Bill & Friends:
I agree with everything Bill's saying here and I certainly overstated
the situation earlier as my thoughts were (too) narrowly focused on
the difficulties of distinguishing certain "problem" species.
And, to add another example to Bill's, we have the sort of
funny/simple situation around Ohio that if you can hear it (unaided)
it's a Hoary!
Thanks for the much clearer and more accurate statement of the situation!
Steve P
--- In "werainey" <> wrote:
>
>
> 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 Lasiurus (hoaries,
> red and yellow bats, others in the American southeast) overlap in
frequency to a degree,
> but most are generally viewed as distinguishable.
>
> While there are certainly Myotis that currently aren't separable
acoustically 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 worthwhile to
> think of comparing call 2D representations of call repertoires as
being like the Venn
> diagrams used in classrooms. Varying degrees of overlap determine
how difficult it is to
> differentiate two species. The very real challenge is learning
where the boundaries of each
> lie.
>
> There are useful differences in the calls made by confined bats. As
an extreme 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 flying in natural
> habitat.
>
> On another axis, there several studies showing with small pools of
individuals in a
> laboratory that individual bats can be distinguished by calls (by
both the experimenter and
> the other bats).
>
> Bill R.
>
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