Volume 35 Number 1 Article 6
Follow That Bat
From time to time we encounter bats underground. We usually meet them singly hanging upside down in some quiet comer of a cave, and we wonder for a while how they got there, are they alone, what species are they?
In the past Red Rose members have observed and recorded the presence of these little understood mammals. The purpose of this short article is to focus club members' attention on bats, and explain the real contribution we as cavers, can make to the recording and understanding of bats.
There are fourteen species of bats in Britain, but we won't find all these species in the North of England. The trouble with most caving textbooks which have chapters on bats is that they concentrate on the numerous bats to be found in places like Mendip, mainly the horseshoe bats; and we just don't have horseshoe bats in the North. The species we are most likely to meet in the caves near Bull Pot Farm are Natterer's bat, Daubenton's bat and brown long-eared bat. Whiskered bats and pipistrelles live in the area, but we don't usually meet them in caves.
Identification of bats is not easy even for the experts. The ultrasonic echo-location sounds they emit in flight can be picked up by a bat detector; an instrument which converts the sounds to frequencies audible to humans. The pattern and frequency of the sounds help to identify the species of bat. However we don't normally carry a bat detector with us underground. Bats are protected under the 1981 Wildlife and Countryside Act and it is illegal to disturb them. Only people with a special licence are allowed to handle bats, except under special circumstances in the bat's own interest, such as picking up an injured bat to take it to the vet. It's also illegal to disturb hibernating bats by taking flash photographs of them (sorry Ray). Some species are so similar that they can only be distinguished, in the case of Whiskered and Brandt's bats, by the shape of the male penis - a bit tricky to study this in flight.
So, if identification is in fact so difficult what useful work can cavers do? The fact is that the number of bats nation-wide has dropped dramatically in the last 20 years. There are several suggested reasons for this. Bats feed exclusively on insects in this country. Modem pesticides have resulted in a decline in the insect population. Loss and disturbance of habitat is another factor: Hopefully, this won't happen down caves. So, any record of the presence of bats is useful information. It is not that often that we see the bats themselves underground, but much more frequently we come across evidence of their presence if only we can recognise it. You often come across an accumulation of debris from their feeding habit. The bats will fly around outside at dusk collecting insects then return to their roost, and hang upside down whilst they have their dinner. They don't like the hard part of the insects such as wing cases, wings and legs, these are discarded and accumulate on ledges etc. beneath. Not surprisingly, the heaps of debris also contain bat droppings. Superficially these look like mouse droppings, but you can tell the difference if you smudge one with your finger. Bat droppings being made of the indigestible parts of insects, are comparatively dry and crumbly whereas mouse droppings are, well, different. Try it and see. If you carefully collect some bat droppings and remove them from the cave, it can be quite good fun to look at them through a microscope and identify the body parts of the insects.
What we can do then is:
a) confirm the presence of bats, either by observing them directly, or noting the evidence of their presence.
b) if possible count the number of bats in a roost.
c) have a go at identifying which species. It may not be possible to say which species they are - we might be able to say which species they aren't. See poster at Bull Pot Farm. You may be able to note the size, colour of the face, do its ears meet in the middle? Has it got big feet? Remember to record the date as well as the location.
This is all very good of us making our contribution to saving wildlife but what's in it for us? Apart from the obvious that bat watching is something you can still do underground when you're too old and creaky to bottom the big ones, the pattern that's emerging from observations so far is that bats are usually found not that far into caves, usually just beyond the daylight zone, far enough in to avoid the extremes of temperature. So If you find a bat a long way underground, after you've been thrashing along for several hours, maybe the bat knows something you don't. Follow that bat!
At the photo competition Ray showed a photo of a dark coloured bat hanging upside down in Link Pot. It seems that this was almost certainly a Serotine bat, a species rarely found in northern England, so it was a very good sighting. A few summers ago, old Red Rose member Pauline Barber and the Northern Bat Group recorded a dozen Serotines down Link, so this site is well worth watching.