Bat survey almost at 100% coverage

For the last four years the survey has split the island into 275 500 x 500m squares and taken sound recordings in as many as possible in both spring and autumn. Now just a handful are still available.

‘We have never had this many squares filled before and if this is our last year it would be wonderful to get 100% coverage,’ said La Societe bat section secretary Laura Harrison.

At the time of writing there were two squares available – one in St Martin’s and the middle of St Peter Port, quite possibly in someone’s back garden.

People taking part in the survey have to take two recordings – one in spring/summer and then one in autumn, with the summer window closing very soon.

‘You can get very different results when you compare the two sets of recordings,’ Mrs Harrison said.

‘In September the mating season starts and all the males are out looking for females, while the bats are in maternity roosts in June and July. The habitat usage between the two seasons can be quite distinct.’

Volunteers select their square from an online map, and place a static bat detector outside for a four-night period, once between the start of April and August, and then again at the same location before the end of the October.

The bat detector automatically records bat calls to a memory card every time a bat passes during the night.

Volunteers can borrow a bat detector kit from any one of five bat centres which contains all the instructions and equipment required to take part.

Automated sound analysis then identifies each sound recording to species and send them the initial results within a few hours.

The analysis will also identify sounds made by bush crickets and small mammals, such as shrews.

Mrs Harrison said that although their initial funding had been for four years, the team was really keen to carry on the bat survey in some form.

‘It is quite expensive to run,’ she said.

‘We would ideally like to carry on as we are and would happily speak to someone who might help with funding.’

The team are now going to do a large analysis of four years of data to see if they can on in a reduced way.

‘We need to work out how the minimum number of static recorders we would need to get a proper idea of our bat population,’ she said.

‘At the moment we think the bat population here is doing OK. We don’t have light pollution and the intensive agriculture that has led to the worldwide decline, but we really need eight years of data to prove that.

‘We will be hopefully presenting our findings at a survey in March and then perhaps working more closely with Jersey on a more pan-island approach.’

• For more information and to take part visit www.bats.org.gg.