Again, it may be best to allocate one person to counting passes at the spots, and another to focus on identifying the species. It will help a lot if you can see the bats against a moonlight sky or street lamp.
Typical Pipistrelle Calls
Therefore, begin with the dial tuned to 50kHz but you will need to do a little more investigation in order to separate the species.
Pipistrelles use a series of calls at very irregular intervals. The calls have an average repetition rate of around 7-9 per second which is obviously much faster than Leisler's bat (and it can be even faster in certain situations).
These little bats are incredibly manoeuvrable in the air making twists and turns to catch their prey, and this is reflected in the erratic rhythm which has a kind of galloping quality.
Listen to this typical pipistrelle call. In this example the detector is tuned into the peak frequency and the call has a deep, rich, wet slap or popping sound.
Some people say it is like the sound made when slapping your thigh with a cupped hand (try it!).
here to play sound
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