DBG Events: Middleton Field Study Centre Survey.

Every year since 1984 Durham Bat Group has carried out a count of the bats that emerge from Middleton-in-Teesdale field study centre.

In the bad old days before we had reliable detectors and the only way to identify bats was to catch them, we assumed that this was the largest Whiskered roost in the country.

However, once we were able to identify bats without catching them, we realised that there was a colony of Common Pipistrelles that lived in the east end of the main building and in the roof above the dining hall.

When school closed the building was repurposed as Middleton Centre for Outdoor Learning - later Middleton Field Studies Centre.

The FSC was closed in March 2013 as it was felt the expense of essential repairs to roof and heating were not economically viable, resulting in another change in temperature.

The survey is not trivial. There are 8 gable ends on the building and then there is the dining hall and the reverse of the building. We usually trap at two of the gables and occasionally send a more agile batworker aloft to catch outside the dining room. We also need to capture outside the exits on the eastern end of the building to investigate the use by Soprano Pipistrelles

xyz

Field Study Centre and environs Google 2014

The 2014 survey was the first time since 1984 that we failed to net any whiskered bats and the total number of Whiskered/brandts bats recorded was at an all-time low of 22. We did observe bats emerging from the building but would note that the emergence was unhurried rather than the urgent departure of lactating females . We also noted that both the Common Pipistrelles and Myotis bats emerged from a whole range of places rather than the well-defined exit points they usually use. Putting these facts together, we might infer that the only bats using the building were non-breeding animals.

xyz

Above - view from East

At the start of the evening we did notice Myotis bats flying from the town, over the building and towards the river. It is quite possible that these are members of the breeding colony. 2014 is proving to be an excellent year for bats with colonies giving birth early . In several cases they are using warm weather roosts that have not been used for decades.

xyz

Whiskered / Brandt's bat

So what has happened to the Middleton colony?

  • The first possibility is that the good weather has prompted the colony to move to a slightly cooler roost. We hope that this is the case but feel it unlikely as the colony has bred at the Field Study centre every year since 1984. Surely 2014 is not the first fine spring since then.
  • The second reason might be an extrapolation of the slow decline of the colony that we have observed since 2007.
  • The third might be something to do with the change in use. This is the first count we have carried out since the Field Study Centte closed in July 2013. It will not have been heated since then.
xyz

 Above - view from South

As yet we really do not know what has caused the decline. We will inform the county ecologist of our findings and keep our fingers crossed for 2015.

The count is always held close to the summer solstice. Please put it into your diary for next year. Noel Jackson