Tuesday, 10 September 2013

Bat Walk - Saturday 14th September

We gathered at the St Ives visitor centre for our bat walk. It was a warm(ish), dry evening, which is ideal, as bats cannot “see” in the rain and so don’t come out to hunt.

British bats include 18 species – all of them quite small.  The largest is the Noctule bat which is still smaller than the palm of your hand. They are all insect-eating - or insectivorous - nocturnal, flying mammals. The most interesting thing about them is how they “see” so well in the dark that they can catch flying insects. They do this by “echolocation”, locating things by their echoes. To do this, bats make shouting sounds. The returning echoes give the bats information about anything that is ahead of them, including the size and shape of an insect and which way it is going.

As ever, the first bat was spotted before it even got dark. As with humans, it seems, there is always one breaking the rules!

We had a quick safety briefing and check on torches and checked our numbers – as we didn’t want to lose anyone when it got dark! Next we handed out bat detectors, which are small boxes which translate the bats’ high-pitched squeaks into sounds we can hear. Then, as the dark thickened around us, we set off up Cross Gates Lane behind the golf club, towards some ‘inviting’ derelict barns.

At the barns the detectors soon picked up bat activity in series of short, sharp stutters, but the bats themselves were harder to see. With a few torches up in the trees, we soon spotted the Pippistrelle bats. They were flying just under the canopy of the trees – where the branches spread over the lane to form a long high “tunnel” and the insects shelter from the breeze.

After watching and listening at the barns we moved back down the lane and on to Coppice pond, where the water attracts lots of insects and we were able to hear Daubenton’s bats - the “water bat” - moving out over the lake.

The bat species can be told apart by their behaviour and the frequency of their calls: how high or low they squeak. Though we did not find it easy to differentiate many species, there was lots of bat activity to keep us occupied.

As a bonus to the evening, one of our younger members pointed out that there were small fish close in to the lake shore and we saw a few boldly striped perch. We also saw lots of crayfish in the shallows.  These are small, fresh-water lobster-like crustaceans. Their presence in numbers is encouraging, as St Ives have undertaken work to encourage the endangered white-clawed crayfish in Coppice Pond.

There is lots of information about bats on the web, if you are interested.  Here are two for starters:
Thank you to everyone who joined us. We hope you enjoyed the event and learned lots about our bats too.

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