presented at a GB level cover 11 of the UK’s 17 breeding bat species (nine individual species and one group of two species). For five of these, trends are presented from two separate surveys.
• Trends are presented at a country level for nine individual species and one species group in England (11 species in total), five individual species and one species group in Wales (seven species in total), two species in Scotland and one species in Northern Ireland. As trends for some species are presented from two surveys, a total of 25 separate trends are presented.
• UK level population trends are presented for five species.
• Long-term trends are presented from 1999 to 2023 (Brown long-eared bat roost count only from 2001 and Daubenton’s bat in Northern Ireland only from 2006)
• Short-term trends are presented from 2018 to 2023.

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Summary of results

In total, 7,328 sites have been surveyed across all NBMP core surveys (Field Survey, Waterway Survey, Roost Count and Hibernation Survey) since the start of national bat monitoring in 1997. In 2024, 741 NBMP volunteers completed surveys at 1,631 core survey sites.

Bat species for which trends have been published as Official Statistics are listed in Table 1, and the long-term and short-term trends for bat species at GB, UK and country scales are presented in tables 2 to 7. Note that the geographic range of serotine and both species of horseshoe bat is restricted to England and Wales only, and noctule is not found in Northern Ireland.

Following the suspension of the Hibernation Survey in 2020/21 due to Covid-19, and the lower coverage in subsequent years there is a continued impact on the ability to produce trends based on hibernation surveys in Scotland.

Table 1. Bat species for which a population trend was produced at GB, UK and country scale.

Geographic area	Number of species	Bat species
GB	11	Greater horseshoe, lesser horseshoe, Daubenton’s bat, whiskered/Brandt’s bat, Natterer’s bat, common pipistrelle, soprano pipistrelle, serotine, noctule, brown long-eared bat
England	11	Greater horseshoe, lesser horseshoe, Daubenton’s bat, whiskered/Brandt’s bat, Natterer’s bat, common pipistrelle, soprano pipistrelle, serotine, noctule, brown long-eared bat
Wales	7	Greater horseshoe, lesser horseshoe, Daubenton’s bat, whiskered/Brandt’s bat, Natterer’s bat, brown long-eared bat
Scotland	2	Daubenton’s bat, soprano pipistrelle
Northern Ireland	1	Daubenton’s bat
UK	5	Greater horseshoe, lesser horseshoe, Daubenton’s bat, serotine, noctule

 

For GB populations (Table 2), the long-term trends of five bat species (greater horseshoe bat, lesser horseshoe bat, Natterer’s bat, common pipistrelle and soprano pipistrelle) are considered to have increased; six species (Daubenton’s bat, whiskered/Brandt’s bat, serotine, noctule and brown long-eared bat) are considered stable; and no species are considered to have declined since the baseline year of monitoring (1999 for most of the surveys). There is an increasing UK trend (Table 7) for two out of the five species while the trend for three species is stable.

Short term 5-year GB trends (Table 2) for a number of species are showing a different trajectory. While the long-term trends for all seven surveys for greater horseshoe bat, lesser horseshoe bat, Natterer’s bat, common pipistrelle and soprano pipistrelle show significant increases, the only increasing short-term trends come from hibernation surveys of greater and lesser horseshoe bats, with the other trends indicating no change.

Country trends (Tables 3 to 6) illustrate regional differences in bat trends. Comparison of the long-term and short-term trends from the 25 combinations of species and survey type we have data for at country level reveals that only two trends are significantly positive in both the long-term and short-term: those derived from hibernation surveys for greater and lesser horseshoe bats in Wales. In ten cases the trend is stable in both long-term and short-term, and in one instance – serotine field survey in England – the short-term trend shows a significant increase within a stable long-term trend. Notably, 12 of the country-level trends feature a downward change in the trend when comparing long-term to short-term. This is mostly where a long-term increasing trend is stable in the short-term, but three of these are showing a significantly declining shot-term trend: brown long-eared bat hibernation survey in Wales and Daubenton’s bat waterway survey in Northern Ireland are showing a significantly declining short-term trend within a stable long-term trend, while the lesser horseshoe roost count in England shows a significant long-term increase but a significant shot-term decline.

