BLACKDOWN HILLS 2014 BIG BAT SURVEY

Transcription

1 BLACKDOWN HILLS 2014 BIG BAT SURVEY 1

2 Summary The fourth Blackdown Hills Big Bat Survey was run by the Somerset Environmental Records Centre (SERC) with the help and support of the Somerset Bat Group (SBG) and the Blackdown Hills Area of Outstanding Natural Beauty (Blackdown Hills AONB). It was made possible with the generous financial support of the Blackdown Hills AONB. Without these three bodies it would not have been possible. Equally, the whole survey depended on the enthusiasm and expertise of an army of volunteers giving their time to design and walk transects, stumble about in the dark and spend hours at a computer analysing the results. The main threat to this year s survey was the uncertain weather. Some of the higher parts of some transects were foggy and the volunteer surveyors returned to base to the sound of approaching thunder. It is to their credit that no-one got seriously lost and to our good fortune that the deluge only started as people found their way home. Although there was a light breeze on more exposed land from the second half of the survey ahead of the coming storm the air was calm at the start and the night was warm at 17 degrees or more. The recordings for two transects failed and in those cases the data has been taken from the written form noting what was heard on heterodyne detectors. Such data are more subjective and less robust but are included with those provisos. As before the recordings of Common Pipistrelle (Pipistrellus pipistrellus) passes greatly out-numbered all others. Barbastelles (Barbastellus barbastellus) were recorded on four transects and Lesser Horseshoe Bats (Rhinolophus hipposideros) on two. No Leisler s Bats (Nyctalus leislerii) we recorded this year and very few Noctules (Nyctalus noctula). As for previous reports we have given a brief review after the tables for each transect. Acknowledgements Special thanks to all of the volunteers who took part in the survey: Pete Banfield, Hannah Bates, Nick Bentley, James Billing, Liz Biron, David Blake, Ros Buckley, Sarah Butcher, Dominic and Anja Cakebread, Edward Chilcott, Greg Colthorpe, Alex Corby, Dave Cottle, Jeremy and Kathleen Cuff, Tim Cuff, John Daw, Martin Drake, Mark and Francesca Farrant, John and Valerie Godsmark, Kiff Hancock, Robert Harrison, Kasia (Katherine) Howell, Daryl Hughes, David Izzard, Beth Jerrett, Ania Jurkowska, Alan Keith, Paul Kennedy, Andy Knight, Monique Kors, Philip Lewenz, Gillian Lowe, Liz Mallinson, Matthew Marshall, Brian McShane, Nick Milton, Will Molyneaux, Hannah Montag, Lila Morris, Ruth Newton, Nigel Perry, Tim Pitcher, Sara Puddy, Laura Quinlan, Ed Redgrove, Michael and Eloise Robinson, Andrew Ross, Tony Serjeant, Cath Shellswell, Chris Sowden, Helen Steinhardt, Rose Teixeira, Nick Tomlinson, Helen Turner, Susanne Ubink, William and Emma Wake, Joceline Watson, Edward and Helen Wells, Richard Winn and Carol Youngson. All the land holders that allowed the survey to take place around their holding. Transects were created in 2011 and 2012 by Cath Shellswell, Lou Pickersgill,Edward Wells and Liz Biron. Sound analysis undertaken using BatSound by Edward Wells and Cath Shellswell GIS analysis undertaken using ESRI ArcGIS 9.2 by Cath Shellswell Cover photograph: Barbastelle (Barbastelle barbastellus) by Paul Kennedy Report Authors: Edward Wells, Laura Quinlan and Cath Shellswell. 2

