Clennon Gorge Nature Reserve is attached to Paignton Zoo; you can explore some of it from the nature trail that starts near the lemurs. The reserve sits on limestone bedrock, and limestone readily forms caves.
Bats have taken advantage of this scenario and have made themselves at home in these cool calm dark pockets of the reserve. So far, we have records of three species of bats using the caves through winter as a hibernation roost; greater horseshoe bats and lesser horseshoe bats and very occasionally a Daubenton’s bat. Some of these bats will also utilise the caves though the summer as a feeding roost.
Our surveys of bats in the caves goes back to 1991 and over the last seven years, we have been carrying monthly bat counts. It is important to note that these caves are only visited once a month and only under license from Natural England.
The survey itself is an interesting experience irrespective of the bats, with intriguing rock formations and fantastic invertebrates to be seen. My favourite Invertebrate is the European cave spider. They can be quite big and they create egg cases that look like perfectly spherical cotton wool balls with an orange centre. There are also moths that overwinter in the caves, such as the herald and the bloxworth snout (great name!). Another mini-beast of note is the bristletail Trigoniophthalmus alternatus, an insect restricted to caves in South Devon.
During the winter surveys, it doesn’t take long before you spot your first bat, and it tends to be the more conspicuous greater horseshoe. Their tear drop shaped bodies will be hung from the ceilings and the walls of the cave, maintaining a small distance from each other. The lesser horseshoes, as the name would suggest, are smaller than the greaters. The lessers can be a bit more elusive too, sometimes tucked away in crevices. We make our way around the caves, counting the bats in a systematic fashion.
In the main, the caves are quite open and spacious so you can walk around in them; there are only a couple of places where you need to crawl or lie down and wiggle through. We also record the temperature and relative humidity of the caves and the outside, plus the times of entry and exit. The January and February information is fed back to the National Hibernation Survey organised by the Bat Conservation Trust. In addition to this we send all of our survey data to the DBRC (Devon Biological Records Centre) and the local bat group.
Dave Ellacott, Reserves Warden, WWCT, with Dr Paul Chanin, University of Exeter and Chair of Trustees, WWCT and George Bemment, bat consultant