While it is possible that these short-term trends are reflections of periodic population cycles, the fact that short-term trends are showing fewer significant increases and some are indicating a decline, there is the possibility of an external pressure or pressures impacting on bat populations. Continued monitoring of trends and research are vital to provide evidence of the causes behind any changes in trends so that effective recovery measures can be actioned for this specialised group of slow-breeding mammals.

Table 2. Population trends of bat species in Great Britain in the short-term (2018–2023) and long-term (1999–2023).

Species	Survey type	Short-term trend: Average sites per year	Short- term trend (%)	Long-term trend: Average sites per year	Long- term trend  (%)
Greater horseshoe bat	Hibernation Survey Roost Count	122 25	22.2* 12.1	122 22	241* 222.5*
Lesser horseshoe bat	Hibernation Survey Roost Count	157 134	17.6* 0.4	158 147	191.6* 73.6*
Daubenton's bat	Hibernation Survey Waterway Survey	268 234	-2 0.6	265 244	22.2 4.6
Whiskered/Brandt's bat	Hibernation Survey	162	-0.3	160	25.7
Natterer's bat	Hibernation Survey	314	2.9	308	129.2*
Common pipistrelle	Field Survey	163	1.2	170	86.8*
Soprano pipistrelle	Field Survey	163	23.8	170	61.5*
Serotine	Field Survey Roost Count	124 32	26.6* 5.3	125 36	28.4 -3.5
Noctule	Field Survey	161	5	167	30.5
Brown long-eared bat	Hibernation Survey Roost Count	297 45	9.1 -10.6*	279 58	-13.8 5.1

Trend is indicated as percentage change over the specified periods.

* = statistically significant change.

 

Table 3. Population trends of bat species in England in the short-term (2018–2023) and long-term (1999–2023).

Species	Survey type	Short-term trend: Average sites per year	Short- term trend (%)	Long-term trend: Average sites per year	Long- term trend (%)
Greater horseshoe bat	Hibernation Survey	62	5.7	64	227*
Greater horseshoe bat	Roost Count	21	3.2	18	190.1*
Lesser horseshoe bat	Hibernation Survey	69	0.2	71	137.8*
Lesser horseshoe bat	Roost Count	52	-13.4*	53	72.3*
Daubenton's bat	Hibernation Survey	201	0.1	200	30.7*
Daubenton's bat	Waterway Survey	190	5.1	200	-3.1
Whiskered/Brandt's bat	Hibernation Survey	106	3.4	109	39.3
Natterer's bat	Hibernation Survey	231	6.5	228	163.2*
Common pipistrelle	Field Survey	148	1.4	147	87.6*
Soprano pipistrelle	Field Survey	148	3.2	147	20.3
Serotine	Field Survey	119	26.2*	118	26.1
Serotine	Roost Count	31	8.8	35	-3.7
Noctule	Field Survey	146	7.3	145	7.6
Brown long-eared bat	Hibernation Survey	227	5.6	218	-8.9
Brown long-eared bat	Roost Count	35	-11.7	41	-9.7

Trend is indicated as percentage change over the specified periods.

* = statistically significant change.

 

Table 4. Population trends of bat species in Wales in the short-term (2018–2023) and long-term (1999–2023)

Species	Survey type	Short-term trend: Average sites per year	Short- term trend (%)	Long-term trend: Average sites per year	Long- term trend (%)
Greater horseshoe bat	Hibernation Survey	60	231.3*	58	470*
Lesser horseshoe bat	Hibernation Survey	88	22.9*	86	214.4*
Lesser horseshoe bat	Roost Count	82	6.3	94	76.3*
Daubenton's bat	Hibernation Survey	59	11.8	55	38.4
Whiskered/Brandt's bat	Hibernation Survey	49	-16.9	45	-21.4
Natterer's bat	Hibernation Survey	73	26.1	69	125.5*
Brown long-eared bat	Hibernation Survey	60	-53.6*	51	-27.4

Trend is indicated as percentage change over the specified periods.

* = statistically significant change.

 

Table 5. Population trends of bat species in Scotland in the short-term (2018–2023) and long-term (1999–2023).