3 1. INTRODUCTION Whilst a number of specific bat roosts within the Blackdown Hills AONB have been known for many years, the way in which bats use the landscape of this interesting and varied part of Somerset and Devon has been only sparsely studied. Flight records have been largely anecdotal. Accordingly the AONB commissioned SERC to carry out a Batscapes study using aerial photograph interpretation and the Integrated Habitats System (IHS) to map and predict areas likely to be suitable for the various British bat species. This work produced predictive maps for a number of species based on their known habitat requirements and on the distribution of known records. There are 17 species of bat known to breed in Britain and 16 of those are recorded in Somerset. A survey for the National Bat Monitoring Programme of the Bat Conservation Trust in 2010 and 2011 revealed a number of sites for the nationally rare Bechsteins Bat (Myotis bechsteinii) in and near the Blackdown Hills. Clearly the area could be of great importance for bats. It was in this context that in addition to other surveys SERC agreed in 2011 to set up the Blackdown Hills Big Bat Survey following the model of the highly successful Mendip Hills Big Bat Survey. This not only provides a significant body of data of bat activity in the form of flight records but also encourages local people to find the bats with SERC and enjoy a largely hidden element of their local wildlife at the side of experienced bat workers. The first survey in July 2011 attracted some 63 volunteers; the second survey involved 70 volunteers and the third 62. That allowed the number of routes surveyed to be increased to 16 for 2013 and 2014 including a number in East Devon. As bats are highly mobile, their presence is a good indicator of the status of habitats and they can be used to monitor changes in the condition of the wider landscape. Intensive land management can deplete the invertebrate population and bats will move elsewhere. The data acquired by the Mendip Hills Big Bat Survey has already been used to support agri-environment agreements and wider landscape management. The way that the different bat species use the environment, particularly in relation to the use of linear landscape features to commute and feed opportunistically, is still a matter of research and debate but it can only help inform that debate to have comparative data covering a number of years showing where in the landscape bats are encountered. The Blackdown Hills represent an outstanding area in which to collect such data with their un-intensive land use and varied mosaic of habitats supported through high nature value farming and forestry. The predictive maps were used to identify potentially good areas to survey but the actual routes used were also conditioned by their practicality. Public paths were an essential part of the transect route and public roads were avoided wherever possible. It was essential that the route prescribed should be safe and able to be negotiated within a reasonable time. It was equally essential that the surveying did not disturb or put at risk any landowners, their livestock or their crops. The methods used in this survey, whilst providing robust and meaningful data, also provide an opportunity for a large number of people to experience the pleasure of listening for bats in the company of more experienced bat people. Local naturalists have discovered a whole new world in their own neighbourhood, a world which only comes to life when the sun has gone down. Sixteen transects were surveyed on 18 th of July The volunteers were divided between those transects with a minimum of two people with the majority of groups consisting of 4-6 volunteers. Heterodyne bat detectors were loaned to volunteers that did not have their own. Before the survey took place Edward Wells ran a workshop on the 27 th June 2014 to help inexperienced volunteers get some idea of how to interpret what they were likely to hear on such a detector. If bats do associate the noises from detectors with their own sounds, and it is unlikely that they do, they show no sign of being affected. Groups of 4 or 5 people walking the transects represent only a very slight and transient intrusion. Much of the purpose of repeating a survey of this kind over a number of years is to try to iron out inconsistencies caused by variable factors such as weather and farming practice. In order to correct for differences caused by the time after sunset a particular area is surveyed the routes are walked in reverse on alternate years. This makes no difference to the central part but the tables show that the earliest and latest sections vary from year to year. As in 2012 the 2014 survey began at what had been Stop 6 in the two other years. Nonetheless, the presence of bats in exposed areas and the lower incidence of the big bat species (Noctule, Serotine and Leislers Bat) than in previous years make 2014 s results appear quite like those of It is reasonable to suppose that this is an effect of high temperature and little wind, but there are many other possible variables. There is no reason to assume that the big bats are in decline in the survey area. 3

