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Two gray treefrogs? Similar, but different
How can you tell the Cope's gray treefrog (Hyla chrysoscelis) and the gray treefrog (Hyla versicolor) apart when they look exactly the same? It is amazing to learn that these two species are nearly identical.
Both found in the eastern United States (see distribution maps below), there are two ways to distinguish these species. First, they differ in the number of chromosomes they have. Cope's has two sets of chromosomes (like humans) and the gray treefrog has double that number – four sets of chromosomes.
Source for Distribution Maps:
Laura (Leininger) Blackburn, Michael J. Lannoo, & Priya Nanjappa, April 2002, Current Distributions of Selected Amphibians in the United States, in National Atlas of the United States, see http://nationalatlas.gov.
The only additional difference can be heard in the mating calls of the males. The Cope's gray treefrog has a short, loud flute-like trill, which lasts up to 30 seconds. It is faster as well as a harsher sounding call than gray treefrog. The gray treefrog has a longer trill that is much more musical sounding then the Cope's.
Since these species can be difficult to tell apart when you are conducting your surveys, you may see them listed as a species complex on your Frogwatch USA state species list. In states where their distributions overlap, we offer the choice of both individual species and the option of Unknown gray treefrog species complex (Hyla chrysoscelis/versicolor) for cases where you are unsure of which species you are hearing in the field.
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