Because gibbons typically call from the canopy and live in a 3-D
environment (as opposed to a plane), Rob, one would need to set up a
tetrahedral (pyramid w/ all mics equidistant from one another) in
order to approximate location. But because the rainforests where they
reside (Sumatra and Borneo in my experience) are so reverberant, one
would get complex arrival times at each mic obviating precise analysis
of location. To further complicate matters, the acoustics of these
biomes are in constant flux, changing rapidly with the slightest shift
in temperature or humidity or time of day. That said, if one has taken
careful measurements over time under different conditions, one might
be be able to approximate both distance and location assuming well-
calibrated gear that one can rely on under those conditions.
Bernie
On Dec 17, 2008, at 8:20 AM, Rob Danielson wrote:
> 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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