4 2. METHOD The 2014 Blackdowns Big Bat Survey is a landscape survey to collect comparable data across the Area of Outstanding Natural Beauty: (a) 16 predetermined routes (figure 1) were walked simultaneously comprising a series of 6 walking sections and 6 stationary points. Each team of volunteers listened to bats using heterodyne, time expansion or frequency division bat detectors and listed what they heard in each section. (b) At the same time one person in each group undertook a continuous recording on a wave recorder (such as a Zoom or ediro, recorder) using a frequency division Batbox Duet Bat Detector. The recordings were assigned to separate tracks for each section and then analysed to count the number of bat passes in each section and, so far as possible, assign those passes to species. 2.1 Survey Sixteen transects were surveyed. All were completed and good frequency division sound data was collected from each route. Each walk consisted of six stops of 5 minutes and six walked sections lasting an average of about 10 minutes. The stops were chosen strategically where there were potentially significant landscape features and the walks were mainly along established footpaths for the comfort and safety of the volunteers. Each transect was walked in reverse to the route followed in 2011 to ascertain whether there are differences in bat activity depending on the time of evening. For clarity in comparing years, on the maps and tables of this report the numbering of stops and walks has been shown the same for both years and a note has been made for the years when the survey was walked in reverse. All landowners along each transect were asked for permission to access their land. To create each route, a walk was drafted using OS Explorer Map 115, 116 and 128. The transect was subsequently checked to measure the timings of the sections at a steady walking pace and define the different habitats at the stops. The volunteers were provided with maps of the transect they were undertaking, a risk assessment and asked to walk the route in daylight for safety prior to the survey. Further information that was provided to volunteers is available from the Somerset Environmental Record Centre. Before starting the surveys, the volunteers met for a brief health and safety talk and then travelled to the beginning of each transect. 2-6 individuals with a mixture of bat experience from beginner to very experienced were assigned to each group. One person in each group recorded the route continuously using a Batbox Duet and a wave recorder. The surveys started at 21:30 and finished at approximately 23:30. A chosen volunteer in each group travelled to the Village Hall at Bishopswood to hand-in the recordings and survey forms. 2.2 Sound Analysis The number of bat passes made by each species or group was counted to provide a measure of bat activity along each walk section and stop section. A bat pass is a continuous stream of echolocation calls indicating a bat flying past. The number of bat passes is therefore best understood as an index of bat activity rather than the absolute number of bats in the area. Except for the bats of the genus Myotis, each species has a spectrogram which is usually distinctive. 2.3 Limitations of the Survey There are several factors that may affect the results and comparison between the routes: Differences in the range of individual bat detectors individual detectors of the same type can vary in range depending on factors such as local environmental conditions and battery strength. Changes in environmental conditions such as weather can be compensated by carrying out the surveys at the same time on the same night, and new batteries can be used. Observer error misidentifying bat passes and counting the number of bat passes The standard procedure for counting bat passes was followed; however there is scope for error if more than one bat of the same species / genus is passing the bat detector at one time. There is also the potential to misidentify species, particularly if the call is faint. Human error in one two transects no analysable recordings were obtained. In that situation we have relied on the written notes. There is a lower level of confidence in the identification of the species missed in this way but given the experience of the recorders concerned we considered it appropriate to accept their identification even though it could not be subjected to objective verification by sound analysis. 4

5 There is a greater danger of inaccuracies in identifying species from bat passes from heterodyne recordings, and individual bat passes are more difficult to distinguish if more than one bat is flying past the bat detector at the same time resulting in counting errors. There is also a greater risk that bat species echolocating at different frequencies may be missed, for example, heterodyne detectors are unlikely to pick-up both a Noctule Bat pass and Lesser Horseshoe Bat pass at the same time as the difference in frequency is too large if the detector is tuned to either the lower or higher end of the spectrum. On a third transect the team missed their route during Walk 4. These anomalies are explained in the appropriate comments. Faint recordings on a number of transects some of the echolocation calls on the recording were too faint to identify the bat species. Faint recordings also make it difficult to extract a peak frequency for the echolocation calls of pipistrelle species. Where the genus of bat was uncertain the recording is marked in the report as bat species and where there is sufficient confidence to assign a recording to the genus Pipistrellus but not to a species the recording is marked as pipistrelle species. Figure 1: Map of the bat transects undertaken as part of the Blackdowns Big Bat Survey 3. RESULTS AND SOUND ANALYSIS 3.1 Overall summary As in all three previous surveys the most frequently recorded bat species was the Common Pipistrelle. This species represented 63% of all bat passes recorded. There have been more passes by Soprano Pipistrelle in each year and they now represent 14.5% of passes. There were slightly more passes from Soprano Pipistrelles than Myotis sp. but those two groups were much more frequently recorded than any other species. As in previous years big bats were less in evidence although Serotines were recorded at about the same level as in It raises the question of why there should be roughly twice as many Serotines in odd numbered years. One possibility might be that the reversal in 2012 and 2014 meant that the Serotines had moved on by the time the teams arrived or had not yet got there by the time the teams departed. That would 5

