Cope's Gray Treefrog
Hyla chrysoscelis

I found this Cope's Gray Treefrog (Hyla chrysoscelis) calling from some roadside branches after a heavy rain in Karnes County, Texas.

The call of this species is best described as a dry trill.  

This species is morphologically identical to Hyla versicolor, but they can be distinguished by call.  The call of H. chrysoscelis is faster, "drier" and much less "bird-like" than the call of its sister species Hyla versicolor.

Here is the recording of this individual Hyla chrysoscelis.  I have edited out some of the silent periods between calls.

And this is the sonogram for these calls:

The last sonogram examines a single trill of the preceding call.  
Each trill lasts approximately 0.5 seconds, although as with most frog calls, the speed of the call is correlated to the ambient temperature.

Here's a short video of a Hyla chrysoscelis calling from a flooded roadside ditch in Medina County, Texas.

Just for a quick comparison, here is the part of a Hyla versicolor call compared to a Hyla chrysoscelis call.  Both call segments are 0.25 seconds long.  Notice that the the H. chrysocelis call has more peaks in that 0.25 seconds, resulting in a faster trill.  In this case, the H. versicolor has 7 peaks (rate of 28 trills  per second) and the H. chrysoscelis has 11 (rate of 44 trills per second).

© Chris Harrison 2012

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