Department for Environment, Food and Rural Affairs

Countryside Research Programme: Research Findings

The UK's National Bat Monitoring Programme
Final report 2001

Executive summary

The full report is available on the Bat Conservation Trust website at:
www.bats.org.uk

Introduction

  1. Effective bat conservation relies on gathering information to identify changes in populations that are of conservation concern. In the UK, a paucity of quantitative historical data means that population trends of the 16 species of bats are, in general, poorly known.

  2. In December 1995, the Department of the Environment, Transport and Regions commissioned a five-year programme of research (1996-2000), the National Bat Monitoring Programme, with the overall goal of developing an effective monitoring strategy for resident species of bat in the UK.

  3. This programme is designed to address obligations to conserve bats under European directives and international agreements, in particular the Agreement on the Conservation of Bats in Europe (Bonn Convention) and the EU Habitats and Species Directive. It is expected to provide relevant information about bat numbers which can then be compared with targets outlined in National Biodiverisity Action Plans and to provide data of value to broader conservation actions, and to policy development and implementation.

  4. The programme relies on data gathered by volunteers across large numbers of sites. Identifying trends in such data with confidence is not a simple task, although well planned survey design have reduced analytical difficulties. One of the most important features of any monitoring programme is to differentiate between natural fluctuations in population size and changes that are caused by anthropogenic factors. The NBMP has adopted sampling strategies to minimise bias and observation error, and maximise precision and hence the probability of detecting significant population changes as early in the monitoring process as possible. Power analyses have been employed to guide survey designs that will make reliable inferences about population trends.

  5. Although there are obvious difficulties in monitoring bats, it is essential to improve techniques and establish a sustainable monitoring program that will contribute to conservation and policy interests.

Target species, methods and sampling

  1. Three principal methods have been applied: observations at summer maternity roost sites, and at winter hibernation sites, together with summer field surveys using bat detectors. Target species in the programme are Rhinolophus ferrumequinum, R. hipposideros, Eptesicus serotinus, Nyctalus noctula, Myotis daubentonii, M. nattereri, Pipistrellus pipistrellus and P. pygmaeus.

  2. Standardised monitoring protocols have been developed to collect UK-wide baseline data for each of the target species. To cross-validate, a double-sampling approach has been applied whereby each species is monitored by two of these methods.

  3. Where appropriate, sites are sampled in an optimum random-stratified design to maximise the precision of national population estimates. The ITE land classification system is the base stratification system.

Progress and recommendations

  1. The NBMP has demonstrated that trends in bat populations can be statistically identified from data collected through its monitoring schemes. The UK lesser horseshoe bat population has risen by approximately 4.8% per year (between 2.6% to 6.9%) over seven years (1993 to 1999). This upward trend is mainly due to an 11% per year rise (between 5.3% and 17.8%) over the previous three years (1997-1999). Differences exist between the English and Welsh populations, an overall decline of around -3.2% per year (between -8.1% and +2.0%) is evident in the English population, in contrast to a 6.2% per year rise (between 3.8% and 8.5%) in the Welsh population from 1993 to 1999. A longer run of data is needed to establish whether these trends will be sustained.

  2. A range of pilot studies have been conducted, leading to the implementation of six key annual national monitoring schemes for eight target species of bat. Key schemes, length of time they have been run and number of sites included in the network are:

Maternity colony monitoring

Field survey monitoring

Hibernation site monitoring

  1. Pilot studies highlighted problems in the use of a maternity colony monitoring scheme for Natterer's bats, and the need for an increased number of sites. Standardisation of greater horseshoe maternity colony counts has not been possible, but counts are currently being collated. Analyses of data from other schemes have not identified any major problems with current protocols, although some minor changes are recommended.

  2. Improved summer and winter distribution maps have been produced for all UK bat species, and published in a provisional UK Bat Atlas. Records for the maps were collated from a wide range of sources, and included resultantrecords from NBMP monitoring schemes.

  3. To date over 1,500 people have been recruited to the programme, and of these 851 volunteers have participated in monitoring schemes and contributed data. The volunteer recruitment rate has risen consistently from year-to-year and is still rising. Over 60 training workshops have been delivered. New and renewed recruitment and training initiatives are recommended.

  4. A dedicated relational database has been built (Access 97) to store NBMP data. The database model and management systems have been reviewed and structural changes recommended to improve efficiency and ease of data transfer to Recorder2000 and the Countryside Information System (CIS).

  5. Analyses to demonstrate the potential of integrating bat monitoring data with other strategic land use monitoring data is currently underway in collaboration with the Environment Agency.

  6. Key methodological recommendations are to maintain annual monitoring of target species by a volunteer network and to ensure a minimum of 30-40 sites per monitoring scheme are consistently surveyed each year. Monitoring schemes for two further species (brown long-eared and Leisler's bat) should be integrated into the programme over the next two years. Research studies to develop novel methods, in particular for woodland species, should be initiated over the next five years.

  7. There is no doubt that full and effective implementation of a monitoring programme for bats requires considerable improvements in our knowledge and understanding of bat populations. Accordingly, there is a need for a significant increase in research at the genetic, species and ecosystem levels. Surveillance schemes are in operation now. However, it is essential that schemes are supported by research and validation projects so that they can be assessed and improved.

Published 20 February 2002/Updated 15 April 2002
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