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...