Species	Survey type	Short-term trend: Average sites per year	Short- term trend (%)	Long-term trend: Average sites per year	Long- term trend (%)
Daubenton's bat	Waterway Survey	32	-7.1	32	10.5
Soprano pipistrelle	Field Survey	11	52.9	16	221.6*

Trend is indicated as percentage change over the specified periods.

* = statistically significant change.

 

Table 6. Population trends of bat species in Northern Ireland in the short-term (2018–2023) and long-term (1999–2023).

Species	Survey type	Short-term trend: Average sites per year	Short- term trend (%)	Long-term trend: Average sites per year	Long- term trend (%)
Daubenton's bat	Waterway Survey	28	-16*	26	7.6

Trend is indicated as percentage change over the specified periods.

* = statistically significant change.

 

Table 7. Population trends of bat species in the UK in the short-term (2018–2023) and long-term (1999–2023)

Species	Survey type	Short-term trend: Average sites per year	Short- term trend (%)	Long-term trend: Average sites per year	Long- term trend  (%)
Greater horseshoe bat	Hibernation Survey	122	22.2*	122	241*
Greater horseshoe bat	Roost Count	25	12.1	22	222.5*
Lesser horseshoe bat	Hibernation Survey	157	17.6*	158	191.6*
Lesser horseshoe bat	Roost Count	134	0.4	147	73.6*
Daubenton’s bat	Waterway Survey	262	-1.8	263	4.2
Serotine	Field Survey	124	26.6*	125	28.4
Serotine	Roost Count	32	5.3	36	-3.5
Noctule	Field Survey	161	5	167	30.5

Trend is indicated as percentage change over the specified periods.

* = statistically significant change.

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Background and Methods

Bats have been monitored systematically in the UK since 1997 to assess trends in bat numbers and distribution. The annual NBMP report presents syntheses of results from the national bat monitoring as well as other species surveys and research.

Long-term population change is assessed relative to the baseline year of monitoring (1999 in most cases) in comparison to the penultimate year of monitoring (2023). The short-term trends cover the most recent five years up to and including 2023. It is customary to use the smoothed index value from the penultimate year of monitoring for trend assessments as the index value from the most recent year (2024) can change when further years of monitoring data are added.

Because of the inter-species differences in habitat preferences The NBMP is an integrated programme that uses a number of survey methods, each appropriate for different UK bat species. This approach means that most of the species monitored are surveyed at more than one stage of their annual life cycle.

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Value of citizen science partnership approach

The ‘citizen science’ approach enables wide-scale simultaneous sampling coverage; it would be unlikely that surveys at this scale could be achieved using professional ecologists. In 2024, 741 volunteers took part in systematic NBMP monitoring surveys recording bats on 1,631 long-term monitoring survey sites, with an estimated value of £242,430 (based on an estimated 14,926 volunteer hours using Heritage Lottery fund daily rates from February 2021). In addition to yielding valuable data about bat species, research indicates that engaging in an active out-of-doors conservation/monitoring project benefits the health of the volunteers taking part.

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Confidence in results, quality assurance and caveats

NBMP volunteers follow standardised, peer-reviewed methods, and the submitted data undergo a combination of automated and manual validation and verification processes. These measures ensure that results derived from these data are scientifically robust.

Bat species differ in their biology and habitat choice, and so a range of survey types are required to ensure effective monitoring of each. The four long-term structured surveys in the NBMP are designed to achieve this. Most species are monitored by more than one of these surveys.

The statistical significance of trends is assessed and significant results are clearly presented. Confidence intervals for the indices are presented in the dataset accompanying this statistical release. Only the trends considered to be robust and unbiased are presented as Official Statistics.

Several factors can influence the number of bats or levels of bat activity at the site, and hence impact on the trends. These include temperature, weather conditions and site characteristics; or the ability to detect and identify the species present, such as bat detector model used and the volunteer’s level of skill and experience. These metadata are incorporated into the trend analysis as covariates.

At present we are not able to produce population trends for some of the rarer bat species that are difficult to monitor or rarely encountered (including Bechstein’s bat, barbastelle, grey long-eared bat), as data available for them is currently insufficient to allow the calculation of population trends.

