Anyone know what's going on here?

[GregF]

These calls recorded south of Townsville, Qld.

Data set contains a lot of sequences like the two attached here; i.e. a set of quite flat pulses at <25kHz, interspersed with steep pulses at just below 30kHz.

I think it's two individual Mormopterus lumsdenae but am intrigued to know what they're doing. Any ideas? Anyone observed similar calls whilst making behavioural observations?

Cheers

GF 

[Stefan Nyman]

Hi,

interesting!

The low one looks like Mormopterus and the steep calls are similar to Mormopterus “active hunting” calls. But they are going on steadily and it doesn’t look like it is hunting really.

And it looks like they are together! The sound is fading the same way and you can hear (doppler effect) that they are disappearing at the same time.

 

Also waiting for somebody to explain this…

^ö^

Stefan

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[Chris Corben]

When you say you had a lot of sequences like these, can you elaborate a bit? Were there sequences of just one call type and not the other? Or were they always both? Do they all show this tendency to fade out mutually?

What are the recording conditions? Are these from a passive recorder? What was the surrounding habitat like? Was it windy? Was the recorder moving at all?

When I first saw these, my first thought was that the steep calls could be from a static bat, since they are remarkably uniform and also at a high repetition rate and steep calls for any bat at such low frequency. So a bat in a lot of clutter, yet making a very uniform sequence. But if the bat is static, then it is not so easy to see how it could be fading away like that, and much less so if it does it every time. And the Doppler shift, if that's what it is, would be hard to explain if the recorder was not moving.

A mother and child might be a possibility, with the child still being very incompetent!

Cheers, Chris.

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Chris Corben.

[GregF]

Hi everyone

It's happening again.  This time, data is from Mt Garnet in north Qld, recorded a couple of weeks ago.

Again, I'm seeing many sequences with these "duet" calls from Ozimops lumsdenae; one call with evenly spaced, very flat pulses and the other with steep, clutter-type pulses.

As suggested by Chris C. last year, it is possible that these calls represent a mother-young pair, perhaps in aerial training mode. Interestingly, this data set was recorded about a month earlier than last year's data.

Interested to know your thoughts on these.

Cheers

Greg F.