Steve,
Without getting too academic (we could discuss the literature off list?), I=
'd say the
evidence and general view for bats in Europe and North America is much less=
conservative
than your first sentence. For example co-occuring species in the genus Lasi=
urus (hoaries,
red and yellow bats, others in the American southeast) overlap in frequenc=
y to a degree,
but most are generally viewed as distinguishable.
While there are certainly Myotis that currently aren't separable acoustical=
ly in both areas,
there are others that are. Long eared Myotis calls in western NAm appear =
different from
the short-eared generalist species even to a neophyte observer. It can be w=
orthwhile to
think of comparing call 2D representations of call repertoires as being lik=
e the Venn
diagrams used in classrooms. Varying degrees of overlap determine how diffi=
cult it is to
differentiate two species. The very real challenge is learning where the b=
oundaries of each
lie.
There are useful differences in the calls made by confined bats. As an extr=
eme example,
several Old World families have "hardwired" echolocation calls that don't =
differ
substantially whether the bat is in hand, flying in a small space, or flyin=
g in natural
habitat.
On another axis, there several studies showing with small pools of individu=
als in a
laboratory that individual bats can be distinguished by calls (by both the =
experimenter and
the other bats).
Bill R.
> To my knowledge, no one has ever made a convincing case that bats
> could be identified to species (within a genus, say, like Myotis)
> based on echolocation sounds. Distinguishing genera (in eastern US at
> least!)is usually fairly easy based on frequency range and general
> pattern of sounds. Of course the tropical fauna is much much more
> diverse and less well studied.
>
> There's certainly lots of interest in doing this (identification)
> since many bats are endangered (way too many) and so there's demand
> for methods to survey for presence of endangered species more
> efficiently than trapping them and identifying them in hand.
>
> Bats make a lot of other sounds besides echolocation sounds that have
> received much less attention (because they're made within and near
> roosts for example and so not useful for surveys).
>
> I a small study a while back I looked at distress calls of Little
> Brown and Indiana bats ('distress' while in a human's hand being
> removed from a net/trap) and found significant differences--- enough
> for something like 90% confidence in discrimination between the
> species. These calls weren't ultrasonic but rather in the 4-18 kHz
> range or so with harmonics into higher frequencies.
>
> I'd be especially interested in learning about other's efforts at
> recording bat sounds within or near roosts or in hand. BUT NOTE that
> many bats are endangered and can suffer from disturbances, so such
> projects should be done very carefully and probably only with
> advice/supervision of experts.
>
> Cheers!
>
> Steve P
>
> --- In David Kuhn <dkuhn012001@>
> wrote:
> >
> > Hi Naturerecordingists, here is an mp3 of a bat I recorded in the
> Sierra at 8000 feet, Mkh 20 Mod SASS into SD 702. First 12 sec is as
> recorded, from 7 to 11 Khz; then the same sounds dropped in pitch to
> 700 to 1100 hz, using Audition's Pitch Bender. In spectral view I cut
> out all but the target sounds. I think it is quite a beautiful sound,
> with a lot of reverb, I had no idea. Is there an authoritative source
> for identifying bat species by their sound?
> >
> > Thanks,
> > David
> >
> >
> http://soundshawaiian.com/mp3/Sierra%20bat%20real%20and%20low%20pitch.mp3
> > or
> > http://tinyurl.com/5mvaf2
> >
> > =A0>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
> > David Kuhn
> > www.soundshawaiian.com
> > david@
> > dkuhn012001@
> > 808 335 0398
> > Cell 808 651 8247
> > Mail to: PO Box 1018
> > Waimea, Kaua'i HI 96796
> > <<<<<<<<<<<<<<<<<<<<<<<<<<<<<
> >
> > __________________________________________________
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>
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