The secret world of bats Print E-mail
Written by Frances Hancock, 2005   

Have you ever seen bats late on a summer's evening, silently flitting round trees and hedges as they hunt for food? Roosting by day and venturing out at dusk to hunt for insects, they are difficult to see. 

They are so small that each weigh less than a £1 coin. They have fur and give birth to live babies and are the only true flying mammals. Perhaps because of their shadowy presence and nocturnal habits, bats came to be associated with witches and magic spells in the past. In fact, even today some people are still afraid of them, believing them to be somehow harmful.

Others fear they can get entangled in your hair, a myth that is quite unfounded, since they are guided by their own ultra-sonic system. As for vampire bats that drink human blood, that really is fiction! These live in Central and South America and feed mostly on cattle and poultry.

There are over 1,000 species of bats in the world and the commonest bats in the UK are the pipistrelles. They are about 4cm (1 1⁄2 in) long yet able to consume up to 3,000 insects in a night - one-third of their body weight. Around canals and rivers there are likely to be Daubenton's bats, sometimes known as water bats.

These are slightly larger than the pipistrelles and fly low along the water, searching for cadis fly larvae and other insects. They are particularly agile, twisting and turning in the air like acrobats and, like the other insect-eaters, getting their tremendous energy from their protein-rich diet.

During the winter months when there are few insects, bats hibernate. Their body temperature drops and their breathing slows down so as to use up as little of their fat reserve as possible. Some of them cluster in groups (roosts) where they need to be left undisturbed. If there is a mild spell they may become active for a short time to look for food.

'Fingers' for flying

Bats' wings are quite unlike those of birds. They are like elongated fingers with membrane stretched over them from the shoulders to the toes. The 'thumbs' are actually claws for clinging to rough surfaces so that the bats can hang upside down when resting.

Everyone knows that owls have large eyes that are adapted to seeing in the dark. Bats have tiny eyes (they are not blind), but have little need for excellent sight since they depend almost entirely on their sensitive ears. They can however see as well as humans in daylight. They also have highly-adapted sense organs in the delicate wing membranes and in the whiskers around the muzzles.

Bats navigate by emitting short bursts of high-pitched sound and listening for the echoes. This gives them a sound 'picture' of their territory and enables them to avoid obstacles and catch insects in flight. Different species emit very different calls, but they are so high-pitched that humans cannot hear them.

It is possible to buy bat detectors that change the bats' squeaks into noises audible to humans and with practice each species can be identified. Development in radio tagging has brought more understanding of the extent of the bats' foraging habits. Some animals travel over a ten-mile radius or more every night.

In the nursery

All through the winter the female bat carries a fertilised egg within her body until spring, when the embryo starts to develop. The pregnant mothers all gather in nursery roosts where each will bear one baby in June or July. The young are blind and have no fur, but being fed on mother's milk they grow very quickly and are soon ready to forage for their own insects. There are no nests, so babies cling to their mothers as they hang upside down.

It is very difficult to count bats as they sometimes roost in inaccessible places and often move around to different sites. One thing is certain, though, the number of bats is declining. The Wildlife and Countryside Act 1981 first gave bats protection in the UK, and in 1990 the Bat Conservation Trust (BCT) was formed to provide a national voice for bats. A licence is required to handle bats, and fines for interfering with any roost sites or blocking their entrance can be severe, though unfortunately these are limited in their effect.

Building conversions and the dramatic increase in the number of new houses being built has had a severe impact on the bat population, while more concrete roads, traffic noise, bright lights, tree felling and pollution all interfere with their life cycle.

Home-owners and builders who neglect to check may not even realise bats have taken up residence until renovation has begun and the roost has been disturbed. Only rarely are bats actually seen in the roof space because most species crawl into tiny crevices, but if you see the tell-tale crumbly, mouse-like droppings tell your local bat group and give them the opportunity to visit and confirm the identification.

"Bats spend a lot of time grooming themselves and each other, so they are very clean animals," says the BCT.

"We find that when householders realise how harmless bats are, most are happy to have these fascinating animals roosting in their roof and thus play a vital role in bat conservation."

Bat-friendly gardens

You can also help these shy little creatures by creating a bat-friendly garden. Night-scented flowers will attract more moths and other insects, and water in any form is an attraction. The experience of bat carers suggests that domestic cats are the biggest predators of bats in the UK, so try to keep your cats indoors at dusk and dawn during the summer months to reduce casualties.

Organic farms are known to have more insect life that encourages bats to forage and therefore help to reverse their decline. If you can emulate them by giving up chemical insect sprays for pet-friendly powders available from the garden centre, then bats will benefit.

Any tree holes and rough walling will provide roost sites but design details are available for making bat boxes. These are like bird boxes but have a small slit at the bottom. The wood must be left untreated. You can also buy ready-made bat boxes.

Bats are very busy in September when they are building up a store of fat ready for the winter. This is the time when mating takes place and they begin to look for suitable sites for hibernation. Unless the weather is particularly mild they will begin to hibernate in October, collecting in groups of various sizes.

If you are lucky enough to be able to watch bats flitting around your garden on a summer's evening it's a sign that your local environment is healthy - bats are an important part of our biodiversity. To become more involved in local bat conservation, consider joining your local bat group. Most groups run bat walks in public parks and open spaces, forming an ideal introduction to the mysterious nocturnal world of this fascinating creature.
 
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