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Bat Sounds

As dusk advances you may be lucky enough to see bats, but as darkness falls you usually don't even know they are there.

Drawing of Natterer's BatThis image is of two Brown Long-eared Bats flying with a few others under the eaves at the front of our house in August 2005. On another occasion we recorded their soft call - nothing like the powerful calls on the rest of this page (will add at a later date).

There are lots of silly ideas about bats - like them getting tangled in your hair in the dark. This just doesn't happen - they are wonderful navigators in the dark, and manage this not with super-sensitive eyes (like owls) but by echo location - seeing by sound. Unlike birds, they do not fly into window glass because it is opaque in their sound world.

Basically they emit a 'chirp', and listen to the echoes. (Usually it is described as a 'click', but the slowed down recordings will persuade you that it is a sliding tone.)
From these echoes bats can build a rich 'picture' of the world about them. However impossible this seems, dolphins obviously share the skill. Try to explain vision to a person who has never had sight, and the difficulties of understanding a completely alien form of perception become clear.

But you hear dolphins calls, but you can't hear bats. Why not?
Humans can only hear sound up to about 16KHz (that's 16,000 cycles per second). Bats emit sounds at typically 2 or 3 times higher pitch than we can hear. Sounds above human hearing are usually called ultrasonic.
Whales and elephants can make sounds below what we can hear, about 16Hz (16 cycles per second), and these are called infrasonic.

So how can we make sound files for you to play?

The answer is the Bat Detector, an electronic box that has an special ultrasonic microphone (ordinary microphones only just manage the human range of sound) and electronics to make the sound audible. The recordings below were all made on warm evenings at dusk in April 1998.

In the bat detector we have there are two ways to make the sound audible:-

Some people think bats are ugly or grotesque. Look at those facial features with the eye of an amazingly designed audio transmitter and analyser that can paint a picture of the world, and maybe your view will subtly alter.

In the UK bats are heavily protected species in decline through loss of both natural roosting habitat such as undisturbed caves, and changes in housing design that make loft spaces unsuitable or inaccessible. If these calls from the dark make you feel that bats have a place in the world, then they were worth making!