A small tragedy

I found the dead bat on the path just outside the house this morning. It's a rare sight although they do live in the outbuildings and dart around in the twilight. They catch insects in the air but they also glean them from foliage and even the ground which is where they may be snagged by quick-witted cats.

Folded up it was hardly bigger than a mouse but with wings extended it measured around 20 centimetres. It's a common brown long-eared bat Plecotus auritus and indeed its ears are the most conspicuous thing about it, being almost as long as its body. At rest they are neatly folded away. The small projection in front of the main ear is called the tragus and appears to assist with echo-location, the means by which the bat navigates to such a consummate degree, dodging and swerving in and out of trees and buildings as it hunts. (For us our relatively inconspicuous tragus is mainly used as a handy attachment point for piercings.)

Echo-location, which employs sound waves bouncing off surfaces, is used by dolphins, whales and cave-dwelling birds in direction-finding where vision is limited. The ability that has evolved over millions of years and has resulted in a different sort of brain software from that needed for sight. Remarkably though, it's not impossible for humans to develop, or hone, the same power. A man called Daniel Kish, who has been blind since the age of one, discovered as a child that he could find his way around by clicking (he even learnt to ride a bike!) and he's devoted his life to teaching other sightless people how to do it. You can read about him here.

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