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October 30, 2010 12:32 am
Bats get a bad press. People find them ugly, creepy, scary. They suck your blood and give you rabies and tangle themselves in your hair, right? Well, no, actually. Bats, seen in the calm light of reason, are rather beautiful, highly specialised and delightful creatures – and great at hoovering up midges and other thundering nuisances. Sussex is a county rich in bats – in fact all 17 of the UK’s native species are resident, and 14 of these have been found on the Petworth Estate in the western region of the county. That way I headed, one drizzly evening.
A damp, cloudy evening, steamy with moisture and the threat of rain, is just the kind of evening not to be bat-watching. But our rendezvous at the gates of Petworth Park had been fixed many moons ago. Crispin Scott, the National Trust’s Regional Nature Conservation Adviser, was waiting with his young son Alf to take us for a walk on the wild side of the park, superbly landscaped in the mid-18th century by “Capability” Brown. “Bat detector,” Crispin said, handing over a stout black box knobbly with buttons. “I’ll show you how it works when we’re out in the park. But let’s have a look at the tunnels first.”
In the brick-lined tunnels that connect Petworth House with its servants’ quarters, thousands of bats of seven different species hibernate the winter months away – Brandt’s bats, grey and brown long-eared bats, Daubenton’s bats that hunt insects over water, common pipistrelles, whiskered bats and rare Bechstein’s bats. But on this late summer evening the eerie tunnels lay empty.
Out in the park the light was beginning to fade. The great house stood, shadowed by rain, in a man-made landscape of subtle curves and hollows. In front of us a spinney of oak and sweet chestnut perched artfully on a scenic knoll. “Clumps on lumps,” said Crispin, “very good for bats – the air’s still, there are plenty of insects, and it’s sheltered.”
Waiting among the trees for whatever the dusk might bring, Crispin brought us up to speed on the Petworth bats. No artificial fertilisers are used on the estate, encouraging insects, which in turn attract the bats. Each bat species has its own preferred habitats: barbastelles, for example, like lightly wooded places, Bechstein’s prefer heavy tree cover, while Daubenton’s need water over which to hunt insects. A common pipistrelle is only as long as one’s thumb, but can pack away 3,000 midges in one night. Noctules are bigger than the other bats – they can tackle a cockchafer.
Bats hunt and find their way by echo-location, emitting a stream of sounds too high-pitched for human ears and measuring the returning echoes as they bounce back off objects. The echo-location is so precise that the bat can identify an insect even if it’s sitting motionless on a leaf, and pick it neatly off as it zooms by. Each species transmits at a different frequency – soprano pipistrelles at about 55kHz, common pipistrelles at 45kHz, Daubenton’s generally at 45kHz-50kHz, noctules down at 25kHz. The bat detector reduces the transmission to a sound we can pick up – a crackle or quick vibration, which accelerates sharply to the “feeding buzz”, a wet squelch exactly like blowing a raspberry, when the bat closes in on an insect.
We were scarcely expecting much action on this damp evening, but as we waited in the clump on the lump, little black bullets suddenly started zipping round the glade. “Soprano pipistrelles,” whispered Crispin, “tune your detectors to 55kHz.” The pipistrelles streaked by in pairs, with the juveniles, learning to hunt, following their mothers in close formation like tiny fighter planes. Three or four bats soon became 20 or more, some of them flying within touching distance of us, crepitating and buzzing.
“I’ve never seen such a good display,” exclaimed Crispin, “and these are the worst conditions of any bat expedition I’ve done!”
Down by the lake there were noctules flying overhead, their echo-location translated by the bat detectors into a chop-chop-chop as of miniature helicopter blades. Daubenton’s bats hunted insects over the water, crackling like burning stubble as they darted with a flash of pale belly through the beam of Crispin’s torch. Natterer’s bats, on the wing after small moths, made bristly noises. There were quiet ploppings and quackings from out on the dark water to remind us that other denizens of the lake were about their nightly occasions.
Walking back through the park we saw the great house lost in the night. Of its scores of windows, two solitary squares shone as beacons of light and human presence. All around us the feeding frenzy of the pipistrelles continued unabated.
Christopher Somerville is the author of ‘Never Eat Shredded Wheat: The Geography We’ve Lost and How to Find it Again’ (Hodder & Stoughton)
Bat file: Where they can find you
Bats at Petworth
For details of guided Bat Walks, write to Petworth House and Park, West Sussex (NT), or telephone 01798 342207, or visit www.nationaltrust.org.uk
Further information: Petworth TIC, 01798 343523; www.visitsussex.org
Bats are most active for an hour or so around dawn/dusk. From late November to early March they hibernate. To watch bats, look for a place with still air, plenty of insects and shelter close by – on the edge of tree clumps and beside water are two good spots. Get in position by dusk, and keep quiet and still. A good bat detector (£60 upwards) is essential (see www.bats.org.uk).
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