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Daubenton's bats are found all over Britain. Over the last few months, they have been returning to their summer roosts from their hibernation sites, which can be up to 40km away - not a great distance but when you weigh less than a shrew, it's a mammoth undertaking.
One group of bats have been studied more than any other, and those are in the beautiful Wharfedale Valley in Yorkshire. John Altringham of Leeds University has studied these bats for years as they live their lives up and down the river, from the graveyard roost in Ilkley all the way up to the roosts under the old stone bridges at the top of the dale.
This year John wants to look at the movement in and out of the roosts and the movement between roosts. Using special PIT tags and fly-through rings the team will be able to follow the movements of individual bats from one roost to another and to log the arrival and departure of specific bats. They will also be able to discover new habitats because the bats will carry tiny radio transmitters that should allow us to follow them finding new roosts.
The interesting thing about their study is they have a good history of data. That can live up to 20 years and operate across a huge landscape. John's team have a history of individuals and know where the bats were born, where they hang out as juveniles, where they existed as bachelors in groups, and then where they are today. Throughout the series we hope John will be able to comment on all these for WOTM as he sees the bats signing in and signing out of their roosts.
We had a successful night with John and the bats in Yorkshire; we encountered the Upper Dale Bats - a roost of males holed up inside an old stone bridge right at the top of Wharfedale in Yorkshire. They have already made journeys from the nursery roost, probably down in the graveyard in Ilkley, up the valley, into winter roost caves, and back to this bridge. But the question is why they are there. Have they been kicked out by more successful males lower down the valley where the insect feeding is better? Maybe these are the social outcasts of Wharfedale?
Further Reading:
Next report: Bats at the Cemetery Gates