At 7:51 PM -0500 12/16/08, Marc Myers wrote:
>Anyone have experience locating animals by measuring distance and
>direction of their calls in natural environments? Gibbons often live
>in difficult terrain, at low densities and in small family groups.
>They can be hard to see in their native environment and are
>critically endangered through the majority of their range. Making
>population estimates is important in conservation planning, when
>advising local governments on forestry use and establishing risks to
>extinction. Gibbons have famously loud and expressive calls,
>typically sounded first thing in the morning. Populations are
>presently estimated based on the frequency, direction and apparent
>distance of the calls. Of course even experienced listeners are not
>very good at estimating distance and as a consequence population
>estimates vary wildly from environment to environment and researcher
>to researcher. Any thoughts?
>
>
>_
Hi Marc--
Here's another "wild" scheme. If pinpointing where the calls/animals
are located is really important, one could record with 3 omni mics in
a large, equilateral triangle layout. I'm not sure what distances
between the mics to recommend but 500 feet or more would probably
provide enough accuracy to identify their favorite calling spots in
audible range with certainty, maybe even determine that animals are
on the move. You'd need to know the exact distances between the mics
and record all three tracks at once. Arrival time differences are
easier to measure (and hear) with percussive calls than sustained
ones and that might be an drawback with Gibbons. One could use
wireless transmitters (a hit, quality-wise) but an option if running
wire isn't possible. Rob D.
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