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Wednesday, 20 August 2008

Happy Harp Trapping!

A couple of times this year I have described my Tuttle (or harp) trap, built with the intention of creating an effective trap for harmlessly catching live bats, but smaller and more versatile than the commercially-available traps. Cheaper too! (see The Kitchen Table Harp Trap, February 2008).
Back in May I described the trap's first outing, when it was unfortunately placed over a roost entrance which wasn't in use. (See A Bat in the Hand, May 2008). As the bat maternity season started soon after that I had to wait with gritted teeth for the breeding season to end, so I could find out whether the trap worked or not.
A couple of weeks ago Lothians Bat Group had a trip to a site in the Borders and I set the harp trap up at the entrance to a Daubenton's Bat (Myotis daubentonii) roost and waited with baited breath. With 8 or 10 people waiting to get a close-up view of the bats, I couldn't help dwelling on the fact that the wretched gadget had yet to catch a bat - talk about pressure!
The first 2 or 3 bats flew past the trap, finding ways around it or even through it, causing a sweaty brow on my part. However, this is always a problem with harp trapping at a roost, so after a little work closing the gaps with coats, twigs and anything else that came to hand my fingers were re-crossed.
I got involved in a conversation and missed seeing the first bat to be caught, but yes, a bat was actually caught. My week's hard work back in the winter wasn't in vain after all! It quickly became apparent that the plastic lining of the catching bag was too long, which slowed the bat in moving into the sides of the bag, where it could not get out. In all, twelve Daubies were caught and I was able to check several of them for parasites, watched by some Group members. At the same time, other members of the Group were able to gain some valuable bat handling training.

The trap in place at the Natterer's roost (the roost is in a crevice in the wall behind)
Now that I knew the bat worked I followed up with an evening at a newly-discovered Natterer's Bat (Myotis nattereri) roost in the wall of an old farm steading, where I needed to confirm how the roost was being used. Again, the trap did it's thing and I was able to catch five bats (although a sixth was caught as I was taking the trap down). With three adult females, a juvenile male and a juvenile female, I was able to conclude that this had been a maternity colony, with the young bats now flying and the trap had earned it's place.

A juvenile Natterer's Bat

Before I next use the trap I'll trim back the plastic lining. The only other problem that has come to light is that the legs are a bit spindly and wobbly. The trap is light in weight, so the legs don't need to be too strong, so I'll delay making any changes to that for now. But at last, eight months after building it, I know the trap is fully functional and effective.

Please note, everything described above was carried out under appropriate S.N.H. licences. Trapping and handling bats can be harmful to them if not done with the correct equipment and skills. To do so without a licence is a criminal offence.

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