Gray Treefrogs - Hyla chrysoscelis/versicolor

Cope's Gray Treefrogs - Hyla chrysoscelis

Common Gray Treefrogs - Hyla versicolor

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Hybrid "Gray" Treefrogs - Hyla chrysoscelis X Hyla avivoca

Although there are two separate species, they are often mistaken one for the other. Because of their amazing physical similarities, as well as that of habitat and range, the only way to distinguish between them in the field is by call. Hyla versicolor has a slow trill, while Hyla chrysoscelis has a faster, higher pitched trill. Hyla versicolor has twice the chromosome number of Hyla chrysoscelis. The Cope's X Bird-voiced hybrid has a call very similar to Hyla versicolor. The diagnostic features, natural history, and range listed below apply, for the most part, to both species.

Diagnostic Features:
- Size: 1.25 to 2.5 inches (32 to 62 mm)
- Color:
  - Typically gray, various shades of brown, green, or even nearly white but highly variable with environment and mood.
- Other:
  - Comparatively large treefrog
  - Discernible light spot under eyes
  - Warty dorsal surface, but a individual can transform to a smooth glossy surface
  - Dark bars on hind limbs
  - Bright orange or yellow color on hidden surfaces of thighs
  - Large toe pads present
- Similar Species:
  - Bird-voiced Treefrogs: smaller size, concealed surfaces of the thigh and groin are pale yellowish green to greenish or yellowish white. There is a divided pustule at the base of the fourth fingers on each hand of Bird-voiced Treefrogs(undivided in the Gray Treefrogs). The call is a series of piping, bird-like whistles issued in rapid succession (it is a musical trill in H. versicolor, and a buzzing trill in H. chrysoscelis). The Bird-voiced Treefrog prefers wooded swamps, where Gray Treefrogs are less likely to occur.
  - A hybrid between Bird-voiced Treefrogs and Cope's Gray Treefrogs occurs in Georgia. It's voice is similar to H. versicolor (not known to occur in Georgia). It has thigh and groin colors that are intermediate. It can be up to 10% of the calling "gray" population where both species breed. Calls in response to Cope's Gray Treefrogs, not Bird-voiced Treefrogs. It's a sterile hybrid.
- Sexual Dimorphism:
  - Males average smaller than females
  - Males may have a darkened throat during breeding season.
Natural History:
- Habitat:
  - These frogs are found in wooded areas.
- Behavior:
  - They are nocturnal and forage in the trees and shrubs. They descend to the ground only to breed.
- Breeding:
  - Breeding occurs from March to July, depending on the temperature.
  - Rain also may trigger breeding activity
  - Scattered groups of 10 to 40 eggs are laid on the surface
  - Breed in shallow ditches, puddles and ponds, almost any flooded container will do
Voice: Sonogram : Call chrysoscelis ( Fannin, Dawson, Terrell, & Fayette Counties ) : Call versicolor : Call avivoca x chrysoscelis ( Walton County )
- Musical trill
- Hyla chrysoscelis: faster and higher pitched
- Hyla versicolor: slower and lower pitched than H. chrysoscelis
- Cope's X Bird-voiced call very similar to H. versicolor, a soft call as well.
  Call of Hybrid (single call between two Cope's calls followed by calls in mixed chorus)
Tadpoles:
- Hyla chrysoscelis
  - Tadpole stage: 45 - 64 days
  - Transformed size: 13 - 20 mm
- Hyla versicolor
- LTRF 2/3; narrow midventral gap in marginal papillae absent; eyes lateral; Rocky Mountains and east; P-3 long, P-2/P-3 ca. 1.0
- midventral marginal papillae biserial; dense patch of small submarginal papillae ventrolaterally; length of one side of A- 2/width of medial gap > 3.4;
- color and pattern extremely variable, in some areas, clear parts of fins reddish, yellow or orange coloration late in development; in some areas, fins remain relatively clear vs. heavily marked with large black blotches elsewhere (highly variable and no known way to distinguish between these diploid/tetraploid tadpoles)
- Tadpoles of Gray Treefrogs often have reddish tails mottled with dark pigment.

Range:

In North America, these treefrogs are found from Maine in the north and northern Florida in the south, to the great plains west of the Mississippi River.

In Georgia, they are found throughout the state. Little work has distinguished the two species. Hyla versicolor has not been definitively found in the state, however, there is a hybrid who's call is very similar to Hyla versicolor: Cope's Gray X Birdvoiced Treefrogs that appears in Georgia.


Cope's Gray Treefrogs	Cope's X Bird-voiced Hybrid

In Light Blue: Williamson, Gerald K. & Moulis, Robert A., Distribution of Amphibians and Reptiles in Georgia, Special Publication No. 3, Savannah Science Museum, Inc. Savannah, Georgia, 1994
In Green: Sound Recordings
In Yellow: From Both '94 study and Sound Recordings
In Magenta: Photograph, not found by '94, may or may not be sound record
In Medium Blue: Photograph and in '94 study, may or may not be sound record
In Orange: County Record by other Herp Atlas Volunteers
In Red: US Distribution from various sources

May 25, 2008 - wwknapp@mindspring.com