Roost counts can be an effective way of monitoring a population in situations where a high proportion of existing roosts are counted and when the species tends to be faithful to its roost site between years. This is the case for species such as greater and lesser horseshoe bats, for which the roost count produces robust trends.

Some species, such as common and soprano pipistrelle, and potentially also Natterer’s bat, switch and/or split roosts frequently, often for long periods of time. Roost count is not considered a suitable metric to estimate population trends for these species because the high instance of roost switching behaviour creates a strong negative bias rendering any trend unreliable. As a result, trends produced from roost counts of these species are not published as Official Statistics, but the population trends are drawn only from other surveys.

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Drivers of change

A recent evidence review (Browning et al. 2021) suggests that two factors have had a positive impact on bat population trends: a reduction in human disturbance (following strict legal protection), and a milder climate, in particular over winter and spring, which has been shown to benefit horseshoe bat species. The impact of climate change on other UK bat species is less clear.

Prior to 1999 (the baseline year for most of the population trends), it is generally considered that bat populations have been declining since at least the start of the 20th century – recent genetic studies suggest a much longer period of decline for some species. These declines have been attributed to agricultural intensification, loss of roosting and foraging habitat, persecution, pesticides including the use of toxic timber treatments within roosts, water quality, declines in invertebrate prey, development, land-use change and climate change; however, evidence of the drivers of population change in bats is limited.

Bats remain vulnerable to pressures such as landscape change, climate change, development and emerging threats such as new building practices, wind turbines, and light pollution.

The positive and stable trends since the 1990s coincide with the introduction of the current legislation and conservation action to protect and conserve bats. However, the changes suggested by the short-term trends give new cause for concern.

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Involvement and contacts

These statistics were produced by the NBMP partnership to the high professional standards set out in the Code of Practice for Official Statistics, with BCT having primary responsibility for producing the statistics.

Quality Assurance was carried out by BCT and JNCC, and by members of the NBMP scheme steering group representing the Statutory Nature Conservation Bodies.

The population trends are published as a JNCC Official Statistic. If you have any queries, please contact us.

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Relation to other Official and National Statistics, and broader relevance

The statistic forms part of a suite of statistics produced through partnership monitoring schemes as part of JNCC’s terrestrial evidence programme.

The trends feed into the National Statistic Compendium – UK Biodiversity Indicators  (including one of the headline indicators on mammals of the wider countryside) as part of measuring progress towards CBD targets

NBMP data contribute to UK reporting on the conservation status of species and feed into country level reporting on Priority Species and biodiversity indicators (e.g. England biodiversity indicator 4a). They also feed into conservation assessments such as State of Nature.

Data from the NBMP are used in scientific research and to inform conservation action.

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References

Bat Conservation Trust. 2001. The UK’s National Bat Monitoring Programme – Final report 2001. Bat Conservation Trust, London. DEFRA Publications, PB 5958A

Browning, E., Barlow, K., Burns, F., Hawkins, C. & Boughey, K. 2021. Drivers of European bat population change: a review reveals evidence gaps. Mammal Review 51:353-368.  

Burns, F, Mordue, S, al Fulaij, N, Boersch-Supan, PH, Boswell, J, Boyd, RJ, Bradfer-Lawrence, T, de Ornellas, P, de Palma, A, de Zylva, P, Dennis, EB, Foster, S, Gilbert, G, Halliwell, L, Hawkins, K, Haysom, KA, Holland, MM, Hughes, J, Jackson, AC, Mancini, F, Mathews, F, McQuatters-Gollop, A, Noble, DG, O’Brien, D, Pescott, OL, Purvis, A, Simkin, J, Smith, A, Stanbury, AJ, Villemot, J, Walker, KJ, Walton, P, Webb, TJ, Williams, J, Wilson, R, Gregory, RD. 2023. State of Nature 2023, the State of Nature partnership, Available at: www.stateofnature.org.uk.

Fewster, R.M., Buckland, S.T., Siriwardena, G.M., Baillie, S.R. & Wilson, J.D. 2000. Analysis of population trends for farmland birds using generalized additive models. Ecology 81: 1970-1984.

JNCC. 2019. Article 17 Habitats Directive Report 2019: Species Conservation Status Assessments 2019. https://jncc.gov.uk/our-work/article-17-habitats-directive-report-2019.

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