Bats

There are 16 species of bat in the UK. They are flying mammals. Some are very small – Pipistrelles could fit in a matchbox and only weigh 4g. This is quite amazing considering they can devour 3,000 insects in one night. Bats’ fur is quite long which makes them look bulkier than they actually are. They look after their fur and keep it clean whilst hanging by one foot and using the other claw as a comb. They moult and regenerate their fur every year.

Bats’ wings have a bone structure within them that are very like a person’s hand. It takes a lot of energy for a bat to start flying so they usually launch themselves off from a certain height, gain a bit of speed during the fall and hope to catch the breeze before they are flying properly.

At rest bats hang upside down as the toes and claws clench a rafter or even an apparently smooth surface. The weight of the bat keeps the toes in a clenched position. They can also grip with the tiny claws on their thumbs. Bats in a cluster hang on to the one above. Usually there’s many bats of the same species in a roost, sometimes hundreds. Roosting sites and hibernation sites are often different as the bats need different conditions at different times.

Echolocation

They rely on echolocation to help guide them at night. This involves emitting a short, loud shout (either through the mouth or the nose) and listening to the echoes it produces from trees, walls, insects etc. This way they gauge where and how far away their prey is. Some have evolved with specially shaped noses or ears to help them emit and receive sounds. They are sensitive to a higher pitch than humans so we cannot hear the ‘calls’. They can be picked up on a bat-detector which converts them into a sound we can hear and also gives a reading of the frequency of the call. It is this frequency along with other characteristics (such as the type of sound – clonk, click, smack – the flight style, time of emergence and habitat) that allows the bat species to be identified. When an insect is detected the calls become faster and faster as the bat get closer to its prey and then becomes a buzz at the point of contact.

Autumn and Winter

In winter there is less opportunity to feed so the bats hibernate in a state of torpor. They lower their temperature to match that of the weather and slow-down the heart beat. In late summer they build up fat deposits to tide them over the winter months.

Mating occurs in autumn but fertilisation is delayed till Spring after the female has carried the male sperm all winter. Babies are born in June or July in maternity roosts made up of female bats only, possibly many hundreds. Usually only one baby is produced by each female.

Originally bats were cave and tree-dwelling animals but now some buildings are just as useful. However mature trees provide suitable roosting places: cracks and splits, woodpecker holes, hollows or ivy. Noctules rely on trees for roosting and rarer species such as Barbastelles and Bechsteins seem to prefer the edges of woodland. Pipistrelles often opt for houses.

All species of bat are found on the warm south coast, 9 or 10 species are in the Midlands, but the northern most tip of Scotland has only 2.

Range of the species

The range of the species is affected by the climate but also by the availability of insects (all UK bats are insectivorous) which is affected by farming methods and woodland management techniques and the availability of roosting sites such as caves or holes in trees. Such reasons explain in part why some bats are rare, some thinly or patchily spread, and why others are widespread. For example, Pipistrelles are found in most areas of Britain and primarily roost in houses. Others, like Bechstein’s, roost in holes and crevices in trees often deep in woodland and suitable places are becoming more difficult to find.

All UK bats and their roosts are protected by law under the Wildlife and Countryside Act 1981 through inclusion on Schedule 5. They are also included in Schedule 2 of the Conservation (Natural Habitats &c.) Regulations 1994 (issued under the European Communities Act 1972).

It is an offence to:

• Deliberately capture, injure or kill a bat
• Intentionally or recklessly disturb a bat in its roost or deliberately disturb a group of bats
• Damage or destroy a bat roosting place (even if bats are not occupying the roost at the time)
• Possess or advertise / sell / exchange a bat (dead or alive) or any part of a bat
• Intentionally or recklessly obstruct access to a bat roost

Artificial roosting boxes

Artificial roosting boxes for bats can be used to try to encourage them to an area. These are similar to birdboxes but with a slot at the bottom rather than a hole in the front. Recently Countrycare erected a bat box at Bobbingworth Nature Reserve. Surveys had shown that the hedgeline was being used by bats for foraging so the box was erected to encourage roosting bats.