Posted by: "Rich Peet"
>
> For frogs I think you have to think a bit more like being a prey
> species. When there are multiple sounds from multiple directions you
> can not pick out the individual unless you are close. This makes it
> harder to become dinner because anything close other than another frog
> is identified as a danger and the frogs shut up. To illustrate this I
> walk up to a loud pond and clap my hands. All the frogs shut up. When
> one starts you can easily determine where in the sound field that frog
> is but once a bunch get going they all are difficult to locate.
There is more to it than that. The American Toad is the easiest to hear
one type of audio war for mates. By calling the same time as another
toad, but out of phase the toad will cause a beat that's ruins the
directionality. This is not to avoid being prey, but the one that can
call the longest, thus getting his location out at the end probably has
greater success at attracting females. American Toads have very long calls.
I'm sure other frogs are doing similar things.
Bird Voiced Treefrogs don't overlap their calls deliberately, but engage
in shouting matches. If you watch one it will listen to it's competition
and then aim it's call at the competition. They take turns trying to
shout each other down. BTW, Bird Voiced Treefrogs are not shy about
calling near a human, and they call at head height. They will call from
inches from your head and their call is very loud. The stun guns of
frogdom for humans.
Frogs have more than one call. Or sometimes the call serves multiple
purposes. The Coqui, for instance has a call that is at two frequencies,
one part is aimed at the female, and the other part is the territorial
claim. Males and females are each most sensitive to the appropriate
frequency for their part of the message.
Cope's gray treefrogs, in addition to their breeding call often give a
territorial squabbling call to warn off other males from their carefully
selected spot. Cope's grays select a calling spot for it's acoustics and
defend it.
Most, if not all male frogs have a "release call" which is given if
another male makes a error and grabs them thinking they are female. Easy
to demonstrate in toads, which not only call, but vibrate. I'm still
working on getting the release call of the little grass frog...
Most of the ranids here in Georgia have a "spit" call, which is a
territorial warning.
Green frogs have a location call, a announcement of where they are,
given most times of the year, it's not a breeding call, but might be
territorial to spread the frogs out.
Then there are the frogs who's mating call is not what you hear. They
call females seismically through the mud.
Note also that frogs are aggressive predators, not just prey. They are
ambush predators, as far as I know there are none that use sound to
attract their prey.
Walt
|