Bernwood Forest Bechstein's Project 2013

Another year and another season getting to know our local Bechstein's bats.  We've spent the winter getting data sorted and embarking on new projects as well.  Toby went off to Canada in December to study carnivorous bats with Brock Fenton, and was last heard of in the depths of Belize.  Jo had a baby boy in the early hours of Christmas Eve and is enjoying parenthood, but this has meant she didn't get all the records sent off to local records centres etc, as quick as she'd like, but it's nearly all done and hasn't written up notes from our winter Bechstein's knowledge sharing meeting (sorry - next job on list). Chris has been capturing great footage of otters, bats and other wildlife and coaching his local rugby team to stardom.

Surveying this year has got off to a slow start with late spring and night time temperatures barely reaching 10 degrees Celsius until this week. Hopefully we will get the chance to start some surveys in new areas this week - fingers crossed.

We have received a new NE license for 2013 and will continue to explore the how Bechstein's use the landscape around Bernwood Forest. We are also pleased to say that we continue to receive positive support and interest from local woodland owners and farmers.

We have some interesting ideas but must continue with the plans from last year which were so rudely interrupted by bad weather. We'll continue to liaise closely with other projects in the area including our colleagues in the NBBG and the High Speed Rail (HS2) bat consultants, to ensure we don't over disturb the bats.

Recent reports indicate that the HS2 ecologists caught and tagged a female Barbastelle nearby in the Greatmoor area, together with a brown long eared bat.  Colleagues in the bat group have also reported catching and radio tracking a female Bechstein's bat at Finemere Wood. All good stuff and we look forward to hearing more about this.

Don't forget to follow progress and updates here and on Twitter and hopefully we will see some of you on the surveys.  Here's hoping for better weather than in 2012!

Long summer nights,

It's probably about time for a blog update.  We had a trapping break whilst female bats were heavily pregnant, givng birth and had newborns, but we are back out and have been very busy. The past month has been particularly intense, as we've been doing two to three surveys a week across the Bernwood area (to minimise disturbance we only visit individual woodlands a maximum of three times a season, usually less, and try and spread surveys around). All the late nights do take a toll, although in Toby’s case being a student he has very flexible working hours and so has slipped into his own personal time zone - a few hours behind everyone else in the country. 

The reason for doing so many surveys - apart from having such a large area to cover, including some woods where we have not previously had access - is that we were planning to radio track Bechstein's this year, and we needed to do the surveys to catch them. For our current aims, a suitable individual to radio track would be a breeding female, with a healthy weight and condition, and in short we haven't done any radio tracking because we haven't caught a suitable individual. 

We have seen males, non-breeding females and even a juvenile (male), however we took the decision not to try tracking those bats. While all individuals are vital parts of a healthy population, we are most interested in the movements of breeding females; maternity roosts are the most valuable to find as they are used by more individuals, and possibly for longer time periods compared to the sites used by lone individuals. In addition, breeding females seem to form the core of the population, so gathering information about their foraging movements is our priority. This is not to say that we are not interested in the movements of non-breeding females or males, and certainly plan to track these individuals in the future. We had planned to track some males this year, if we already had tags on breeding females, but for now they are not top priority. 

We have had much discussion amongst ourselves, and with colleagues working on similar projects, as to the reason for the difficulties observed this year (which are not limited to the Bernwood Forest area). The primary suspect for most of our issues is the unusually wet - and often cold - weather that we have been seeing. Adverse conditions make it difficult for bats to feed, and also affects the numbers of their insect prey meaning the effect can continue even when conditions improve. This particularly impacts upon pregnant females, who need extra energy and may be able to forage only a limited distance from maternity roosts - a problem compounded by the greater density of females competing for food. 

A general effect of wet years that we observe in bats is a reduced number of pregnant females in the population. If a female cannot find enough food to support a pregnancy, it makes sense to that individual to concentrate on its own survival - bats are generally quite long lived, and so it is a good long term strategy to survive to breed again in a better year. When females are not breeding, they can disperse away from maternity roosts, thereby avoiding competition in a densely populated area, and while they may end up in a less optimal habitat they are nonetheless better off. The theory as to why we are not catching so may bats with our primary survey method (using a sonic lure to call them in) is that with fewer females breeding and greater dispersal, there is a reduced density of bats in maternity woodlands, and reduced territoriality, and so individuals are less likely to respond to investigate the social calls emitted by the lure. It is hard to come up with hard evidence to support some of this idea, but nonetheless it is an effect that has been observed in wetter years in the past and makes things difficult. 

Changing their behaviour in wet years makes sense as a long-term strategy from the bats perspective, but it's still quite frustrating for us when it means that we are unable to achieve things that we had planned for the season. What's that oft quoted phrase about working with children and animals...

