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Summary of findings

This report presents the findings of the National Bat Monitoring Programme (NBMP) up to 2016.

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

Data from four 'core' NBMP surveys are used to produce population trends: Roost Count, Hibernation Survey, Field Survey and Waterway Survey.

Volunteers taking part in our four core surveys contributed approximately 17,700 hours of their time, representing an in-kind contribution to the NBMP of £264,760.

In total 6,330 sites have been surveyed as part of the NBMP since its inception in 1996. In 2016 1,984 sites were surveyed by 960 volunteers.

At present sufficient data are collected by the NBMP to produce population trends for 11 of Great Britain's 17 resident bat species.

Of these species, all are considered to have been stable or to have increased since the baseline year of monitoring (1999 for most species).

Species considered to have increased in Great Britain in comparison to the baseline year are greater horseshoe bat, lesser horseshoe bat, common pipistrelle and soprano pipistrelle. There is also evidence from the Hibernation Survey that populations of Natterer's bat have increased, however this finding should be treated with caution until the effect of this species' roost switching behaviour on the Roost Count trend is better understood.

Species considered to have been stable in Great Britain in comparison to the baseline year are noctule, serotine, Daubenton’s bat, whiskered/Brandt's bat and brown long-eared bat. However these findings should be treated with caution for several species:

Serotine is encountered relatively infrequently during surveys and therefore there is a high level of uncertainty associated with serotine trends, meaning population changes are more difficult to detect for this species.

Trends for whiskered/Brandt's bat combine data from two species with differing ecological requirements and potentially differing conservation status, and may also include records of a third cryptic species, Alcathoe bat.

For brown long-eared bat, the Roost Count trend shows no significant change since the baseline year, while the Hibernation Survey shows a marginally significant decline in the most recent year when compared to the baseline year. Given the provisional nature of estimates for the most recent year, the small margin of significance in the Hibernation Survey trend and the fact that this margin is likely to change when additional years of monitoring data are added to the trend, there is not yet sufficient certainty to assess the population as declining, however this will need to be carefully monitored and the assessment potentially revised in light of the results from the next year of monitoring.

No species for which we produce population trends is considered to have declined significantly since the baseline year.

While data from the National Bat Monitoring Programme indicates that populations of the bat species we monitor are stable or recovering, it should be remembered that these trends reflect relatively recent changes in bat populations (since 1999 for most species). It is generally considered that prior to this there were significant historical declines in bat populations dating back to at least the start of the 20th century. This suggests that current legislation and conservation action to protect and conserve bats is being successful, and it is vitally important that this continues.

 

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