Gray Treefrog (Hyla versicolor)

Gray Treefrog (Hyla versicolor)
Photo © by Dave Huth, some rights reserved. Click image for licensing information.

023 Gray Treefrog (Hyla versicolor)
Photo © by Dave Huth, some rights reserved. Click image for licensing information.

Gray treefrog
Photo © by Dave Huth, some rights reserved. Click image for licensing information.

Gray treefrog
Photo © by Dave Huth, some rights reserved. Click image for licensing information.

Scanned Underportrait: Gray Treefrog
Underside scan
Photo © by Dave Huth, some rights reserved. Click image for licensing information.

Gray Tree Frog
Camouflage
Photo © by Dave Huth, some rights reserved. Click image for licensing information.


Description
Males 32-51 mm, females 33-60 mm (Wright and Wright 1949). In general, these frogs have warty skin and prominent adhesive pads on their fingers and toes (Johnson 1987). Their color can vary from green to light green-gray, gray, brown or dark brown (Johnson 1987). Usually, a large irregular star or spot appears on the back (Wright and Wright 1949) A large white spot is always present below each eye (Johnson 1987), although it is less visible and more of an olive color in females (Wright and Wright 1949). The belly is white (Johnson 1987). Males have pale flesh-colored vocal sacs (Wright and Wright 1949). In males, the chin is similar to the belly, with blackish spots (Wright and Wright 1949). In males, the legs are yellow or orange-yellow ventrally. (Johnson 1987), whereas in females, the back of the forelegs, hindlegs and sides are a pale olive gray (Wright and Wright 1949).

The tadpole is approximately 50 mm long, with a long tail. The coloration is scarlet or orange vermilion with black blotches around the edge of the crests (Wright and Wright 1949).

Hyla versicolor is the sibling species of Hyla chrysoscelis (Cope’s Gray Treefrog). These two species are indistinguishable based on external morphology (Conant and Collins 1991). Distinction can be made on the basis of the calls, erythrocyte (red blood cell) size (Matson 1990), and chromosomal complement (Conant and Collins 1991). H. versicolor is a genetic tetraploid, whereas H. chrysoscelis is diploid. The precise distribution of each species is not well established (Conant and Collins 1991). In many areas, these two species live sympatrically (occuring together), and if they do, these species may interbreed (Bartlett and Bartlett 1999).

Perhaps the most striking feature of this frog is its ability to change color to match its environment (metachrosis) – a process which usually requires about half an hour (Logier 1952).

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Distribution and Habitat
Hyla versicolor can be found in Maine, southern Canada (west to Manitoba), Minnesota, South Dakota, southern Kansas, Oklahoma, the Gulf States and northern Florida. It can also be found in parts of Texas and Arkansas (Wright and Wright 1949).

In Canada, the frog occurs in southern Quebec, southern, central and northwestern Ontario and south-eastern and central Manitoba. There is also an isolated population in Fredericton, New Brunswick (Cook 1984).

This treefrog is found in small wood lots, in trees along prairie streams, in large tracks of mixed hardwood forest, and in the bottomland forests along rivers and swamps (Johnson 1987).

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Life History, Abundance, Activity, and Special Behaviors
The orange-yellow coloration on the back of the frog’s legs is considered a “flash” coloration – it is only seen when the frog leaps, when it exposes the underside of the leg, and then is covered when it resumes a sitting position. The sudden flash of contrasting color is thought to confuse predators (Cook 1984).

Breeding season begins at the end of April and ends in August, with breeding events typically concentrated during spring rains in May and June (Oldfield and Moriarty 1994). The female lays approximately 30 to 40 eggs of a brown and cream or yellow color in small scattered masses or packets on the surface of quiet pools. The eggs, measuring about 1.1-1.2 mm, are attached to the vegetation. Hatching occurs at 4-5 days (Wright and Wright 1949).

This frog is freeze-tolerant (Schmid 1982; Storey and Storey 1985).

Hyla versicolor has been found to be significantly less prone to infection by the trematode parasite Ribeiroia ondatrae than the sympatric species Bufo americanus, with metamorphic treefrogs harboring far less of a trematode parasite load and little associated mortality or deformities. H. versicolor may have higher immunity to this parasite (Johnson and Hartson 2009).

This species is classified as Least Concern. However, habitat preservation is still important. Hyla versicolorrequires terrestrial habitat adjacent to breeding sites as well as the breeding wetlands, with a minimum suggested terrestrial habitat buffer of 60 m surrounding the main breeding pond (Johnson and Semlitsch 2003).

H. versicolor is one of the frog species which has been used to demonstrate the insufficiency of many of the pesticide studies conducted by pesticide manufacturers under current EPA regulations. H. versicolor tadpoles are susceptible to mortality from exposure to low concentrations of the pesticide carbaryl, with 10-60% of carbaryl-exposed tadpoles dying in laboratory experiments. This mortality rate shoots up to 60-90% if the tadpoles are simultaneously exposed to both stress and low concentrations of carbaryl, with stress induced experimentally by placing a caged predator in the water (Relyea and Mills 2001). Thus studies examining only low concentrations of pesticide without considering synergistic effects from other factors may be highly likely to underestimate the negative effects of the pesticide.

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