Friday, 15 February 2013

After dark ...

Bats in the attic?

Despite the loss of over 90% of our bats in the past 50 years or so, 18 species of these increasingly uncommon nocturnal creatures can sometimes still be found in southern Britain. Although legally protected, most species of these tiny intelligent mammals sadly continue to decline in numbers, mainly due to loss of habitat and changes in farming practice. All British bats eat only insects, populations of which have also reduced massively in the past fifty years or so. In Britain, a female bat has only a single baby (pup) each year, and often cannot give birth in poor summers; such as those we have experienced recently. Such slow reproduction makes it extremely difficult to reverse the decline of these beautiful and delicate mammals.

Most of our bats like to roost in trees, but a few species have adapted to take advantage of the opportunities offered by buildings at certain times of year. For example, a warmer environment can help a bat rear its pup during the summer. The pup is reared on its mother’s milk until it can fly, which may be as soon as three weeks after it is born. By autumn, the house dwelling maternity colony will typically be dispersing to mate and then to hibernate, perhaps in trees or underground sites.

Although they occasionally do, their presence needn’t worry householders – in fact most people remain quite unaware of their secretive little lodgers. Bats by their very nature are clean, gentle little animals, which spend much of their time grooming. They don’t build nests, so won’t bring any messy materials into the house and, perhaps most important of all, they don’t gnaw and chew at things, so won’t cause damage to electrical wiring and cables.

Bat droppings are sometimes found beneath roosts, but these are quite harmless and are not known to harbour disease. Droppings are sometimes seen on outside walls and windowsills near to roost entrances, but can also accumulate in lofts. If swept up after the bats have left, they make excellent fertiliser for houseplants. Bat and mouse droppings look very similar, but there is an easy way to tell them apart. Bat droppings consist only of the dried out fragments of insects and, if rolled between your finger and thumb, they will crumble away into dust; they also have a slight ‘sparkle’ about them. On the other hand, mouse droppings are solid, generally dull in appearance and remain in one piece.

Which bats live in houses?

The two very rare horseshoe bat species, the greater horseshoe (Rhinolophus ferrumequinum), and the lesser horseshoe (Rhinolophus hipposideros)like to roost in buildings, but are no longer regularly found in the south east of England. None have been recorded in Kent and Surrey for many years, and a mere handful remain in West Sussex. Usually found are our most common bats, the common pipistrelle (Pipistrellus pipistrellus) and the soprano pipistrelle (P. pygmaeus), which as crevice dwelling species, like to tuck themselves into gaps around the outside of properties rather than enter the loft space. They tend to do this mostly in the summer months when groups of females will cluster together in a warm spot to rear their young hidden beneath barge boards, hanging tiles and so on. In winter, odd individuals are sometimes found hibernating in similar gaps, but this time in the coldest rather than warmest places on the house. Perhaps surprisingly, pipistrelles seem very fond of modern houses, especially where small gaps and splits have opened for them into which they can squeeze. Though little more than an inch (2.5cms) in length, a pipistrelle can eat up to 3000 midges in a single night, and needs to do so to fuel its energetic lifestyle.

Another house specialist is the brown long-eared bat (Plecotus auritus), small groups of which will congregate in the lofts of (usually) older houses for a few months in the summer, again whilst the young are being reared. Larger than the tiny pipistrelle, it has huge ears, almost as long as its body, which it uses to listen by means of echolocation for its insect prey. The ears are tucked safely beneath the wings for protection whilst the animal is at rest. An individual bat will occasionally remain in a cold part of the loft to hibernate. A much rarer house dweller, and one of our largest bats, is the serotine (Eptesicus serotinus). Several times the size of a pipistrelle, it is still very small - a little over three inches (8cms) in length, although its wings may span over a foot (>30cms) in flight. These favour the lofts and attics of houses built at least 100 years ago where a few will occasionally roost during the maternity period. They have also been known to hibernate, usually singly, in roofs or cavity walls. Serotine bats are particularly fond of flying beetles such as cockchafers, which they catch on the wing. Other species of bat are much rarer in England and are very seldom found in houses.

Advice on your bats

If you have any concerns about bats in your property, do call the Bat Helpline on 0845 1300 228 – they can provide lots of advice and literature on bats, and even arrange free advice where building repairs, timber treatment and so on are necessary in or near a roost. Their web site provides a wealth of information about bats, and many leaflets can be freely downloaded. They also run a rescue service – so if you find a grounded bat, give them a call and someone will be able to help.

Bats and rabies

The European strain of rabies found in bats is extremely rare in Britain. Only ten cases have been identified since 1986, all of them in a single species that does not roost in houses. There is no need to worry about rabies if you do not handle bats – the disease is only passed via a bite or scratch, or from an animal’s saliva coming into contact with eyes, mouth, nose or an open wound. As a precaution, bats should not be handled. If it is necessary to do so in the case of a grounded or injured bat, gloves should be worn - and don’t forget to call the Bat Helpline, as detailed above, for advice or support from a local bat worker.

My thanks to Martyn Phillis (Surrey Bat Group) for his assistance with this article. All images copyright Martyn Phillis.

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