News from Chris Dieck
'We carried out our third visit to the boxes at Burnbake campsite this last weekend. Last time out we had a common and a soprano pipistrelle. Could we go one better?
We found a soprano pip whose thunder was slightly stolen by the discovery of a male Bechstein's! In total five of the sixteen boxes are showing signs of being used, which is great for boxes that have only been up since April.
We'll be visiting again in early September, details to follow.'
'On Saturday, we checked our bat boxes at Burnbake once more and while we did not find our Bechstein's bat again, we did get 12 soprano pips and 2 common pips over six boxes, with a further box showing signs of occupancy by a number of species.
Not a bad return from 16 boxes!
If the weather stays warm, we will carry out one more check in October sometime, so keep your eyes out for news about that, although if we get an early cold snap we'll leave the bats alone until spring.'
'On our last box check of the season at Burnbake Campsite, we recorded our best haul of bats to date. 17 bats; mostly sop pips with a few common pips were found in the 16 boxes. That's better than 1 bat per box!
Furthermore, we now have signs of bats using 11 of the boxes, which is just phenomenal.
In total we have found three species in our boxes, as well as a few signs that some long-eared bats have been in residence, as well.
Not too shabby, I think. Thanks to everyone who came along and helped out. Hope to see you in the spring when we start again.'
News from Jan Freeborn
'We had a good night out at the Moot until rain stopped play. There were lots of bats around and despite having to pack up earlier than planned because rain set in, we set up two mist nets, including the triple high system (out for the first time) and captured a female Soprano pipistrelle which looked like it had bred for the first time this year.
The Moot is an interesting site down by the Avon with woodland yet to be explored and an easy walk in to the survey sites. More visits are planned this summer and details of these will be circulated.'
'We had a bit of success at Upton last night. We caught three Pipistrelles which flew into the nets just as it started to rain. I think they were running for cover under the trees (then the rain stopped!). Two managed to escape from the net as I was taking the other bat out. This turned out to be a juvenile female Common pipistrelle (joints of wing bones not fully calcified) so it looks like there is a breeding population of this species at the Park.
There will be more surveys this summer at Upton in other parts of the Park which have not been surveyed before.'
News from Nick Tomlinson
'A great evening in Hibbitt Wood (thanks DWT), with 7 bats of three species including a juvenile female Bechstein's bat, which was, to say the least, pretty cool! The woodland is around 3km as the bat crow flies from Brackett's Coppice, so who knows if this is one of Colin's as yet unringed females. We've got the odd space left on the dates to come (15th & 29th August, 12th, 20th and 26th Sept and 4th Oct) so do please let me know if you'd like to come along.
We also went out to our 'proto Bechstein's site, today, and ringed another dozen or so juveniles so hopefully it looks like this will turn into a long-term monitoring project. There are still places left on the 20th September visit, so please let me know if you are interested.'
'We had a great night in the woodland on Friday 15th, with 8 bats caught of 4 species, with a great opportunity to compare Whiskered with Daubenton's, so really re-inforcing the 'small myotis' idea. We also had brown long-eared and common pipistrelle. The latter was a male, in full breeding condition, which was really quite impressive, and we had females of the other three, all post-lactating, so they had bred somewhere reasonably nearby, if not within the woodland itself. Thanks to Chloe, Emily, Lesley, Sarah and Stuart for their help and conversation (and especially to Lesley for the home-made chocolate cake!)
Swarming on Saturday 16th was a little slow. Mostly, I suspect, because of the wind which when we got back up to the cars was blowing a hooley, so I suspect the bats had taken one look at the weather and gone back to bed. Amongst our four bats we did catch we did, however, have a grey long-eared, which was rather nice, giving us a chance to look at some of the diagnosic features, including the shape of "one part of its anatomy" (it was a male!). Thanks to Chloe, Colin, Jackie, Pete & Stuart for their help and conversation and, as I only had four hours sleep on Friday before doing a water vole survey training course in Taunton on the Saturday, then rushing back for the swarming, a special thanks to them all for putting up with a very sleepy me!'
'Thought you might like an update on where we have got to with ringing at Ryewater Nursery (in north Dorset).
