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Lesser horseshoe bat population trends

The results of the UK population trend analysis for lesser horseshoe bat from the Hibernation Survey and the Roost Counts are shown on this page, and interpretation of survey results.

Population trends are also calculated for lesser horseshoe bats in England and Wales.


Hibernation Survey

UK index of lesser horseshoe bat population from Hibernation Surveys

Lesser horseshoe bat Hibernation Survey UK 2013

Note: The trend for 2013 is shown as a dashed line to indicate that it is provisional. The figure shows trend analysis results (solid line) with 95% confidence limits (dotted lines).

Trends are adjusted to allow for the effect of temperature (as measured by observers) and the month of survey. The 2013 index has recovered from the low counts in 2012 and overall the index is currently 109% above the 1999 base year value, equivalent to an annual increase of 5.4%. The upward trend is significant.

From all years for which data are available (1990-2013), counts from a total of 227 sites contribute to the overall trend analysis. Of the 437 hibernation sites with valid data from 2013, 141 (32.3%) had lesser horseshoe bats present.


Roost Counts

UK index of lesser horseshoe bat population from Roost Counts

Lesser horseshoe bat Roost Count UK 2013

Note: The trend for 2013 is shown as a dashed line to indicate that it is provisional. The figure shows trend analysis results (solid line) with 95% confidence limits (dotted lines).

The index is currently 60.7% above the 1999 base year value, equivalent to an annual increase of 3.5%. The upward trend is significant although the increase has levelled off since 2011.

Data from 256 sites surveyed between 1997 and 2013 contribute to the overall trend analysis. In 2013, 171 roosts had valid data and 169 of those had bats present.


Interpretation of survey results

The significant upward trend from both surveys indicates that the population has increased since the start of the monitoring programme. The increase in lesser horseshoe bats is likely to have resulted from a succession of mild winters over this period enhancing winter survival, and direct positive conservation action. The increase is seen in both England and Wales with no significant difference in the trend between countries.

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Click here for details on how the population trends are calculated.

 

 

 

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