6 be a more probable explanation if the Serotines were recorded predominantly at the beginning and end of the walks but that is not the case. Noctules were in very short supply and there were no Leislers Bats recorded. The number of Barbastelle passes was comparable to 2013 but only half of the recordings in Longeared bats (Plecotus sp.) are generally difficult to record due to their tendency to use passive hearing to catch prey rather than echolocation, but some passes were assigned to that genus with a reasonable degree of confidence. The Brown Long-eared Bat (Plecotus auritus) is undoubtedly under-recorded using this methodology. There are relatively close records for Grey Long-eared Bat (Plecotus austriacus) from Yeovil, and it should not be assumed that the Long-eared Bat passes were solely from the more common Brown Long-eared Bat. More bats were recorded on open moorland than in the first two years of survey and this is probably the effect of both 2013 and 2014 survey nights having been very warm and quite still. Bats will go where the insects are and on hot calm nights the insects are more likely to be flying away from the trees. The 2014 survey recorded the largest number of passes of Lesser Horseshoe Bats (Rhinolophus hipposideros) so far. In comparing total numbers however it must be remembered that 2011 featured data from 12 transects only not 16 as in the three subsequent years Table 1 shows the number of bat passes and proportion of total calls for all the species recorded, and the following maps show the cumulative presence of species recorded across the Blackdown Hills. The results only show presence of bats identified from the recordings and cannot indicate the absence of a particular species as the survey does not cover the entirety of each square kilometre, and, as a consequence, there is the possibility that species may have been missed. Table 1: Number and proportion of bat passes recorded for each species / group. Species / Species Group 2011 Bat Passes 2011 Total (%) 2012 Bat Passes 2012 Total (%) 2013 Bat Passes 2013 Total (%) 2014 Bat Passes 2014 Total (%) Lesser Horseshoe Common 45 Pipistrelle Soprano 55 Pipistrelle Pipistrelle sp Serotine Noctule < Leisler's < Myotis sp Long-eared bat sp Barbastelle < Unidentified bat species TOTAL

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11 3.2 Bat passes recorded along each transect route The recordings from each transect were analysed separately and divided into the walk and stop sections shown in the following tables and maps. It is, of course, impossible to draw any firm conclusions from data collected on one night only and the following observations must be treated with caution. Four years of surveying can however allow some tentative comparisons and at least show those areas which appear to be consistently full of bat activity. 11

12 3.2.1 Transect 1: Buckland Wood and Quants Year Bat species Transect section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total Pipistrelle Myotis sp Unidentified bat passes * Lesser Horseshoe Pipistrelle Myotis sp Unidentified bat passes Lesser Horseshoe Pipistrelle Pipistrelle 1 1 Myotis sp Serotine 5 5 Unidentified bat passes * 45 Pipistrelle Myotis sp * The 2012 and 2014 surveys were completed in reverse starting at Stop 6 and finishing at Walk 1. The recordings for this transect could not be analysed because of some equipment failure. The results are therefore based on heterodyne data only and therefore subject to the reservations mentioned previously. Species other than the Pipistrelles and Myotis ones are likely to have been missed because they are echo-locating at different frequencies. That is particularly true of Lesser Horseshoe Bats which were recorded at Walk 1 in 2012 and Passes were noticeably fewer in 2014 and 2012 than in the other two years. Is this an effect of the reversal of the walk? If the passes were concentrated at one or both ends of the transect that would be an obvious inference but the key part of this transect in every year is the central section from Walk 2 to Stop 3. The results for Walk 2 in 2013 look anomalous and future surveys may confirm that. 12

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14 3.2.2 Transect 2: Sampford and Black Down Commons Year Bat species Transect section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total Pipistrelle Myotis sp Serotine Unidentified bat passes * 45 Pipistrelle Pipistrelle sp Pipistrelle Pipistrelle Pipistrelle sp Myotis sp Unidentified bat passes * 45 Pipistrelle Pipistrelle Serotine Myotis sp Unidentified bat passes * The 2012 and 2014 surveys were completed in reverse starting at Stop 6 and finishing at Walk 1. As in 2013 most of the passes were in the central part of the transect over the open heather moorland. This was not the case in the first two years and the contrast between 2012 and 2014 is particularly striking. It seems likely that when the weather is warm and still there is an abundance of small moths and flies over the heather which the bats can exploit. If it is colder or windy the insects are more likely to be concentrated in the shelter of the wooded parts. It is encouraging to see Serotine recorded here again. The dominance of Common Pipistrelles makes one wonder what roosts there are in the neighbourhood. 14