So far this season we have caught and ringed 38 Bechstein's bats (and a barbastelle!), 35 of which were female and 3 were male (all immature). Of the total number of bats ringed 12 were immature, so around one third. The low numbers of males caught is at first surprising but, with only around half of all bats ringed being seen again, we are clearly only dealing with part of the total colony, the rest have bred, or at least roosted, somewhere else. We have caught females in surrounding woodlands in previous surveys, and the woodland at Ryewater is toward the edge of a large inter-connected block of woodland, so there may well be suitable conditions elsewhere. We are planning to put a hibernation box up on the site over the winter, which might draw the whole colony together next year to give birth, as it does at Brackett’s, so we may have a better idea of just what size the colony actually is then.
It is interesting to note that the colony is at least roosting within an active hazel coppice but whether they are foraging there is still up for question. There is a deal of debate at the moment as to the impact of coppice on woodland bats, with somewhat of a focus, perhaps naturally, on Bechstein's, so anything that we can add to that discussion would be great. We have applied for a radio tracking licence and hope to put that to use looking at where these bats forage, as well as roost, so gaining a valuable insight in the colony’s use of not only the surrounding landscape, but the coppice woodland within which this group of bats are currently being studied, so watch this space...'
'We went out surveying in a woodland on Friday, and caught five bats of four species (!), including a male Bechstein's. It was good to be out in the woods again, and the brilliant company and, as ever, the conversations were great (though I am less sure about Jan's jokes!!). My thanks to Alex, Chloe, Chris, Dale, Jan, Pete, Steve and Sarah for a great night.
Across the weekend's bat box checks we found 149 bats, of six species, brown long-eared (57), Natterer's (48), noctule (11), common pipistrelle (14), soprano pipistrelle (10) and Bechstein's (9). We also ringed three new Bechstein's, and found some old friends, which was great. There will be a short write up of the summer's ringing in the next newsletter. We also saw tawny owl, fallow deer, some interesting fungi and (new to me) Roesel's Buch Cricket, but star of the show has to be the red kite right at the end. On the Sunday we also found an abondoned bee hive, still stuffed full of honey - what a fantastic sweet treat that was on an energy sapping day! My thanks to Angela, Chloe, Chris, Claire, Colin, Dale, Jackie, Jon, Pete and Sarah, for great conversation, laughs and a lot of hard work. My special thanks to Dale, Chris, Sarah and Chloe for carrying the ladder for me (I know, what a wimp!) and to Pete who helped me look for, and find, my car keys, which involved around an hour's walking down (and then back up!) a steep woodland track that we had only just walked up, having thought we had finished (although a red kite right at the end sort of made up for it!).
I have been looking through our records for the bat box checks. We started checking the first woods in 2002, picking up others along the way, until we now check seven woods with a total of 261 boxes between them. Up until this weekend, we have carried out 4763 individual bat box checks, and found a total of 1,671 bats, of seven species (common pipistrelle, soprano pipistrelle, Daubenton's, Natterer's, Bechstein's, noctule, brown long-eared). In that time we have had 449 positive bat box checks (e.g. a check where we find bats, regardless of how many) so meaning that, on average, across all sites and across all checks, we find bats on every 13th box check (we find evidence of bats, e.g. droppings, much more frequently). On the best site we find bats every sixth box we check, and on the worst we have to check, on average, 26 boxes before we find bats, so quite a range - how do others compare?
We will be doing some repair work over the weekend of the 29/30 November so, if you fancy giving us a hand, just let me know (
'We popped out to Winspit for our next to last swarming visit of the season. In contrast to the early sessions there was almost no wind and we got loads of bats as a consequence, 80 in fact, between 19:30 and midnight. Species numbers were 7 common pipistrelle, 40 Natterer's, 5 Bechstein's, 2 whiskered, 3 serotine, 2 greater horseshoe, 1 barbastelle and 20 brown long-eared, 80 bats in total. From a quick look through the records I don’t think we have had a night so dominated by one species (Natterer's, at 50% of the catch!) and long-eared, at 25% of the catch were certainly well represented. My thanks to Pete, Matt, Dominic, Dale, Chris, and Clare for their help, company and hard work.
