The greater horseshoe bat

The greater horseshoe is one of our rarest mammals with a total British population of about 5,000 mostly found in the south west of England and Wales. It is also a very specialised creature with many unusual habits.

There are two species of ‘horseshoe’ bats found in the UK, the lesser and greater. They differ from each other in size but as a pair they differ from other bats in the way they emit their echo-location sounds. Most bats make their high-pitched echo-locating calls through their mouths but horseshoe bats make them through their nostrils. Look closely at a horseshoe bat and you will see that it has an unusual horseshoe-shaped nose. This directs the sounds, emanating from the bat’s nostrils, into a beam, a bit like a torch reflector directs light into a beam. In turn this means that the horseshoe bats have better ability to detect things in front of them but less ability to detect things to their sides.

The ears of a horseshoe bat are relatively large and can be twisted independently of each other enabling it to gather more information about directions and distances. Their wings are quite broad compared to other species of bat; this affords them better manoeuvrability but means that they can’t fly as fast. Their relatively large size means that it is more economical to make short flights from a perch than to fly constantly in search of prey.

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Horseshoe bat's diet

The greater horseshoe bat’s diet varies through the year. In early summer lots of large beetles, such as cockchafers, are taken; later in summer more moths are eaten and then in early autumn, like many bats, one of the main targets of their attention is the crane fly. One prey item which has been found to be very important to the greater horseshoe bat is the humble dung beetle. A cow pat can incubate up to 100 dung beetle larvae and this can provide a significant input to the bat’s diet, as well as that of their young which are born in June or July.

The dependence of the greater horseshoe bat on this source of food has also led to some cause for concern. It has been found that where farmers use certain types of chemicals to worm their cattle the dung is sterile and dung beetles are absent. Strategies which can be employed to address this issue include using other chemicals and employing better animal husbandry in which cattle are rotated between pastures. It should be said, though, that farming is essential to the survival of this species of bat, without grazing its existence here would soon come to an end.

Habitat and breeding

Conditions in south western Britain are best for greater horseshoes for several reasons: there is a mild, damp climate which is good for the insects on which it feeds; the field systems are small with good hedgerows along which the bats can feed; there tends to be a good mix of farm types including plenty of cattle, sheep and arable often close together and there are plenty of sites in which the bats can roost including old churches, deserted out-buildings and, particularly in Cornwall, mine shafts.

The annual cycle of life for a greater horseshoe bat starts with hibernation through the winter. These winter roosts can be in old buildings, cellars, tunnels, caves or even mine shafts. During the summer males and females split into two different roosts, the males form what are known as bachelor roosts whilst the females enter maternity roosts to give birth to their single young for the year. This young bat can be held under the mother’s wing when first born and the mother has a special nipple which the young bat can hold on to even in flight but generally the young bat is left in the roost whilst the mother goes out hunting, she returns regularly to feed it with her milk.

At about five weeks old the young bats are old enough to hunt for themselves, though they continue to receive some of their mother’s milk for a while yet. In early autumn the bats gather together in a communal roost and this is when mating takes place. The bats then hibernate for the winter. The lifespan of a greater horseshoe can be up to 30 years and they can breed until they are about 20 years old, so although they don’t raise as many young each year as most other small mammals they do have much greater longevity. Since these bats have at least four different roosting sites through the year it isn’t impossible that, at some point during the year, they might be roosting somewhere near you, or even in your attic. Horseshoe bats are easily distinguished from other bats because they hang upside down. Have a look in your attic, cellar and any outbuildings during the daytime throughout the year and if you find any signs report them to your county Wildlife Trust.

Comparison with lesser horseshoe bat

The lesser horseshoe bat is similar in shape to the greater horseshoe but smaller in size, it has a wingspan of between 200 and 250mm compared to between 300 and 350mm in the greater horseshoe bat. It is more numerous than the greater horseshoe with a UK population of about 50,000, about half of which are found in Wales.

Protection

All British bats are protected and it is an offence to disturb them.

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