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16 3.2.3 Transect 3: Bolham Water Year Bat species Transect section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total Pipistrelle Pipistrelle Myotis sp Serotine 5 5 Unidentified bat passes * 45 Pipistrelle Pipistrelle Pipistrelle sp Myotis sp Unidentified bat passes Pipistrelle Pipistrelle Pipistrelle sp Myotis sp Unidentified bat passes * 45 Pipistrelle Pipistrelle Myotis sp Unidentified bat passes * The 2012 and 2014 surveys were completed in reverse starting at Stop 6 and finishing at Walk 1. This transect is generally bat-rich except at Stop 3 where only 3 passes have been recorded in 4 years. That stop is at the top of a large field of improved grass and is unlikely to have the abundance or diversity of insects to be found elsewhere. In the first 2 years the bats were concentrated in Walk 5 to Stop 6, but now they seem to be much more evenly distributed. Apart from the low count in 2011 Myotis bat passes are very consistent but Soprano Pipistrelles unpredictable. The latter species went from 4 passes in 2011 to 76 in 2013, so 2014 s figure of 35 may be thought a reasonable average. 16

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18 3.2.4 Transect 4: Castle Neroche Year Bat species Transect section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total 2011 Lesser Horseshoe Pipistrelle Pipistrelle Pipistrelle sp Myotis sp Barbastelle Unidentified bat passes * Lesser Horseshoe Pipistrelle Pipistrelle sp 1 1 Myotis sp Serotine 2 2 Unidentified bat passes Pipistrelle Pipistrelle Pipistrelle sp Myotis sp Serotine Barbastelle Unidentified bat passes * 45 Pipistrelle Pipistrelle Pipistrelle sp Myotis sp Long-eared bat sp 2 2 Unidentified bat passes

19 * The 2012 and 2014 surveys were completed in reverse starting at Stop 6 and finishing at Walk 1. Two passes from Long-eared Bats are notable but no Barbastelles, Serotines or Lesser Horseshoe Bats were recorded. Common Pipistrelles are present throughout the transect. Myotis species were represented by only 2 passes the last time the transect was walked in this direction, 2012, were up to their second best total at 31 passes. Castle Neroche wood is the remains of a vast ancient forest and contains a number of large mature trees as well as a forestry plantation. It is therefore surprising that we have not heard Noctules there. 19

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21 3.2.5 Transect 5: Otterford Lakes Year Bat species Transect section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total Pipistrelle Pipistrelle Myotis sp Noctule Serotine Unidentified bat passes * 45 Pipistrelle Pipistrelle Myotis sp Serotine Long-eared bat sp 1 1 Unidentified bat passes Pipistrelle Pipistrelle Pipistrelle sp 2 2 Myotis sp Noctule 1 1 Unidentified bat passes * 45 Pipistrelle Pipistrelle Pipistrelle sp 2 2 Myotis sp Serotine Barbastelle 1 1 Unidentified bat passes * The 2012 and 2014 surveys were completed in reverse starting at Stop 6 and finishing at Walk 1. 21

22 This transect posed the best sort of problem. At Stop 1 there was a continuous noise from at least two bats at a time from two or even three species. The recordings are continuous and the concept of a separate pass on which these totals are based becomes almost meaningless. The figure quoted in the table is an absolute minimum but the real total could be eight times as great. This transect has a section from Stop 3 to Stop 4 which is consistently quiet. It is largely along a road bordered on one side by forestry and open on the other which is not considered to be optimum bat habitat. Conversely the wet areas at Walk 1 to Walk 3 are ideal for bats and as busy as anywhere in the survey. Barbastelle was recorded for the first time but no Noctules even though there are historical records of them feeding over the water. It is interesting that the numbers are comparatively low in 2013 compared with all the other years, and there is no obvious explanation. 22

