Research
Barbastelles in Cambridgeshire
Following the discovery of Barbastelles in a woodland just outside Cambridge, a great deal of fieldwork is being carried out to learn as much as possible about these elusive bats.
A Barbastelle. Shirley Thompson
A team of bat group members have been radio tracking the Barbastelles to find out where the bats are roosting and foraging. The bat is caught in a mist net and then a tiny radio transmitter is attached to the bat enabling its movements to be followed. The transmitter is tiny and weighs only 0.35 grams. It falls off after on average 9 or 10 days.
The work has revealed the location of eleven Barbastelle tree roosts, which are all similar-sized oaks clustered in a small area of woodland. On one night a juvenile female flew 11 km from the wood in which she was tagged! A more typical distance from roost to foraging areas was around 6 km. Woodland appeared to be the favoured foraging habitat.
As a result of this work, the woodland containing the roosts and also the favoured area for foraging (an adjacent woodland) have been designated as a candidate Special Area of Conservation. This designation is given to protect some of the most seriously threatened habitats and species across Europe.
The Barbastelle Barbastella barbastellus
The Barbastelle is a medium sized bat, by British standards. It is very distinctive looking; it has black fur and ears that join over its head.
It's diet is thought to be more specialised than many of the other British bats; it consists almost entirely of moths.
The Barbastelle is rare in Britain, this is probably partly due to it's highly specialised diet and the loss of ancient semi-natural woodlands which support large numbers of moths and suitable tree roosts.
Barbastelles have been found roosting under loose, flaking bark, and artificial roost sites have been created for them by nailing pieces of carpet to trees.
Barbastelles sound quite distinctive on a bat detector, and are best heard at around 32 kHz. At this frequency the sound has been likened to that of castanets.
References
Greenaway, F. (2001)
The Barbastelle in Britain. British Wildlife, 12 (5): 327-334
Sierro, A. (1999)
Habitat selection by Barbastelle bats (Barbastella barbastellus)
in the Swiss Alps (Valais). Journal of Zoology, 248: 429-432
Bat box checking
The group monitors bat boxes that it has put up around the county.
Chris checking bat boxes.
This work enables the group to monitor populations of bats in the county.
The group uses different types of bat boxes and are monitoring the success of different designs.
The Norfolk Bat Group has some good information about different types of bat boxes:
www.norfolk-bat-group.org.uk/bb.html
The Bat Conservation Trust website gives information about how to construct your own bat box:
www.bats.org.uk/batinfo/batbox.htm
Alana Ecology is one place to order bat boxes from:
http://www.alanaecology.com/
Monitoring
Part of the long term monitoring of bats in Cambridgeshire involves keeping records of sightings of bats, hibernation counts and physiological measurements of bats.
Measuring the forearm of a pipistrelle.