Gray Tree Frog

The gray tree frog is a small tree frog native to a broad swath of eastern North America, from the Gulf Coast north into the Great Lakes region and southern Canada. It can shift its skin color within minutes between mottled gray, brown, and green depending on temperature, humidity, and the background it rests against, making it an effective bark-mimicking climber. It forms a nearly identical cryptic species pair with Cope's gray tree frog, distinguishable mainly by a slower trilling call and a different chromosome count rather than by appearance. In winter it survives freezing temperatures by producing natural cryoprotectants, including glycerol and elevated glucose, that prevent ice crystals from forming inside its cells while it overwinters beneath leaf litter.