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Listening for Leisler's bat

With your detector tuned at 25kHz you should be able to detect Leisler's bat calls.

This species typically uses a two-part call often referred to as a ‘chip chop’ sound. Each pulse is fairly long compared to other bats and this gives it a very rich flavour. When flying high in the open it mainly emits lower "chop" calls (at around 23 kHz). When flying close to clutter it mainly emits higher "chip" calls (at around 27 kHz or higher).

These bats are big and fly fast but the repetition rate of the calls is slow, on average about 4-5 pulses per second, but sometimes even less as they fly high above the trees.

Play the sound on the right to hear a Leisler's bat heard through a heterodyne detector tuned to 25kHz.

The bat is flying high with its typical loud two part call - high and then low.

Similar species

On mainland Britain there is a similar species, the noctule. There have been possible records of this species in Ireland but these are unconfirmed. However, if you identify any bats that seem more like noctules than Leisler's bats then please record these as "Leisler's unsure" on your recording sheet.

Leisler's bat and noctule calls are best separated by tuning into the peak frequency of the lower "chop" calls which are typically around 23 kHz for Leisler's bats and 20 kHz for noctule bats.

When you are tuned to 25 kHz tune down towards 20 kHz and see if the sound gets deeper. Try to find the peak frequency – i.e. where the sound is at its deepest. If you find that the deepest frequency is below 22 kHz then record the bat as "Leisler's unsure" and make a note of the peak frequency.

In our analysis we will initially be lumping "Leisler's bat" and "Leisler's unsure" records together but if noctule is proved to be present in Ireland then making the above distinction will enable us to separate these records.

Identifying Typical Leisler's bat Calls:

• Call often has two parts and sounds like ‘chip-chop’ (but not always alternating).
• Repetition rate slow at 4-5/second (sometimes slower)
• Rhythm - regular punctuated with erratic bursts
• Tonal quality - deep, rich ‘chop’ sound & slightly higher ‘chip’
• Pitch/peak frequency – typically deepest at around 23 kHz (sometimes 22 kHz)

 

 

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If the sound gets deeper as you tune down to 20 kHz (as in the above clip) then record the bat as "Leisler's unsure". If the sound is deepest at around 22 kHz or higher then record the bat as "Leisler's bat".

 

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