Gray tree frogs live in forested areas throughout the eastern United States and southern Ontario. They are about two inches long and have warty, blotchy skin that ranges in color from green to brown to gray with a white spot under each eye. Their scientific name is Hyla versicolor, which comes from the Latin for "variable color." They are so named for their ability to alter their skin color, depending on temperature and time of day.
Males and females look the same except that the underside of the male’s chin is darker because he has a sac in his throat for calling during mating season and the female does not. The male’s call is a shrill chirp that lasts for one second and is repeated every four seconds.
Males begin their mating calls in early spring from trees and bushes close to standing water. They are highly territorial and will fight other males to defend their areas. Fighting consists of wrestling, shoving, kicking, and head butting, and it lasts until the weaker male retreats. The female starts the mating process by approaching a calling male and touching him before rotating 90 degrees. She then lays her eggs in shallow water. The eggs hatch after a few days, and the tadpoles metamorphose into young frogs after about two months. Young gray tree frogs are almost always bright green, and they stay this way for some time before taking on their adult coloration.
Gray tree frogs are nocturnal, spending their days high in trees and climbing down at night to forage on the ground for insects, spiders, mites, and snails. Their hands and feet are webbed, and on the tip of each digit there’s a large, sticky pad that helps them get a better grip. In the winter, they bury themselves beneath logs, leaves, and dirt and produce an antifreeze-like fluid called glycerol to keep from freezing.
Gray tree frogs are a source of food for a wide variety of predators, such as skunks, opossums, raccoons, and snakes. They have bright yellow or orange coloring on the inside of their thighs that they can flash at predators to confuse them when under attack. They also release a slimy fluid that irritates their predators' eyes and mucos membranes. If you should be lucky enough to find one, make sure to wash your hands well if you handle it.
We were especially lucky this winter to have a lovely Gray Tree frog overwinter in one of our potted plants. While he lived indoors in our plants all winter, he never came out despite the household temperatures. We noticed him in a fern in April and released him back out into the forest once things warmed up a little.