We will continue surveys for next few weeks, as long as the weather allows, and while there has possibly been a certain air of pessimism in this post, I should finish by noting that this year has not been completely without success. We have added several new Bechstein's woodlands and had a great night last weekend when we were joined by a crew filming a segment for the One Show on BBC1 (watch out for a further blog post on this, and we'll share the broadcast date when it's confirmed). 

September may be creeping into view already, but our season isn't quite over yet!

Trapping Diary - Good weather for ducks?

Since I last wrote a post for the blog the bat season has begun, but it's come as more a damp thud, rather than the exciting start we were planning. This is down to the weather which has been colder, wetter and windier than we've experienced at this time in the last few years. Unfavourable weather prevents us from getting out to survey, and also when it occurs over a longer period can have a notable negative impact on the bats, which is particularly reflected in the number of juveniles for the year and perhaps the lower weights of some of the bats we've been seeing.

To read a brief report of the surveys so far, click on.

Videos

Hi all. I've been working on a new update to the blog covering the surveys that we've done so far this season. That should be done soon, but in the mean time here are a couple of videos from the surveys.

This video shows a couple of the bats we caught last night.

This video shows some footage Chris took of Bechstein's last year.

2012

Well there hasn't been too much to update through the winter months, while the bats sleep and we carry on with other responsibilities, but summer is approaching and the bat season has now begun - so we should have a lot more to say over the approaching months.

We were able to learn a great deal last year and we've tried to use that information to direct our plans for this season, which include further trapping surveys of bats in woodlands and more radio tracking. With the first bout of radio tracking pencilled in for next month, to precede the maternity period, those long field hours and sleepless nights suddenly seem very close!

In all - it's shaping up to be a fun, and hopefully productive, year for the project. We will endeavour to keep updating our blog and twitter - if you want to keep in touch you can get updates by email using the 'Follow us by email' box on the right hand side of the blog page or follow us on twitter @bechsteins!

First Year Summary

Well things have been a bit quiet on here of late. As it stands we have wrapped up fieldwork for this year; the bats are well into their autumn dispersal at the moment and with the weather getting colder the bat season is nearing a close - certainly for our surveys.

We are still working on analysis of the data, although this takes some time; particularly as we all have other commitments to attend to. However, to summarise the results from this year we have produced a brief outline of what we found.

A copy of this report can be viewed at the following link:

https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid=0B4x6uSr-8IfWMDQ1YmM1ZjYtOWJlZC00MzM4LWEwODAtNGFhNmRlY2UxYTI4&hl=en_GB

We would like to have spent slightly more time refining the document, but a couple of time pressures meant we felt it would be best to publish it today. The report was sent to a number of people relevant to some of the issues affected by the bats, I have also pasted a copy of the covering letter below the jump, so click to view that.

Radio tracking approaches the end, and something a little bit different...

Things have been a bit quiet on the blog front for the past couple of weeks, but that's not because we've been slacking off. We've been out every day and very nearly every night since we put the tags on two weeks ago (although it feels like longer), and I can't pretend there isn't a slight feeling of relief as we start to lose tags and get the chance for a brief rest - although there's still plenty to do this season.

The author listens from a hill in the dark.

As things stand; tag four seems to have failed, we haven't heard it for the past few days and it was giving an abnormal signal the last time we did. Tags one and three are still transmitting but appear to have become detached from the bats, unfortunately they don't look to be in retrievable positions. Tag two is still outstanding, we briefly heard a weak signal from it last night but couldn't detect it again or narrow down it's location. From the signal it was giving, it may also be failing, but we're hoping to check for it again today to be certain.


For some additional news; last night we decided to watch for emergence at one of the tree roosts in the wood. The roost was found in our first round of radio tracking earlier this year and Jo counted Bechstein's emerging at the recent mass count (Jo adds: And they were Bechstein's honest - I could see their ears as they crawled out and they had Myotis calls - Jo :) ). With bats emerging we decided to hand net to establish the status of the roost - although the height of the hole and the need to manover the net through several branches meant this was not a trivial endevour.

I'm not sure this picture fully belies the length of pole needed for the net, I make it around 20ft and it only reached when held up at shoulder height. Holding the net I had no view of the hole and had to be talked into position by Chris with the night vision camera.

Having caught a few bats, we got a slight surprise as the roost turned out to be a maternity colony of Daubenton's with both lactating females and juveniles in residence. As far as I'm aware, we haven't had much luck finding Daubenton's tree roosts in this area and while the change of use is not unusual it's not something we often get to record.

Juvenile male Daubenton's on release (Copyright Toby Thorne 2011)

With tracking all but over, we now have a chance to recover some sleep and then regroup and continue with the further trapping surveys and other work that needs fitting in before the end of the summer. Then at some point we also need to start thinking about how we transfer the pages of radio tracking field notes into meaningful analysis...

