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Let Sleeping Bats Be!


By Vince Simmonds

As the winter months draw in we may find that we have to share caves and mines with several other kinds of creatures, in cave entrances we may see cave spiders and possibly another species of spider, Nesticus cellulanus. Deeper into the caves common gnats and Herald moths may be found to hibernate along with other species of invertebrates (having no backbone such as insects etc.) and vertebrates (with a spinal column such as mammals etc.).  One of the most notable of these vertebrate species are Bats.

Out of the top ten species of British bats we could possibly come across eight species in caves or mines in the Southwest and Wales.  It should be noted that all species of Bat are fully protected by law under the Wildlife and Countryside Act 1981.  The conservation status of most bats is vulnerable and the Greater and Lesser Horseshoe are on the endangered species list.  We have already lost the largest of cave-roosting species, the Mouse-eared Bat (Myotis myotis) and some other species are close to extinction on the British Isles.  This is mainly the result of over-use of pesticides in agriculture and the subsequent loss of insect prey, however, we should do what we can to protect the species still remaining.

The Greater Horseshoe (Rhinolophus ferrumequinum) and Lesser Horseshoe (Rhinolophus hipposideros) can be recognized by their horseshoe shaped nose-leaf which are fleshy lobes around the nostrils.  They are distinguished from each other by size the Greater Horseshoe can be 55-75mm in length (excluding tail) and weigh up to 35g, the Lesser Horseshoe is around 35-45mm in length (excluding tail) and weighs between 3 and 9g.  These bats are likely to be present in caves and mines all year round moving deeper in during the winter where temperature is even and constant and it is frost-free.  They can be seen either as individuals which are usually older adults, or in groups which tend to be younger bats and can vary in number depending on conditions.

The Brown Long-eared Bat (Plecotus auritus) is immediately identified by, you've guessed, its long ears. It is 40-55mm in length (which doesn't include its tail) and can weigh about 15g.  They may also choose winter sites close to the cave entrance and have been found with a body temperature as low as 0oC.

Daubenton's Bat (Myotis daubentonii) is a smaller bat with rather large feet and velvety fur like a mole. Excluding its tail it is 45-55mm long and weighs up to 15g. Natterer's Bat (Myotis nattereri) has a fringe of short, stiff bristles along the edge of the tail membrane and they also have longish ears, 40-55mm long (excluding tail) and weigh 5-12g.

The Whiskered Bat (Myotis mystacinus) and Brandt's Bat (Myotis brandtii) are both small bats with dark skin and small ears.  They are not easily distinguished from one another although the Brandt's Bat may be redder in colour.  They are about 35-50mm in length, not including the tail, and weigh possibly up to 109.

The Serotine (Eptesicus serotinus) can be recognized by its large size possibly being 85mm long excluding its tail and weighing up to 35g.

Horseshoe Bats hang by their feet from projections on the roof and walls and wrap their wings tightly around the body like a cloak.  Most of the other species of cave bats will choose to crawl into narrow cracks and crevices and in amongst piles of rocks and boulders possibly for several metres because of this they may not be easily visible.

Try to avoid sites where bats are known to be hibernating and if you do happen to come across any bats make every effort not to disturb them, for example don't all stand around with lamps gawking at them.  Remember none of us likes to be rudely awakened from deep, drunken slumber at the Belfry.

Reference:

Cave Conservation Handbook; National Caving Association 9.4, Bats underground, 9-9

Caves and Cave Life; Philip Chapman (New Naturalist series)

British Caving, An introduction to speleology; Cave Research Group, x. Cave-dwelling bats, w.M. Hooper and J.H.D. Hooper pp 396-415

Complete British Wildlife; Paul Sterry (Collins)

Book of the British Countryside; AA

The Postcode Plants Database; The Natural History Museum