green on green

Hiding in plain sight by matching the color of your skin to the color of the background is useful for predators stalking their prey or prey trying to escape predation.  It’s also useful in confusing photographers about where to aim their cameras.  Case in point: I saw the bushes moving, wondered if it was a bird, thought it might be a chipmunk, but stared right at the little critter for a full minute before I figured out what it was.

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A gray tree frog in green phase hiding in plain sight.  It wasn’t this obvious without the zoom on the camera to help pinpoint its location.

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It’s scientific name gives a hint to its ability to change colors: Hyla versicolor. Usually it appears mostly gray with green splotches.

Many species of fish, amphibians, and reptiles have the ability to change color and outward appearance by contracting or expanding the chromatophore (pigment-containing) cells in their skin.  This chameleon-like ability can assist them in better regulating their body temperature, or as suggested, in achieving the kind of camouflage that helps them evade their predators or fool their prey. It is thought that the animals’ eyes perceive the color spectrum of their environment and send neural signals to skin chromatophores to effect the appropriate color changes.

In cases where there doesn’t seem to be a clear message about the color of the background, Gray Treefrogs are often mottled gray and green, or just remain gray, as illustrated below.

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Hmm… water in a bird bath? Not sure what color to be.

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Gray treefrog sitting on the side of a dish pan, next to green vegetation — again, it’s confusing about what color to be.

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Gray treefrog sitting on an orange dahlia — no possibility of a match here.

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Green-colored Gray treefrog on the ledge of a wooden door? Clearly a bad match.

Fotogenic Frog

gray tree frog

A dahlia flower fell down into some yews, and a shy tree frog decided it was a fine place to rest.

The Eastern Gray Treefrogs are most often found on vegetation, usually high up in the trees, rather than near water, as their name implies.  Actually, I most often see them in the outdoor tank we use to water potted plants.

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I picked up the lid of the water tank to see if it needed filling, and found this little guy waiting for me. I don’t know how they get in, and I wonder how they get out.

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They are adept at climbing vertical surfaces, even slick ones, using their sticky, enlarged toepads.

Their skin has a warty appearance, like that of toads, and they manage to stay hydrated without taking refuge in pools of water, even during hot days.  Gray Treefrogs tend to hunt at night, often near an outdoor light fixture where they can capture insects coming to the light.

gray tree frog

Interesting eye color in this individual, and you notice patches of green in the otherwise gray skin.

Skin color in these frogs is highly variable (hence their scientific name — Hyla versicolor).  Three layers of chromatophores in the skin (color-producing cells) combine to produce the color pattern, which can change (very slowly) from near white to very dark brown, with variations of mottled green and gray in between. Treefrogs don’t match their environment perfectly the way a chameleon does, but their color changes do help camouflage them in their environment somewhat.  More on how this is accomplished in the next post!  Stay tuned.

gray tree frog

oops, there are no red-orange pigments in those chromatophores, so color matching this dahlia would be tough.