Devon Wildlife Trust
Since the grant was awarded we have been busy using our SM4 detectors and the new microphones. They have been out as part of two citizen science winter research surveys – why leave the detectors idle all winter?! – looking at landscape usage by greater horseshoe bats in the colder months. We are just starting to analyze the results and have picked up lots of recordings. Unfortunately we have lost some as the batteries are losing voltage in the really cold weather – but we hope to be able to report on the findings over coming months.
The project team are just gearing up to the start of our main citizen science programme – the Devon Bat Survey! The idea behind this is that anyone can take part by borrowing a bat detector from one of our 20 monitoring centres and surveying a chosen 1km grid square. Bookings opened two weeks ago and over a third of the 991 slots are already booked for this summer! The detectors and all the kit are in the process of being taken out to the monitoring centres, ready for the first sessions to start on March 29th. We are looking forward to getting the first sound files back for analysis and seeing if we can add to our knowledge of where Devon's bats are!
With only five weeks to go until the end of the 2018 Devon Bat Survey, we have received 622 SD cards back from participants, processed 650,000 sound files to look for bats and sent out 528 reports! We have two dedicated volunteers who are helping with the survey, one of which has already verified 1,327 greater horseshoe bat passes. We have uncovered new hotspots of activity in the county and will use these to focus our research work in 2019. We aim to have updated hotspot maps for greater horseshoes on our website by the end of 2018.
Our winter research surveys revealed some interesting behaviour. Greater horseshoes were recorded 1.15km away from their known hibernation roost, and the average temperature on the night with the highest activity (31 passes) was just 30C. This has led to more questions and we hope to be able to extend the survey this winter via a passive surveillance method of selecting twenty sites around the roost and leaving the detectors in situ for three months. Results of this will be available by mid-2019.
We're now two months into the 2018 Devon Bat Survey and 658 people have requested a square to survey – an amazing two-thirds of available booking slots! The project team has been busy supporting the 20 Monitoring Centres (see map with this report), dealing with any queries from surveyors and processing the returned data cards. A volunteer assists in downloading the data and returning the SD cards to the centres to ensure the smooth running of the survey. Tweaks and updates to last year's survey have helped to improve the efficiency and running of the survey.
Feedback from surveyors is very positive overall – they find that the instructions are clear and the equipment is easy to use. We have started to send out reports to those who have taken part – most people are amazed at the variety of bat species using the countryside near their homes – up to 10 or 12 species in some cases. Data from the winter surveys will be collated and analyzed; this all takes time as records needs verifying. Overall, this is a popular project that people all across the county are keen to get involved in.
The Devon Bat Survey’s 2018 season ended on November 2nd, with 728 people having taken part and returned sound recordings. This generated just shy of a million sound files! The team are still in the process of verifying the number of bat passes, but initial analysis shows that there is likely to be in excess of 500,000 confirmed passes. This year we recorded 3,376 greater horseshoe passes at 270 locations – a much higher figure than in 2017. This included two new hotspots that the project was previously unaware of, and these will be investigated further in 2019 with targeted surveys. Results from 2018 can now be found on our website.
All the data for non-horseshoe bat species is currently being manually checked by our project volunteers to confirm the species identification assigned by our automated classifier. Volunteers have also received training on sonogram analysis, starting with AnalookW software and progressing to Kaleidoscope. Once checked the records are sent to the Devon Biodiversity Records Centre where they are available for use to inform conservation priorities in the county. The greater horseshoe records are already contributing to a new Supplementary Planning Document for one area of Devon, providing additional protection to populations at risk from housing developments.
All greater horseshoe records are helping the project to focus its land management advisory work. It allows us to link up areas of known greater horseshoe use, providing the bats with additional routes through the countryside, potentially opening up new feeding grounds to them. It is also opening up investigatory routes to look for new roosts. Some of the records from 2018 will now be cross- referenced to the database of existing roost location records. Where no roosts are currently known in the locality, we will focus recording efforts in 2019 and 2020 to try to establish where these bats are living.
The winter 2017/18 detector survey provoked some interesting questions about landscape usage during what is normally assumed to be a hibernation period for greater horseshoe bats (Braunton report attached). Because of this, a second winter survey has been set up to attempt to answer further questions in 2018/19. Twenty SM4 detectors have recently been placed in static locations within the countryside around a known hibernation roost (including a detector at the roost exit). The detectors will record for at least three months during the main winter period, and all activity will be compared to weather data and habitat type. Any significant findings will help to tailor our land management advice around hibernation roosts and will be disseminated to project partners and the wider public.