The silence of the bat detector

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In a world before bat detectors, nobody realised just how many different species of bat there are. There is only one word to describe all of them in the Cornish language (according to The Mammals of Cornwall and the Isles of Scilly by Cornwall Mammal Group, edited by David Groves): askel grohen (leather wing). In fact, 13 different species have been found in Cornwall alone.  

When the mines were first capped, I bet no one thought to leave holes for bats to go in and out, and perhaps many were trapped inside and perished. These small mammals may now be a little better understood, but because of the way we are changing their environment and affecting their food supply, they are under great threat and protected by law.

Lesser horseshoe bat hanging from a branch
A lesser horseshoe bat hanging from a branch. They usually roost in old buildings. Drawing © Rowena Millar

By sealing up our buildings and felling old trees that might be dangerous, we are sealing out bats and taking away their homes. By lining our roads and adorning our properties with bright lights, by tidying and and sanitising our countryside, ridding it of its bogs, ditches, ponds, wild edges and hedges, meads and weeds, we are harming bats. In Cornwall, we are fortunate to have retained some old barns and ruined mines, old woodland, stone bridges over quiet rivers and sheltered valleys where bats can still find some food and shelter.

Drawing of a lesser horseshoe bat in flight
A lesser horseshoe bat in flight. Drawing © Rowena Millar

A while ago my husband gave me a small, simple bat detector. Every year up until then I had been spending happy summer evenings watching bats emerge from a tiny crack in the wall of a nearby older house in Kelly Bray, standing supposedly nonchalantly in different places around our garden and looking apparently vaguely out of different windows, so that I didn’t appear to be staring at the neighbours and their property!

A whole string of bats, numerous as little flags along tens of metres of bunting, flitted their chaotic-looking way, one after the other, down the gardens, out to a tall hedge and beyond into the countryside. Each one followed a different path, presumably distracted by insects or just delighted to be free of the claustrophobic furry bat-crush in their cramped little home. My curiosity was building as to which species these little flying mammals were.

On my detector I could hear excited twittering and ‘smacks’ as the creatures wriggled out of the crack, and took off joyously into warm, dusky summer evenings to go hunting on the wing. Most headed down into the valley, where a small stream with a slow-flowing section guaranteed the emergence of some juicy flying insects and a tangle of wildflowers offered their nectar to numerous moths. I think they were pipistrelles, one of the species you would expect to see and hear.

Some pipistrelles squeezed between layers of foam in a bat box, in Armstrong Wood Nature Reserve,
East Cornwall © Rowena Millar

For the last few summers I haven’t seen the colony of bats. I think we lost them after the house owner, who was selling his property, jet-sprayed the entire back of the house, including the bats’ entrance crack. When I noticed, I tried to catch his attention and shouted something out about the bats, but he said they’d be fine. The current occupiers have a very bright light on the back of the house, as do others in the village. Now I occasionally detect a single bat while waiting hopefully at the window while my little black box-shaped bat detector whooshes away but doesn’t warble, click or chatter very much, mostly recording only at a stray raindrop or if I’m lucky, a random cricket calling from the wall below.

Although … one evening during the summer of 2016, my detector made a strange, low swoopy sound and I saw something large gliding gracefully out of the dark, flapping steadily round the side of the house and out towards the streetlamp-lined road. Consulting my computer to identify the sound, I found out that it was definitely a greater horseshoe bat.

The face of a lesser horseshoe bat
The interesting face of a horseshoe bat. Note the horseshoe-shaped ‘noseleaf’ that may help focus sound. Drawing © Rowena Millar

Greater horseshoes – large and increasingly rare – have a wingspan of 40cm and a furry body about the size of a tablespoon, according to The Mammals of Cornwall and the Isles of Scilly. Like the lesser horseshoe bat, which is very small in comparison, they hang upside down in old chimneys or abandoned mines, wrapping their wings around them as they roost. So our sort of mild wooded landscape, here on the fringes of the Tamar Valley, is ideal for them (apart from all the brighter-than-bright new lighting, some insect-destroying overzealous hedge flailing, harmful chemicals such as pesticides on and inside our animals, and non-bat friendly building developments), and long may it remain so.

A hibernating bat. Drawing © Rowena Millar

Most of us will have seen bats on television on wildlife documentaries – often fruit bats, which are very much unrelated to the insectivores – flapping out of enormous caves in their countless thousands. This sort of scene will become rarer as we lose our unspoilt forest habitats around the world. How often these days do we see clouds of bats emerging from our barns, churches and homes? I suspect not as often as we would have done 10, 50, 100 or 200 years ago.

Armstrong's Wood view to River Inny
Good bat country © Rowena Millar

It would be so heartbreakingly sad if we lost our bat population, just at a time when we might lose our collective bat phobia. Surely these days it is a privilege to guide a stray bat out of a bedroom into the freedom of the night air outside, rather than a horror. But if you do leave a window open, how many insects come in and sit on your bedroom ceiling? The answer used to be “far too many to count” and now it is almost none. Is ‘almost no’ insects enough to support a healthy bat population?

To protect bats, we must avoid disturbing them where they roost, and allow insects to thrive. Bats need the insects that emerge from our ponds, damp meadows and heathland, hedges and woodlands and we must make sure that there are nooks and crannies, ponds and ditches, flowers, long grasses, flowers, shrubs and trees all around us (these things certainly make me feel happy and alive too).

Bat box, Kilminorth Woods
Bat box, Kilminorth Woods © Rowena Millar
Brown long-eared bats in wooden box 2007
Brown long-eared bats in a wooden box, Armstrong Wood Nature Reserve, 2007
© Rowena Millar

If we can bear bats in mind before we develop land, or modify our homes, then there is hope that my bat detector won’t fall completely silent forever.

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