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24 3.2.6 Transect 6: Staple Hill Plantations Year Bat species Transect section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total Pipistrelle Myotis sp Serotine Unidentified bat passes * Lesser Horseshoe Pipistrelle Myotis sp Unidentified bat passes Pipistrelle Pipistrelle 4 4 Myotis sp Serotine 4 4 Unidentified bat passes * 45 Pipistrelle Pipistrelle Not Myotis sp recorded Serotine Unidentified bat passes 1 1 * The 2012 and 2014 surveys were completed in reverse starting at Stop 6 and finishing at Walk 1. There was a problem with recording Walk 1, but that section has never been very productive. The totals for this transect are always low but they show a consistency which is found in few other transects. The Lesser Horseshoe Bat recorded in 2012 has not appeared again and Soprano Pipistrelles were not present in the first two years but otherwise there are only slight differences from year to year. Entirely predictably the bats seem to be mostly at the bottom of the hill where it is more sheltered.. 24

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26 3.2.7 Transect 7: Thurlbear Year Bat species Transect section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total Pipistrelle Pipistrelle Pipistrelle sp 1 1 Myotis sp Noctule Serotine Unidentified bat passes * 45 Pipistrelle Pipistrelle This portion of the survey was Pipistrelle sp 1 1 missed in 2012 Myotis sp Unidentified bat passes Pipistrelle Pipistrelle Pipistrelle sp 1 1 Myotis sp Serotine Noctule * 45 Pipistrelle Pipistrelle Myotis sp Barbastelle 2 2 Unidentified bat passes * The 2012 and 2014 surveys were completed in reverse starting at Stop 6 and finishing at Walk 1. 26

27 The totals for 2014 seem extremely low and it is difficult to see why that should be so. We need more data in the next one or two years to see if there is a decline or whether this year was an unexplained anomaly. The last time the transect was walked in this direction there were 121 passes recorded even though the first 4 sections were omitted. This year for all 12 sections the total was only 37. Were the bats all further away? In the past it has been noted that bat activity in the wood itself tends to increase if the weather deteriorates. It may be that the night was too nice. The difference appears to be almost entirely in Common Pipistrelle passes. The Myotis figures are good and it is always possible that these include some Bechsteins Bats as this species is now known to breed in Thurlbear wood.. 27

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29 3.2.8 Transect 8: Dunkeswell Year Bat species Transect section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total Pipistrelle Pipistrelle 3 3 Myotis sp Noctule 2 2 Serotine Unidentified bat passes * 45 Pipistrelle Pipistrelle Myotis sp Noctule 1 1 Long-eared bat sp Unidentified bat passes Pipistrelle Pipistrelle Pipistrelle sp Myotis sp Serotine Noctule 1 1 Unidentified bat passes * 45 Pipistrelle Myotis sp Serotine 2 2 Barbastelle Long-eared bat sp 2 2 Unidentified bat passes * The 2012 and 2014 surveys were completed in reverse starting at Stop 6 and finishing at Walk 1. 29

30 Barbastelles were recorded in 4 different sections of this transect. The results for Common Pipistrelles and Myotis bats are puzzling. These species seem to do better in odd years (2011 and 2013). The concentration of passes in those years are in the central part of the transect and in 2012 and 2014 at both ends. It is difficult to avoid the conclusion that this is a factor of the time at which each section is reached. The central part is at lower altitude and less exposed but the difference here is not the weather influenced difference noted at, for example, Transect 2. We do not know where the nearest bat roosts are to this transect and it may have an effect on how early in the night the bats foraging and communting through this area. 30

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32 3.2.9 Transect 9: Yarcombe Year Bat species Transect section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total Pipistrelle Pipistrelle 3 3 Myotis sp Serotine Barbastelle Unidentified bat passes * 45 Pipistrelle Myotis sp Serotine 3 3 Unidentified bat passes Pipistrelle Pipistrelle Myotis sp Serotine Unidentified bat passes * 45 Pipistrelle Pipistrelle Pipistrelle sp Myotis sp Noctule 1 1 Unidentified bat passes * The 2012 and 2014 surveys were completed in reverse starting at Stop 6 and finishing at Walk 1. This transect recorded its lowest number of Common Pipistrelle passes ever including none at all between Walk 5 to Stop 5. When this transect was last walked in this direction in 2012 that part recorded 145 Common Pipistrelle passes. What was special for that species in 2012? Are the Common Pipistrelles feeding somewhere else when it is warmer or were they behaving differently because of the impending thunderstorm or the gathering mist? Mist need not affect an animal that hunts by sound but it may well affect the behaviour of the insects. 32

