Gray tree frogs are fairly large tree frogs (1 – 2 inches in length) with rough, warty skin. Despite their name, not all gray tree frogs are actually gray. They vary in coloration from mottled gray or brownish-gray to light green.
Gray tree frogs can change color depending on the temperature, light, or the color of their surroundings. They may appear gray to match the bark of a tree, or green to blend in with leaves – and tend to become darker when their environment is cold or dark.
In general, gray tree frogs range in color from a mottled grayish green or solid green to a gray or creamy white color.
That said, it’s important to note that gray tree frogs don’t change color as fast as a chameleon. However, the color change is still fast enough to keep these frogs camouflaged and hidden from predators.
Gray Tree Frog Tadpoles Have Inconsistent Coloring
Gray tree frogs hatch from eggs and start their lives as tiny tadpoles that live entirely in the water. Tadpoles are very different from adult gray tree frogs. This is because they are highly adapted for their fully aquatic life.
They have gills and a flat paddle-like tail fin to help them move in the water.
Gray tree frog tadpoles have inconsistent coloring, which may include different shades of brown or olive green. The body and tail are patterned with many specks of black and gold – and black blotches may be present around the edge of the tail.
Interestingly, gray tree frog tadpoles can develop a bright red coloration on their tail when they are exposed to predators such as dragonfly larvae.
The ability of a single genotype to develop alternative traits in different environments is known as “phenotypic plasticity.
Studies suggest the red pigments in the tail may help to misdirect predator attacks.
Young Gray Tree Frogs Are Usually Bright Green
After about 1- 2 months, the tadpoles will go through a process known as metamorphosis, in which they will transform into juvenile frogs.
During metamorphosis, the thyroid gland secretes a growth hormone called thyroxine.
This hormone triggers the tadpoles to:
- Lose the gills, and develop lungs for breathing air
- Absorb the tail into the body
- Grow strong legs for moving on land
- Remodel other organs to form an adult frog
Once this process is complete, tiny gray tree frogs (approximately 0.6 inches in length) called “froglets” or “metamorphs”, will leave the water and live on land.
The newly transformed froglets are almost always bright emerald green with smooth skin, and they stay this way for some time before taking on their adult coloration.
Adult Gray Tree Frogs Have Varied Coloration
Adult gray tree frogs range to just over 2 inches long and have granular (almost warty) moist skin.
They have a light spot beneath the eye and the skin on their inner thigh is bright yellow or orange, which is most visible when the frog is jumping or moving.
Adult gray tree frogs have a varied body coloration, which may range from green to light greenish gray, gray, brown, or dark brown.
There is often a large irregular star-shaped dark splotch on the back, but this can come or go, and some individuals are uniformly whitish, light gray, or some shade of green.
That said, gray tree frogs have the ability to change color depending on activities and the environment.
A gray tree frog may be whitish to gray to blend in with tree bark, or pale green to dark green when resting on foliage. These frogs can change color dramatically in a matter of minutes, though at a slower rate than a chameleon.
Besides substrate color, other reasons a gray tree frog may change color include:
- Temperature – They tend to become darker when it is cold
- Time of day/light – They tend to become darker at night and lighter in color in warm sunny areas
- Time of year – They tend to become more greenish during the breeding season
How Do Gray Tree Frogs Change Color?
Coloration in animals is produced by reflection and scattering of light by cells and tissues and by absorption of light by chemical pigments within cells of the skin.
In ectotherms such as frogs, cells containing pigments are called chromatophores and are largely responsible for generating skin color.
In frogs, there are three main types of chromatophores:
- Xanthophores, which contain yellow-red pigments
- Iridophores containing colorless stacks of crystals or platelets that reflect and scatter light to generate hues such as blue and white
- Melanophores, which contain black melanin pigment
The melanophores play an important role in color change.
They are large, star-like cells with long “arms” that extend towards the skin’s surface.
Color change occurs due to the movement of “packets” of melanin pigment (melanosomes) within the melanophores.
When melanin pigment is clustered within the center of the cell, the skin appears very pale – and when it is dispersed through the arms of the melanophores towards the skin’s surface, the frog appears dark.
Because the arms of the melanophores extend between and over the other types of chromatophores (generating different colors), varying the degree of dispersion of the melanin can hide or reveal those chromatophores, changing the animal’s color.
Color change may happen due to various “triggers” including temperature or light. However, most importantly, gray tree frogs change color in response to their surroundings.
They need to observe their surroundings so that they know what color to change to. Information about their surroundings is then processed by the brain, and the brain sends signals to chromatophores.
Dead Gray Tree Frogs Are Almost Always Gray
Interestingly, when a gray tree frog dies, it almost always turns gray. This gray coloration is also observed in gray tree frogs in unnatural surroundings, such as in people’s homes, or resting on man-made objects.
Since gray tree frogs change their skin color using neural impulses, when one of these frogs dies, it stops sending those signals and turns to its ‘natural’ color, which is predominantly gray.
Common Questions About Gray Tree Frog Coloration
Can gray tree frogs change color? Gray tree frogs can change color depending on the temperature, light, or the color of their surroundings. They tend to be whitish to gray when resting on tree bark, and pale green to dark green when resting on foliage. These frogs also tend to become darker when their environment is cold or dark.
Conclusion
Despite their name, not all gray tree frogs are actually gray. They vary in coloration from green to light greenish gray, gray, brown, or dark brown.
However, they can change their color dramatically in a matter of minutes, based on various “triggers” including temperature, light, and the color of their surroundings.
Adult gray tree frogs generally tend to become more greenish during the breeding season.
Also, young gray tree frogs are almost always bright green right after metamorphosis and they stay this way for some time before taking on their adult coloration.
Sources:
McCollum, S. A., & Van Buskirk, J. (1996). Costs and Benefits of a Predator-Induced Polyphenism in the Gray Treefrog Hyla Chrysoscelis. Evolution, 50(2), 583–593. https://doi.org/10.2307/2410833
AmphibiaWeb. Hyla versicolor Eastern Gray Treefrog. University of California, Berkeley, CA, USA.
Virginia Herpetological Society. Gray Treefrog Hyla versicolor.
Devi Stuart-Fox (2013). How do chameleons and other creatures change color? University of Melbourne.
Mueller, L. 2006. “Hyla versicolor”, Animal Diversity Web.