Possible Serotine at Eccleston Mere

Over the past few nights I've taken a more sophisticated bat detector to the mere in order to try to record some of the bat echolocation calls. Once recorded, I can then download the data onto my computer and analyse it in software packages such as Kaleidoscope View Pro and AnalookW.

Below are a couple of sonograms produced by AnalookW based on a small part of the recordings I made on Friday evening. The two Pipistrelle species, Soprano and Common, are relatively straight forward to identify, broadcasting at 56khz and 45 khz respectively. Noctule is also quite easy (at least in this area) broadcasting on 20khz and making quite a distinct slapping sound on the bat detector.

More difficult are the Daubenton's, which belong to a group of bats know as myotis bats, which have very similar echolocation. This group also includes Natterer's and Whiskered Bats, which are possible in our area. In the case of myotis bats, other factors need to be taken into account to confidently identify them, and in this case I am confident that they are Daubenton's due to the way in which they feed low over the water, at times almost picking insects off the water.

A fifth species was possibly recorded on Friday, the much rarer Serotine bat. This is a large bat, not too disimilar to Noctule, with a frequency of about 25khz. Serotine is largely a southern species, though there are a few records from the midlands and into the North West, with one record on the NBN Gateway from Clock Face. Kaleidoscope immediately identified this species as being present, but I'm not sure about the degree of certainty. However, I've compared the sonogram with known Serotine sonograms and the results do look good for that species. I've also shown the sonograms to a couple of more experienced bat experts who seem reasonably satisfied with the identification. I'd be very interested to hear from anybody who has more experience of Serotine to get their opinion. It's all a process of learning after all.

Other bats which may be present at the mere include Brown long-eared Bat which has evolved a very quiet echolocation (hence the big ears!) so that moths can't hear it approaching. This means that it's quite difficult to pick up on bat detectors and at such a busy bat site as Eccleston Mere it gets drowned out by the louder species.

A fascinating subject!


This sonogram shows Soprano Pipistrelle at around 56khz and Noctule at around 20khz. There may also be Common Pipistrelle on the sonogram, at 45 khz.


This is the Serotine sonogram (25khz) which also has Noctule and Common Pipistrelle. Their are lots of bats at Eccleston Mere, all flying around each other and in all directions, and their calls get mixed up. In the center of this sonogram, you can see that the call drops to a little below 25khz, which could be the Serotine going lower, or it could be the Noctule going to a higher frequency. At busy sites this is one of the problems with identifying bats from their echolocation. Bats do change frequency a little depending on what they are doing, and as they get closer to prey.

I'm still very much learning about bats and their echolocation, so if anybody has any comments about my identification, or any other aspect of bat echolocation please let me know.