What Behaviour Does This Pipistrelle Recording Show? (1 Viewer)

[Psamathe]

Last night again recorded probably (Common?) Pipistrelle and as I often see some "pulses" I can't find anything about i.e. to my inexperienced knowledge, not navigation, not approach, not feeding buzz (but I've no knowledge about interactions between bat calls). These "pulses" seem longer duration than normal navigation and very low frequency.


I assume they are from the bat(s) (probably only the one) as they are mixed in with more recognisable calls and only happen when the mor erecognisable calls are ongoing


And one of the more recognisable calls (in case I've completely messed-up in my inexperience)


(Sorry if I'm missed out any critical info - do ask for details)

Many thanks
Ian

 

[pppppvvvv]

Hi. No idea I'm afraid.
You are quite right, you have the typical common Pipistrelle echolocation. The feeding buzzes are usually a similar frequency, but much faster.
Social calls are around 20khz (?)

Your other calls are really low frequency. I'd be tempted to say they aren't from the bat, but they do seem linked so I see where you are coming from.

Could be, and this is a wild guess, another species, (insect?) responding to the bat calls?
I know there is talk of Moths jamming the bat signals for their own defence.

Or, is it the audible output from your bat detector feeding back into bat detector microphone?! I say this as there is a definite gap between my detector processing a call, and it reaching my headphones.

 

[Psamathe]

Hi. No idea I'm afraid.
You are quite right, you have the typical common Pipistrelle echolocation. The feeding buzzes are usually a similar frequency, but much faster.
Social calls are around 20khz (?)

Your other calls are really low frequency. I'd be tempted to say they aren't from the bat, but they do seem linked so I see where you are coming from.

Could be, and this is a wild guess, another species, (insect?) responding to the bat calls?
I know there is talk of Moths jamming the bat signals for their own defence.

Or, is it the audible output from your bat detector feeding back into bat detector microphone?! I say this as there is a definite gap between my detector processing a call, and it reaching my headphones.

It was not a "one-off" but nor was it with every sequence recorded. I'll use headphones next session to eliminate the feedback possibility. I wondered about insects responding but (again without knowledge or experience) I thought it a bit rapid when any prey insects would be prioritising avoiding being caught.

I have spotted one where the "weird" bit merges with a recognisable pulse (with the start of the pulse)

Or in the middle


I've assumed (maybe incorrectly) that the "stacked spectra" in the above record are reflections as I was close to a couple of buildings.

It's what I regard as "lowish end" quality wise, an Wildlife Acoustics EchoMeter Touch for iOS (NOT the Pro version).

I was not far from low voltage (240V 3 phase) power lines and wondered about electrical interference but when the bat flies away, so does the weird signal.

Ian

 

[pppppvvvv]

Don't know. Maybe experiment with headphones etc. Or just have to ignore them. Luckily you are still getting good calls to identify with.

The last pic, I'd say was a Noctule, at ~20,khz, with harmonics echoing this at 40khz. Although if it is, it's very fast repetition.
I think I'm right in saying, if you have harmonics, then the lowest is the bat, but others may be able to give you better details.

Peter

 

[Psamathe]

Don't know. Maybe experiment with headphones etc. Or just have to ignore them. Luckily you are still getting good calls to identify with.

The last pic, I'd say was a Noctule, at ~20,khz, with harmonics echoing this at 40khz. Although if it is, it's very fast repetition.
I think I'm right in saying, if you have harmonics, then the lowest is the bat, but others may be able to give you better details.

Peter

I'm still at early stages of learning and to make learning harder the software "auto-detects" the species though mostly offers a choice of 2 (Common or Soprano Pipistrelle). Software also auto records detections and the recording I'm using for all above shots is 15 secs long. Time spent outside bat would appear (be heard) for a short time then disappear for several minutes then re-appear - so I'd (maybe incorrectly) guessed there was just the one bat flying round.

Same session using a much longer time axis (so spectra not so clear but the 29 KHz looks like 1st call and 47 KHz the 2nd. But the 1st call also has spectra lines bottoming at 47 K Hz - is this a characteristic of Noctules?


Looking more closely at the recordingabove zoomed in time range it's a repeating pattern:

I don't know if this is significant but the regular double navigation pulses bottom at 46 KHz.

If I do a detailed analysis of the left of the two sections with the lower frequency (just that small bit not the entire sequence:


Location is edge of tiny village (East Anglia) with farmland and hedges around most sides but within garden some good hedgerow and trees (some dead but still upright!).

(Sorry to be taking up such a lot of your time - but I'm learning loads; thanks).
Ian

 

[pppppvvvv]

If you can, select a call, and look at the spectrum, which will show you the peak power.
This will help identify in many cases, e.g. common pip at 45khz, soprano at 55khz.

many other species can be identified by this alone. E.g. nathusius pipistrelle 39khz, barbastelle, low 30s; serotone high 20s, Noctule ~20. Greater horseshoe 87khz, some of these are quite rare, horseshoe not found in your area.

try and record them in the open, as their calls change in clutter.

i think your last one is a common pip (peak at ~45khz hockey stick shaped, and the social calls at about 20khz.
Noctules are 18-24, much slower chip-chop sound.

What I thought was a Noctule, could be the common Pipistrelle social calls stretched out on the graph.

not sure where you would go to get more info / training, but post stuff on here if you get stuck. Good thing is there aren't many species to choose from!

 

[Psamathe]

...
not sure where you would go to get more info / training, but post stuff on here if you get stuck. Good thing is there aren't many species to choose from!

There is a book "British Bat Calls: A Guide to Species Identification" (Bat Biology and Conservation) on Amazon https://www.amazon.co.uk/dp/190780725X but at £35 (and 192 pages) I've not rushed. Kindle version is cheaper but travel guides I've had on Kindle the maps and diagrams displayed really badly (Kindle Paperwhite resolution and grey scales) and I'd hope the book has plenty of pictures and plots and diagrams.

For me learning is both with help from others (e.g. yourself) and suggestions that I can explore further myself. e.g. your suggestion about insect blocking bat calls directed me to research and it has been seen in some tiger months (2 species common in UK gardens) and less known about Hawk moths (and I used to have Privet Hawkmoth caterpillars) - but the frequencies of their blocking look higher than those weird ones on my plots - but it was only a brief look and I'll investigate further when I get a bit more time.

Ian