We have done five visits this year so far, with 3 bats of two species on the first, four bats of four species on the second (of which one was a grey long-eared!) and four bats on the third (all Brandt's!). This was all due to pretty bad wind conditions, which meant the bats simply could not get there! Things then picked up with 20 bats of 7 species on the third then our bumper crop of 80 bats of 8 species on Friday (by the way that worked out at an average of a bat every 4 minutes for 5 hours!), it was a busy night, so here's hoping the same happens the next time!
So far this year we have caught 112 bats, as against 263 by this time last year - just shows you what a significant impact the weather can have. It is also interesting, on a quiet Sunday morning, to play with the numbers and see if there is anything they can tell or suggest to us...
Studies so far (both ours and elsewhere) have shown that very few bats are re-captured, either on the night or across nights, suggesting, essentially, that bats visit a swarming site for one night only.
Swarming lasts, nominally, from mid(ish) August until early October, something like 9 weeks (it will stretch earlier and later than this, but this is probably the core period). If we assume (just plucking random numbers out of the air) that on 4 nights in any given week the weather conditions are suitable (and the weather this year suggests that is probably an under estimate, but let’s go with it anyway), that gives us 36 nights when there will be activity at the caves.
Looking at the figures from our catches so far (over four years), and taking out the three nights where we had bad weather (conditions not experienced in prior years) an average catch would be around 50 bats a night. Of course we do not know what the total number of bats using the caves on a given night is, but (again, from our own work and that of others) we can be pretty certain that the bats we catch are pretty much all individuals, (eg our re-capture numbers are low) so we can, for simplicity, assume that we catch every bat that uses those caves, which means we catch 50 unique bats each session.
If we work that all out it means that, as a minimum, there are at least 1,800 bats using those caves over the swarming season and the true numbers might be very much higher, as there are some crude assumptions above!
Equally, the caves at Winspit are only one set of caves/mines in the Purbecks, and studies have shown that there is very little interchange across swarming sites, so we can assume that bats using one cave to swarm do not use one of the others.
Looking at the work that John Flanders did, our catching rate at Winspit is around twice the rate he found at the sites that he surveyed, but we need to be careful in comparing methods, as he was using harp traps and we are using mist nets, which almost certainly will greatly increase our capture rate compared to his, but that to one side, Jon clearly showed that at least five other sites are important for swarming bats, and he did not survey all the sites that exist within the Purbecks.
So, where does that take us? Well, taking all that together (including with some big assumptions, I grant you!) there might be getting on for 8,000 - 10,000 bats using the mines and caves in the Purbecks for swarming in a given season - I wonder what percentage of the county's population that is?
Some studies have shown that bats will fly 30+ kilometres to reach a swarming site, meaning that Winspit, and others, might be bringing bats in from as far a field as Dorchester, Blandford and even just into Hampshire.
Now swarming is believed to be a crucial aspect of the ecology of some species (the swarming species are defined as the myotis, plecotus and barbastelle species, yet other species occur, reasonably regularly, at swarming sites and for some, for instance serotine, we do not truly understand their breeding strategy) so sites that support swarming are important.
Now we have known for sometime that the caves and mines in the Purbecks are important for hibernating greater horseshoe bats, indeed many are grilled for exactly that reason, but we knew little else about their importance for other aspects of bat ecology. Even though the above is filled with speculation, and the numbers/assumptions are up for debate, I do think it suggests that Winspit, and indeed the caves/mines in Purbeck in general, are amongst some of the most important bat sites in Dorset for far more of our bats' lifecycles than we first thought…'
"Well the summer survey season comes to a close, with a woodland in which we caught two brown long-eared, and a swarming survey where we only caught 11 bats (mind you, there were four species, inclding a Brandt's, five if you count the GHS that got out of the net!). My thanks to Andrew, Angela, Chloe, Chris, Colin, Dominic, Emily, Jan, Mark, Pete, Sarah, Stuart and Tom, for their help, support and great conversation.
