The National Bat Monitoring Programme (NBMP) Annual Report 2017 has been published. Organised by the Bat Conservation Trust (BCT) in partnership with the Joint Nature Conservation Committee (JNCC), the NBMP co-ordinates and collates the results of annual bat surveys undertaken by thousands of volunteers.
The data is used to monitor change in the population trends of eleven of Great Britain’s seventeen resident bat species – trends are not produced for Bechstein’s, Alcathoe, Nathusius’ pipistrelle, Leisler’s, grey long-eared, greater mouse-eared or barbastelle. Trends are provided at GB-level, in addition to UK and country-level where sufficient data is available – eleven species in England, four species in Scotland, seven species in Wales, one species in Northern Ireland and one species at UK level. Four core surveys produce the data: roost count, hibernation survey, field survey and waterway survey – this means that bats are surveyed at more than one stage of their annual life cycle for some species.
A total of 6,766 sites have been surveyed since the NBMP began in 1996; the 2017 survey saw 1,867 sites surveyed by 929 volunteers, contributing approximately 16,634 hours, which represented an in-kind contribution of £247,123.
In order to identify problems for bat populations at an early stage, the NBMP uses an ‘alert’ system for individual species population trends:
- Red alert: severe decline of 50% or more over twenty-five years (equivalent to a 2.73% decline per year).
- Amber alert: moderate decline of between 25–49% over twenty-five years (equivalent to a 1.14% decline per year).
The sample sizes collated by the scheme are considered sufficient to detect an Amber or Red Alert change within twenty-five years, at most.
The results of the surveys for the eleven species of bat, where sufficient data allows trends to be produced, indicate that all species are stable or have increased in numbers since the baseline year of monitoring –1999 in the majority of cases. Three species appear to have increased in Great Britain, these comprise greater horseshoe, lesser horseshoe and common pipistrelle. The report also advises that whilst Natterer’s bat populations appear to have increased when compared to the baseline, the results should be treated with a degree of caution until ‘roost switching behaviour’ of this species is better understood. A number of species’ populations are considered to be stable when compared with the baseline year: Daubenton’s, whiskered/Brandt’s, soprano pipistrelle, noctule, serotine and brown long-eared. The results for serotine and whiskered/Brandt’s are also treated with a degree of caution by the report due to frequency of encounters during surveys and combined data issues, respectively.
The overall positive news is that none of the population trends for the species analysed have declined significantly, suggesting that legislation and conservation action to protect bats is proving successful. The importance of maintaining this protection and building on current measures is reinforced by the NBMP results.
The next report is due to be published in May 2019 and will detail the results of surveys undertaken up to and including the summer of 2018.
Bat Conservation Trust, 2018. The National Bat Monitoring Programme. Annual Report 2017. Bat Conservation Trust, London. Available at http://www.bats.org.uk/pages/nbmp_annual_report.html
Header Image: Soprano pipistrelle (Pipistrellus pygmaeus). Credit: Evgeniy Yakhontov / Wikimedia Commons.