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34 Transect 10: Membury Year Bat species Transect section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total Pipistrelle Pipistrelle Myotis sp Noctule Leisler's 5 5 Serotine Unidentified bat passes * Lesser Horseshoe Pipistrelle Pipistrelle Pipistrelle sp Myotis sp Serotine Unidentified bat passes Pipistrelle Pipistrelle Pipistrelle sp 1 1 Myotis sp Serotine Noctule Unidentified bat passes * 45 Pipistrelle Pipistrelle Myotis sp Serotine * The 2012 and 2014 surveys were completed in reverse starting at Stop 6 and finishing at Walk 1. 34

35 There were Serotines but the Nyctalus species of big bat were not recorded. Noctules were found in 2011 and 2013 and Leislers also in 2011 but neither in the even years of 2012 and When they are recorded it seems to be at the first part of the transect at Walk 1 to Stop 1. In 2012 and 2014 that is the part that is reached last and in this case it is reasonable to assume that Noctules, which are one of the earliest to emerge of all our species, have moved on by the time Walk 1 is reached. Conversely the Pipistrelles seem to be in the middle of the walk in every year. There were fewer Common Pipistrelles this year but the number of Soprano Pipistrelle passes is fairly consistent. 35

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37 Transect 11: Wambrook Year Bat species Transect section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total 2011 Lesser Horseshoe Pipistrelle Pipistrelle Myotis sp Noctule 1 1 Serotine Long-eared bat sp 3 3 Unidentified bat passes * Lesser Horseshoe Pipistrelle Pipistrelle Pipistrelle sp Myotis sp Unidentified bat passes Lesser Horseshoe Pipistrelle Pipistrelle 1 1 Myotis sp Serotine 1 1 Leislers 1 1 Unidentified bat passes * Lesser Horseshoe Pipistrelle Pipistrelle Pipistrelle sp Myotis sp

38 Serotine 4 4 Unidentified bat passes * The 2012 and 2014 surveys were completed in reverse starting at Stop 6 and finishing at Walk 1. The number of passes on this transect is never large but the pattern with Common Pipistrelles in particular is remarkably consistent from year to year. The Lesser Horseshoe Bats are recorded near to a known maternity roost although observation at that roost suggests that the majority of the bats fly off away from the direction of the transect. Soprano Pipistrelles are more confusing but the 2014 total of 11 passes is encouraging after only one pass recorded in The Leislers Bat recorded in 2013 has not reappeared this year but it is a species which is still comparatively rare in Somerset. 38

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40 Transect 12: White Staunton Year Bat species Transect section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total Pipistrelle Pipistrelle Myotis sp Noctule 2 2 Serotine Unidentified bat passes * 45 Pipistrelle Pipistrelle Pipistrelle sp 1 1 Myotis sp Serotine Unidentified bat passes Pipistrelle Pipistrelle Pipistrelle sp 4 4 Myotis sp Serotine Unidentified bat passes * 45 Pipistrelle Pipistrelle Pipistrelle sp Myotis sp Serotine Long-eared bat sp Unidentified bat passes 1 1 * The 2012 and 2014 surveys were completed in reverse starting at Stop 6 and finishing at Walk 1. 40

41 There was a problem in the part of the transect between Walk 4 and Stop 6 and it is possible that the assignment of recordings to the different sections is not entirely reliable. Any comparison with previous years needs to be made with a slight degree of caution. Nonetheless the totals are more or less what one might expect. Soprano Pipistrelles and Myotis bats seem to be recorded more in 2012 and 2014 than in 2011 and 2013 suggesting another case in which the time at which the relevant sections are reached is affecting what bats are present. The effect is most noticeable at Walk 6 to Stop 6 which is the first part in even years and the last in odd ones. The bats seem therefore to get there relatively early and move on elsewhere by an hour and a half later. The Long-eared bat recordings are a welcome addition. 41

