In a horror flick the bat is that fang-toothed flying rat that gets tangled in your hair while you run for your life. While they may send shivers down some spines, bats are in reality clean, gentle, intelligent creatures, as well as being absolutely fascinating to watch.
There are 18 species of bat resident in Britain. Of these 18 we have the three tiny pipistrelle species – the common pipistrelle, the soprano pipistrelle and Nathusius’ pipistrelle. While the common and soprano are frequently sighted and are two of our commonest bats, it is the Nathusius’ that has proved most elusive since it was first recorded on Britain's shores in 1940. However, the Canal & River Trust are installing several bat boxes and monitoring equipment around reservoirs in South Birmingham and Staffordshire in the coming months in the hope of spotting more, as well as planning some exciting bat walks this summer.
Words: Abigail Whyte
You'll often find Nathusius’ pipistrelle roosting near large bodies of water and river corridors along which they migrate and feed; usually in wall cavities, rock fissures, tree holes and hollows. Water attracts lots of insects, making it a prime feeding ground.
This bat is both a resident and migratory bat capable of flying vast distances. Part of the population migrates to the UK for winter from as far away as Scandinavia and Eastern Europe. There have been recorded sightings widespread across the British Isles.
During the breeding season and after the young are weaned in July and August, males sing continually during the night from their roosting site to attract a female. In late spring, females gather at maternity sites to give birth, usually in late May to early June. The baby bat or 'pup' is born blind and naked, feeding solely on its mother's milk for three to four weeks. It's able to fly at four weeks, then forage for itself at six weeks.
The Nathusius’ is larger than the common and soprano pipistrelle; measuring approximately 5cm in length – about the size of a human thumb. It weighs about 10g; the weight of a 50 pence piece. Average lifespan is two and a half to three years.
They generally have longer, shaggier fur than the common pipistrelle, with a reddish-brown colour and a paler underfur.
Soft, elastic skin stretched tight over arm, hand, leg and tail bones and elongated joints – the wings are, of course, all bats' distinguishing feature that equips them to be the only mammal that can fly. During flight, its wings are never flat – they're constantly adjusting their shape exploiting tiny fluctuations in the air around them, making them a true flyer, rather than a glider. A Nathusius’ pipistrelle's wings are broader than a common and soprano pipistrelle's, with a longer forearm and fifth finger.
The Nathusius’ has a high and jerky flight slightly faster than the common and soprano. Like all bats its aerial agility is incredible; catching its insect prey on the wing, also called aerial hawking.
To communicate, bats emit high-pitched sounds and listen to the echo for detailed information about their prey – its size, shape and location. The Nathusius’ produces a sound similar to other pipistrelles but its call is typically below 40Khz whereas the common pipistrelle call is around 45Khz. Their social calls, which are a lower frequency than their foraging calls, can be heard by the human ear.
The Nathusius’ has a voracious appetite, consuming thousands of insects a night – about a third of its body weight. It eats mosquitos, caddisflies and midges.
When to spot them
They can seen throughout most of the year if the evening is mild, but the best chance of spotting one is autumn when they concentrate on building up fat reserves to see them through winter, so they'll be out feeding regularly. Spring is also a good time when they feast on insects after winter hibernation. Keep your eyes peeled at dusk, when they're emerging from their roosts to feed. And don't forget to come along on a bat walk organised by the Trust – keep an eye out on the Trust's events page.
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