C8. Mammals of the wider countryside (bats)

 

Type: State Indicator

 

Indicator Description

Bat species make up a third of the UK’s mammal fauna and occur in most lowland habitats across the UK.  The indicator shows changes in the population size of eight widespread bat species, based on summer field surveys and roost counts and winter hibernation counts.  Population change between 1999 and 2016 is analysed using a statistical model developed by the Bat Conservation Trust. 

Summary

 

Between 1999, when trends from standardised large-scale monitoring became available through the National Bat Monitoring Programme (NBMP), and 2015, bat populations have increased by 34%.  An assessment of the underlying smoothed trend shows this is a statistically significant increase. 

In the short term, between 2010 and 2015, an assessment of the underlying smoothed trend shows that bat populations have shown no significant change in population size.

 

Figure C8i.  Trends in bat populations, 1999 to 2016.

Figure C8i. Trends in bat populations, 1999 to 2016.

Notes:

 

  1. The headline measure is a composite index of eight bat species: brown long-eared bat, common pipistrelle, Daubenton's bat, lesser horseshoe bat, Natterer’s bat, noctule, serotine and soprano pipistrelle.
  2. The model used to produce the indicator has changed since the previous publication, and these results are therefore not directly comparable (see Background section for more details). 
  3. The line graph shows the unsmoothed trend (dashed line) and smoothed trend (solid line) with its 95% confidence interval (shaded).
  4. The bar chart shows the percentage of species which, over the time periods of the long-term and short-term assessments, have shown a statistically significant increase or decline, or no significant change.

Source: Bat Conservation Trust.

Five species have increased over the period of the long-term assessment: common pipistrelle, Daubenton’s bat, lesser horseshoe bat, Natterer’s bat, and soprano pipistrelle. 

Three species have shown no significant long term change in population size: brown long-eared bat, noctule and serotine.  In the short term, between 2010 and 2015, three species continue to show an increase: common pipistrelle, Daubenton’s bat and lesser horseshoe bat.  Five species, brown long-eared bat, Natterer’s bat, noctule, serotine and soprano pipistrelle, have shown no significant short term change.  No species show a decline in either the long- or short-term.

Long and short term assessments are run to the penultimate year of the trend as the most recent smoothed data point (2016) is likely to change as future years of data are added.  The assessment of change in the latest year (2016) is based on unsmoothed data. There was a small dip in the unsmoothed index between 2015 and 2016 but this result is not significant and should be treated as provisional for the reason outlined above. 

Assessment of change in widespread bat populations

 

Long term

Short term

Latest year

Bat populations

2010 indicator improving
1999–2015

2010 indicator stable
2010–2015

Decreased (2016)

Note: Long-term and short-term assessments are made on the basis of smoothed trends to the penultimate year (2015) by the Bat Conservation Trust.  This is because the most recent smoothed data point (2016) is likely to change in next year’s update when additional data are included for 2017. The latest year assessment is based on unsmoothed data.  It is provided for transparency, but the decrease is not statistically significant. 

 

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Download Evidence statement

 

Last updated: August 2017

Latest data available: 2016 (2015 smoothed)