It has been a mixed year, with some exciting finds (a new record for Bechstein's, which might, possibly, be a new colony?) and some grest results (one night's swarming had 80 bats, and we ringed 41 Bechstein's at Ryewater, but it was over way too fast. The winter surveys are heading our way and we are already starting to plan for next year. The dates for batbox checks, Ryewater and swarming have already been circulated and we will have some dates for woodland surveys shortly (nothing like being prepared). We have also secured the radio tracking licence that we applied for a while ago, so we will be organising a couple of surveys in West Dorset to find out a little more about our Bechstein's bats, watch this space for more information."
'I thought I would do a bit of a rough calculation on the number of people involved and the hours put in to the surveys that I am involved with, so here goes….
Over the course of the summer a total of 39 individuals have been involved with the survey work. In that time those volunteers have put in over 580 hours of volunteer time, equating, approximately, to 72 working days, or FOUR AND A HALF working months! If we cost that at, say, a rate of £100 a day, which I think is the mid-range volunteer day rate when you are calculating the value of volunteer time for Heritage Lottery Fund applications, that means something like £7,300 worth of time - simply amazing when you look at things that way. Of course, this is only one set of surveys that take place, there are loads more. Neither does it include the time put in to running the group, maintaining the website, arranging and attending meetings, writing newsletters, sending out emails etc.
As far as the surveys I have been part of, we have caught/seen; 33 common pipistrelle, 15 soprano pipistrelle, 167 Natterer's (!), 4 Daubenton's, 23 noctule, 5 serotine, 98 Bechstein's, 6 whiskered, 2 greater horseshoe, 5 Brandt's, 3 barbastelle, 116 brown long-eared & 1 grey long-eared, some 478 bats in total of 13 species - not a bad year, even if numbers were down on prior years! Of course many animals will be repeats, especially those on the bat box checks as they are in colonies, so perhaps we should say we have caught/seen 478 "bat events"!
Within those numbers we have ringed 48 Bechstein's, 5 whiskered, 1 Brandt's, 3 barbastelle and 1 grey long-eared.
Of course none of this would be possible without that huge volunteer input. I don’t propose to single anyone out, you all know who you are and you know we could not do it without you, but a huge thank you to all of you for carrying equipment, helping put it up (and take it down at 1AM when we are all tired), scribing, brilliant conversations, bringing cake and biscuits or simply putting up with my endless chattering!'
'Well, we went out on our first bat box maintenance session yesterday, re-numbering boxes (where the numbers had started to fade), and re-hanging with aluminium nails rather than wire (where the wire had started to cut into the trees). We also took the opportunity to errect a hibernation box at Ryewater ready for the Bechstein's colony to gather in this coming summer! It was a fantastic day, with four woodlands done and the hib box put up. We also found a few bats, noctules and Natterer's, and a couple of mouse nests (apodemus sp) so those boxes remain to be done as we did not want to disturb the animals within. Great conversation, some lovely weather and, to finish with, a tour of Clive's butterfly house, which was superb. My thanks to Pete, Carol, Caroline and Chris for their hard work and conversation. We had to postpone today's session, so will re-arrange another sometime in the early new year, when we also hope to put up a maternity box at Ryewater as well, just to see which the bats prefer.'
"We did our first Purbeck hibernation visit of the season on Saturday, in glorious weather (the view from Winspit was fantastic!) and it got off to a great start with 114 Greater Horseshoe in Port Arthur caves, a new record for the site. Vesper bats were a bit on the scarce side though, with a handful of Natterer's and Whiskered/Brandt's and a pip or two being all we saw, but the pasty and pint in the pub afterwards made for a superb end to the day's events. My thanks to Pete, Anglea, Sarah, Jackie, Emily and Lynda for their help and conversation."
"We were out doing our hibernation checks in Purbeck on Saturday (despite the weather!) and had 118 greater horseshoes, across 4 sites, with 113 the highest count (one less than last month). We also had a few scattered myotis, but fewer than I might have expected, and one brown long-eared, which I think is the first one we have ever found in the Purbeck. En route we found a Polecat on the roadside which was an interesting addition. We finished off with a beer and a pasty at the Square and Compass, which was so busy we had to stand outside to eat it! My thanks to Andrew, Carol, Chris, Jon & Pete (who was suffering badly with a really vicious bug) for a great day out."