Mass Emergence Count

On Saturday night we were joined by a number of North Bucks Bat Group volunteers, with the aim of conducting emergence counts at all known roots, to give us a clearer idea of the numbers and distribution of the bats.

Having arrived early to make sure we had time to organise teams and take people to their roosts - some of which are harder to find than others - we then settled in to wait for the bats (time that I spent constructing a dry place to sit from surrounding, natural materials - a futile exercise as it was in the wrong place to see bats emerging).

The bats started to appear a little more than half an hour after sun set, with a total of just less than sixty being recorded across several roosts. A secondary success was the identification of the exit hole for one of the roosts, something that had puzzled us on previous visits. All in, the night was a success, and it was great to see so many people coming out to help. That said, the count didn't beat our previous highest emergence count, which was all bats from a single tree, so clearly there is a way to go yet, and more roosts to find.


Thanks to all who took part!

Radio tags are go.

With the birthing period now passed (we don't like to disturb bats when they are heavily pregnant or have young attached), we're now getting stuck into our second period of radio tracking. This should hopefully give us more information about where bats go to forage at night, both within and potentially outside the woods, as well as allowing us to identify roosts used during the day time.

The first step for this part of the project was to catch some bats to tag, and so on Wednesday night we went out to trap in one of our core woodlands. Things were initially quiet, but we then caught a Bechstein's which flew into the trap as we were stood there checking it. This was shortly followed by another Bechsteins, as well as a number of lactating female Brown-long-eared bats. Both Bechstein's were good condition and were tagged before being released. The tags are very small, weighing a fraction of a gram, and are glued to skin on the bat's back between the shoulder blades. A picture of one of the tagged bats is below and, while the tag is covered by the fur glued around it, you can see the aerial which is quite long but is extremely light and flexible, so it causes minimal interference to the bat when it is flying or crawling around in the roost.

Image Copyright Stuart Blair 2011

With the tagged bats successfully released, we returned to the wood the following day to locate them in their roost. Following the signals led quickly to the discovery of both bats together in an interesting tree roost away from the main part of the wood. To maximise the information we can gather during our tracking period we decided to tag two more bats, so returned to the roost in the evening to catch bats by hand net as they emerged. Five bats were quickly caught, with well over sixty emerging in total. After examining the five bats the two most suitable were given tags and all were released.

Image Copyright Toby Thorne 2011 
(the aerial is blurred in this picture as the bat moves to take off, and so appears larger than it actually is)

We then followed the tagged bats for a few hours, to try and establish the approximate areas that they had headed to. Three appeared to be foraging in the woodland, while the forth quickly disappeared and could not be located in the immediate area.

The next couple of weeks look set to be very busy, as ideally all bats must be located during the day to identify roosts, and we must also learn as much as we can while we are able to follow the bats at tonight. We will return tonight for some more preliminary tracking, tomorrow night we are doing emergence counts from all known roosts, with the help of volunteers from the bat group, and then next week we start on some more detailed tracking of the bats.

Not sure where sleep comes into it though...

The Press Release

Having talked about the press release, we might as well post the whole thing here. It's fairly long, so click below to see it after the jump.

...and another one!

Our press release of yesterday is already out of date, with the first check of the traps on last night's survey revealing another Bechstein's!

The wood is in the core area of the survey but not one we had visited before, so this is a new dot on the map as well as another bat. Following the initial excitement we also caught several brown long eared bats, a Natterer's and a Whiskered bat - not a bad haul.

The latest Bechstein's

The weather followed the forecast almost perfectly and the rain only became significant at 1am as we were leaving. We also had time to play with our twitter feed, which we have set up so we can update it from the field. It appears on the top right of the blog page if you want to check it out.



All in, another good night - will we ever stop finding them?

Introduction

Following the discovery of rare Bechstein's bats around the Bernwood area of Buckinghamshire as part of the Bat Conservation Trust Bechstein's project, a further study - The Bernwood Forest Bechstein's Project - has been set up by Jo Hodgkins, Chris Damant and Toby Thorne (who were all involved in the BCT study) in order to find out more.

We have been working hard for several months surveying woods in the surrounding area to get some idea of the spread of the population, as well as radio tracking to establish movements.

This effort has paid off with a remarkable degree of success, but this is not something we have been able to share widely; because of our commitment to the wishes of landowners - without whose considerable help we not have been able to do the project at all - and also the sensitivity of the information with two significant developments proposed in the area

However having written an interim report and sent out a press release on our findings so far the bat is now somewhat out of the bag. Given the interest that people have shown, and the significance of the bats, we wanted to have some means to share information and show how we're getting on - hence the creation of a blog and twitter feed for the project.

And here it is!


More information and updates to follow.