During 2017 we installed logging equipment at several abandoned mining sites in the project area to record the calls of bats.
Bats use high frequency calls, normally beyond the range of human hearing, to build up a sound picture of their surroundings.
Different species echolocate at different frequencies which can be used to identify the bat.
Our data has since been processed by the recently formed Cleveland Bat Group and the following species identified.
All photographs are taken from Wikipedia, no bats were captured or handled as part of this work.
A small bat that weighs between 4-7g with a wing span of 18-25cm. Pipistrelles emerge around sunset, and have an erratic flight – twisting and turning.
Echolocation calls are hockey stick shaped having peak frequency around 45Khz (circled in white)
Social calls between 15 and 40Khz (circled in black)
Feeding buzz is increasingly fast and higher frequency becoming more vertical then dropping with a gap before echolocation calls resume (circled in red)
A large bat that weighs 40g with a wingspan of between 33-45cm. Noctules emerge early in the evening, they can sometimes be seen flying in a straight line, high overhead.
Noctule calls are at a much lower frequency, slower and the calls often vary between a higher ‘chop’ and lower ‘chip’ averaging between 18Khz and 25Kz
This is a group includes Daubenton, Natterer’s, Whiskered Bat and Brandt’s Bat.
If you see a bat flying very low over water, skimming the surface, it’s probably a Daubenton’s bat. Weight: 7g – 12g and wingspan: 24cm – 27.5cm
The Myotis calls differ from Pipistrelle calls in that they are spread over a broad frequency range and are mostly straight.