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Report Number 573 Radio tracking study of greater horseshoe batsat Buckfastleigh Caves Site of Special Scientific Interest, 2003 English Nature Research Reports working today for nature tomorrow English Nature Research Reports Number 573 Radio tracking study of greater horseshoe bats at Buckfastleigh Caves Site of Special Scientific Interest, 2003 Geoff Billington Greena Ecological Consultancy Project Manager : David Appleton, English Nature Devon Area Team You may reproduce as many additional copies of this report as you like, provided such copies stipulate that copyright remains with English Nature, Northminster House, Peterborough PE1 1UA ISSN 0967-876X © Copyright English Nature 2004 Acknowledgements English Nature (in particular David Appleton) for planning, funding and licensing the activities carried out under this study, for the loan of aerial photographs and for providing copies of 1:10000 and Phase I habitat maps under their Ordnance Survey licence. The contract field surveyors Geoff Billington, Jan Collins, Alison Johnston and Marie Dee Rawlinson. The volunteer helpers Gareth Jones, Martin Longley and Siobhan Murphy. In addition to the project brief Greena Ecological Consultancy input the results into MapInfo and provided English Nature with a digital map tile. The large number of roost owners for permitting access to their land and buildings for inspections. Photographs by Geoff Billington. Summary The activity patterns of greater horseshoe bats Rhinolophus ferremequinum roosting at Buckfastleigh Caves Site of Special Scientific Interest (SSSI) were investigated over ten and eight day periods in May/June and August 2003 respectively. A total of 20 bats of both sexes were radio-tagged in the two sessions. Bats regularly commuted six kilometres to foraging areas and were recorded travelling over 8 kilometres away from the roost. The total area used by the population covered at least 50 square kilometres. Bats foraged primarily around tree lined watercourses, bushy hedgerows and tree lines surrounding pasture, rough grassland or scrub and woodland edge habitats. A total of 12 foraging areas were identified during the study. The most significant foraging areas were: south of King’s Wood, Hembury Woods to Stoodley, Hockmoor to Combe, Holne and Poundsgate area. The main commuting routes used by almost all of the bats leaving the SSSI are north across Church Hill to Buckfast, then either northwest into the valleys carrying the River Mardle and Holy Brook or further north along the River Dart. Bats also commute across Church Hill via Holne Road along hedgerows. They also commute southeast along the River Dart southeast as far as Riverford, and south to Upper and Lower Dean. Two day roosts were located and 19 night roosts were identified Contents Acknowledgements Summary 1. Objectives ......................................................................................................................6 2. Background....................................................................................................................6 3. Study area.......................................................................................................................6 4. Methods..........................................................................................................................6 5. Results 9 5.1 Tracking and bat data.........................................................................................9 5.2 Foraging ...........................................................................................................10 5.2.1 Foraging areas......................................................................................10 5.2.2 Foraging area usage .............................................................................14 5.3 Flight corridors.................................................................................................15 5.4 Daytime roost sites...........................................................................................16 5.4.1 Number of roosts and roost types ........................................................16 5.4.2 Roost descriptions................................................................................17 5.5 Night roost sites...............................................................................................17 5.5.1 Number of roosts and roost types ........................................................17 5.5.2 Roost descriptions................................................................................17 6. Discussion....................................................................................................................20 6.1 Study aims and objectives................................................................................20 6.2 Foraging distances...........................................................................................20 6.3 Primary foraging habitat ..................................................................................20 6.4 Flight corridors.................................................................................................21 6.5 Roosts...............................................................................................................21 7. Recommendations........................................................................................................21 7.1 Foraging areas..................................................................................................21 7.2 Roosts...............................................................................................................21 8. References....................................................................................................................22 Appendix 1. Maps of foraging areas, flight routes and night roosts.......................................23 Appendix II. Day roost usage data..........................................................................................35 Appendix III Night roost usage data.......................................................................................36 Appendix IV Weather conditions during survey periods .......................................................38 1. Objectives To identify the principal foraging areas and flight routes used by greater horseshoe bats roosting at Buckfastleigh Caves SSSI. Secondary objectives were to identify any night and day roosts used by the bats. 2. Background This study was commissioned and funded by English Nature and carried out by Greena Ecological Consultancy from temporary bases in holiday cottages at Blackawton and Rattery. In this study the movements of relatively large groups of bats (up to 10 per session) were examined to record the distribution and behaviour of greater horseshoe bats during early May/June and August 2003. 3. Study area Buckfastleigh Caves SSSI (NGR SX742665) contains a greater horseshoe bat maternity and several hibernation roosts, situated near the town of Buckfastleigh in Devon (Figure 1). The roost supports up to 1900 individuals (English Nature data). The majority of the study area lies within the southern part of Dartmoor National Park and is characterised by hills with extensive tracts of broadleaved and mixed woodland interspersed by pockets of small field systems enclosed by hedgerows and tree lines. Minor river valleys feed the River Dart, which drains southeast through the area in a wooded valley. Livestock rearing dominates the local agricultural landscape. The extreme north and northwest of the study area extends into the upland habitats of Dartmoor. 4. Methods Greater horseshoe bats were radio tracked over a total of 18 days from 31 May-9 June and 15-22 August 2003. All bats were caught in either a harp trap or one of several mist nets (see Figure 1). The bats were fur-clipped and the transmitters glued between the shoulder blades, using SkinBond adhesive. Bats were fitted with 0.57g 173 MHz radio transmitters, manufactured by Biotrack, with a specified minimum nine-day battery life. The bats were given time to settle down before release. Captured bats were also weighed, sexed, measured and examined to ascertain breeding condition. The bats were also checked for the presence of rings. Professor Gareth Jones (Bristol University) collected tail membrane biopsy samples (3mm diameter punched holes) from 13 bats on the 15 August, for use in ongoing genetic research. Up to three fieldworkers used Australis 26K and Sika receivers with Yaggi rigid aerials to track bats. Whip omni directional antennas were used to search for bats by vehicle. Both receivers were able to automatically scan through different frequencies, this made it possible to search for a number of tagged bats. Tailor-made recording sheets were used to record data and radio sets were used for two-way communication. Accurate bearings of bat locations were taken from hand held sightings compasses. Global Positioning Systems were used to 6 increase the speed and accuracy of surveyors. Duet bat detectors were used to confirm the presence of horseshoe bats by listening for their characteristic echolocation calls. For all tagged bats the following data was recorded: observer location, bat ID number, triangulation bearings, signal strength, apparent location or route and behaviour. When bats were commuting or at their first foraging sites, they were usually observed from elevated points (see Table 1) with each surveyor based at separate locations, in contact by radio set. On several occasions