> Once in a while when recordings Anurans at night here in Texas, I will record
> a high pitched downward slurring call that is clearly not an amphibian.
Chris,
I'm on the wrong continent but I would suspect a shrew. I've picked up all
sorts of small mammal calls on bat detectors as well as on audio recordings,
but apart from "small mammals" not much further in the way of identifying
species.
However I have rescued shrews from cats and they can be very vocal with a
similar type of call. Rodents tend to have a coarser call, like bat social
calls and I would very much doubt a bat, even a bat social call, and it is
not like any echolocation call I know. These are usually a fast downward
frequency modulated sweep - FM - , or a constant frequency call, or a
combination "hockey stick" call with FM ending in CF.
How did you lower the frequency? If you did a linear heterodyne downshift,
this would exaggerate the "slurring" FM element pitch-wise.
David Brinicombe
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