Gray tree frogs can be noisy masters of disguise

July was too hot and dry for man or beast. One of the consequences is that evenings were quiet. I don’t think I heard a frog or toad the entire month.

The gray tree frog

Then the rains came, and the temperature dipped. Toads began to trill each evening, and the nightly chorus of crickets and katydids began. Then one evening during the first August rain, I heard a familiar sound above the drumbeat of raindrops on the metal porch roof. I immediately thought screech-owl because the sound was a monotone trill. But it was too brief for a screech-owl. This trill lasted only a second or so. Then I heard it again. It was a gray tree frog.

Over the years I’ve heard them in Georgia, Oklahoma, Maine and Pennsylvania. The first time was in Georgia’s Okefenokee Swamp. It was during an extended college field trip to catch, see, and hear critters. As alligators bellowed in the distance, gray tree frogs and squirrel tree frogs lulled us to sleep as mosquitoes buzzed inside our tents.

Limited sightings

In Oklahoma it was on a field trip to the northeastern part of the state that I heard this frog, only this time I was an instructor rather than a student. We heard them on night hikes as we listened for owls and whip-poor-wills.

In Maine the sound came from a single tree in a huge, paved, grocery store parking lot. I caught that one and let it use the suction cups on its toe pads to cling to my eyeglasses to show my daughters a live tree frog. I never did figure out how or why it made its way to such an inhospitable island of habitat.

In Pennsylvania, I’ve heard gray tree frogs in many state parks. And in West Virginia, I hear them from my back porch.

Masters of disguise

What’s notable about these recollections is that though I’ve heard many gray tree frogs, I’ve seen few. And that’s typical. Gray tree frogs, when silent, are nearly invisible thanks to incredibly cryptic coloration. They are masters of disguise.

By day, they hide inside cool, dark tree cavities or behind slabs of bark. At night they emerge to eat, sing and mate. When gray tree frogs are abundant, their chorus can be quite noisy.

Look for singing gray tree frogs on wet leaves on the ground, on fallen logs, or even on small tree branches overhanging a pool of water. Move slowly as you zero in on the sound, and use a flashlight to try to spot the singer. Sticky adhesive pads on their toes enable tree frogs to cling tightly to tree trunks and branches. There they wait patiently and silently for tasty flies, beetles, caterpillars, aphids, and moths.

Singing conditions

Though most breeding occurs by early June, gray tree frogs sing throughout the summer, especially on cool, wet nights. If ever you find one, you’ll be impressed by the big sound that comes from such a small creature.

Gray tree frogs usually measure less than two inches in length, and their appearance varies. Depending on light, temperature, moisture, temperature, stress or activity level, they may be gray, green or brown. Thanks to this cryptic coloration, they are extremely difficult to spot, even during the day. Two fairly reliable field marks, however, are bright orange inner hind legs and, unlike most frogs, course skin. Their body is quite warty, though the individual warts are much smaller than those found on toads.

Gray tree frogs leave the safety of trees for the ground for only two reasons.

Mating ritual

Like most amphibians, they gather at water’s edge to make mate. Responding to the males’ song, females locate males and engage in a mating embrace called amplexus. As the female releases as many as 1,000 individual eggs, the male fertilizes them. The eggs drift downward or float away and eventually settle on aquatic vegetation, sticks, or other submerged debris.

In six to 12 days, depending on water temperature, the eggs hatch into tadpoles with red tails. In two to three months, again depending on temperature, the tadpoles transform into small frogs.

As winter approaches, gray tree frogs again leave their arboreal refuge to seek shelter under logs or leaf litter. There they remain dormant until spring, when their cycle of life resumes.

About the Author

Scott Shalaway, who holds a Ph.D. in wildlife ecology from Michigan State University, writes from his home in rural West Virginia. A former faculty member at Oklahoma State University and the University of Oklahoma Biological Station, he has been writing a weekly nature column for newspapers and freelancing for magazines since 1986. Send questions and comments to scottshalaway@gmail.com. You can also visit his Web site, http://scottshalaway.googlepages.com. More Stories by Scott Shalaway

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