Forest Preserves of Cook County
May 12, 2021
Did you know we have native tree frogs in Cook County? It’s likely you’ve walked right past these tree-living amphibians without noticing!
The gray tree frog’s scientific name, Hyla versicolor, means “variable color.” Although gray is included in their name, this arboreal—or tree dwelling—frog’s skin changes color in response to its environment. They may be gray, brown or green, or a bit of all three with a white underside and yellow on the inner part of their thighs. Their bumpy camouflaged skin helps them hide from predators.
As its name suggests, adult gray tree frogs spend much of their life in the trees in wetland and woodland habitats in the eastern part of the United States and will venture into neighborhoods with similar habitats. This frog secretes a mucus from the membranes on their large, ridged toe pads that acts like a glue to help them climb and attach to the trunk of trees and shrubs.
The 1- to 2-inch gray tree frog is nocturnal and will hunt for insects when it’s dark and stay hidden in the bark of trees when they aren’t active during the day. At the end of April, male tree frogs will begin gathering in wetlands and ephemeral ponds to aggressively defend their territories and call for potential mates. Interested females will respond by laying their eggs in the water the male will then fertilize. They can live up to nine years in the wild.
Like our local wood frogs, gray tree frogs have a superpower to survive through Illinois’ harsh winters. Their body produces large amounts of glucose that acts as an antifreeze to survive freezing temperatures.
Where to find them in your neighborhood: Under the right conditions in the summer months, you might find gray tree frogs clinging to your window or screen door trying to eat the moths and insects gathering at your outside light.
Click here to listen to the unique sounds of the eastern gray tree frog.
Interested in helping tree frogs? Join us on Saturday, May 22, for a Calling Frog Survey program at Little Red Schoolhouse Nature Center. Attendees will use their sense of hearing to identify which frogs are calling, and the data collected will be used as part of the Calling Frog Survey for the Chicago Wilderness Region.