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43 Transect 13: Broadhembury Year Bat species Transect section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total 2011 This transect was not undertaken in * 45 Pipistrelle Pipistrelle Pipistrelle sp Myotis sp Serotine 2 2 Unidentified bat passes Pipistrelle Pipistrelle 1 1 Myotis sp Serotine Unidentified bat passes * 45 Pipistrelle Pipistrelle Pipistrelle sp Myotis sp Serotine Unidentified bat passes * The 2012 and 2014 surveys were completed in reverse starting at Stop 6 and finishing at Walk 1. All species recorded more passes in 2014 than in 2013 and the only section which seems really short of bat activity is Stop 3. This could be because that point is at the highest altitude on the transect and even on warm, still nights may be less insect-rich. If 2013 and 2014 appear to be broadly similar the level of Common Pipistrelle activity in 2012 is very different. Further data are required so see if that year was exceptional. If that level of activity is not repeated we are left with the puzzle of why 2012, particularly Walks 2 and 3, was so busy. 43

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45 Transect 14: Upottery Year Bat species Transect section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total 2011 This transect was not undertaken in * 45 Pipistrelle Pipistrelle Pipistrelle sp Myotis sp Serotine Barbastelle 2 2 Long-eared bat sp 1 1 Unidentified bat passes Pipistrelle Pipistrelle Pipistrelle sp 1 1 Myotis sp 1 1 Serotine Unidentified bat passes * 45 Pipistrelle Pipistrelle Myotis sp Serotine 1 1 Barbastelle 1 1 Unidentified bat passes * The 2012 and 2014 surveys were completed in reverse starting at Stop 6 and finishing at Walk 1. Unlike the previous transect with this one all species recorded a slightly lower number of passes than in 2013 but, like transect 13, we have an apparent anomaly in Common Pipistrelles in passes in 2014 is low after 125 in Neither is anything like the 560 passes in Why should that be and are we likely to see another year like that? It is, of course, impossible to tell whether these results mean fewer bats or just less activity. There is a re-appearance of Barbastelle. 45

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47 Transect 15: Cotleigh Year Bat species Transect section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total 2011 This transect was not undertaken in * 45 Pipistrelle Pipistrelle 3 3 Myotis sp Serotine Pipistrelle Pipistrelle 1 1 Myotis sp Serotine 1 1 Unidentified bat passes * Lesser Horseshoe Pipistrelle Pipistrelle Pipistrelle sp Myotis sp Serotine Unidentified bat passes * The 2012 and 2014 surveys were completed in reverse starting at Stop 6 and finishing at Walk 1. The number of Myotis bat passes is down but these bats are consistently found in the same part of the transect whichever way round it is walked. Two passes from a Lesser Horseshoe Bat are a surprise and would suggest that there is a roost to find somewhere near. Lesser Horseshoe Bats can travel 5 miles or more to feed but tend to do most feeding quite close to the day roost. The number of Common Pipistrelle passes has increased in each of the 3 years but the Soprano Pipistrelle number is very different from either 2012 or Why are there more and will the next year see single figures again or maintain a figure in the 80s? 47

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49 Transect 16: Netherclay Year Bat species Transect section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total 2011 This transect was not undertaken in * 45 Pipistrelle Pipistrelle Myotis sp Noctule 1 1 Unidentified bat passes Pipistrelle Pipistrelle Myotis sp Serotine Noctule 1 1 Unidentified bat passes * 45 Pipistrelle Pipistrelle 1 1 Pipistrelle sp Myotis sp Serotine Noctule Unidentified bat passes * The 2012 and 2014 surveys were completed in reverse starting at Stop 6 and finishing at Walk 1. There was a problem with the recordings and these data for 2014 are based on heterodyne detection recorded on a written form. It is quite common for the number of passes to be under-estimated on the form but even so the difference in all Pipistrelle species between 160 in 2012, 154 in 2013 and a mere 36 in 2014 is noteworthy. Were the figures for Pipistrelles higher one might suspect that the lower Myotis number was a result of mis-identification but there seem to be many fewer small bats all round. There are problems hearing the large bats in heterodyne and further problems in identifying them to species level. Nonetheless the total for Serotine fits quite well with previous years. 49

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