Both species are audible at the start of this recording. At the same time that the Green Treefrog joins in,
the Southern Cricket Frogs become quieter and the Northern Cricket Frogs are more distinct. On a CASP route, the listener might not get closer than I was when I made this recording, so it is necessary to distinguish between the two species at this range. This is just close enough to hear the clicks of individual frogs.
Clicks are made up of “pulses” and the two species sound different because their pulse patterns are different. Southern Cricket Frogs have short pulses that are repeated quickly and regularly and become quieter
at the end of the click. Northern Cricket Frogs have longer pulses that are repeated
more slowly and irregularly and do not become quiet.
Southern Cricket Frog clicks Northern Cricket Frog clicks
sound like: