The three frogs to begin calling as early as late February in Indiana are the Spring Peeper (Pseudacris crucifer), Western Chorus Frog (Pseudacris triseriata), and Wood Frog (Rana sylvatica). It is usually March before we begin to hear them in the northern part of the state, however.
In mid- to late-March, we begin to hear the long, flute-like, tranquill trill of the American Toad (Bufo americanus). This species can be up to three-and-a-half inches long and is easily recognizable by having small dark spots enclosing one or two warts each on their backs. The underside of the American Toad is also usually heavily dark splotchy. American Toads are common throughout most of eastern North America, most commonly found in grasslands and open woods. They are also commonly found in suburban and agricultural areas. Be careful if you handle an American Toad, because if they pee on you, you will get warts. JUST KIDDING!! That's just a myth. But they do have a large gland behind each eye, called the parotoid gland, that contains a bitter chemical that is toxic to predators, so you probably shouldn't eat one.
Photo from www.in.gov/dnr/fishwild/3333.htm
The Eastern Gray Treefrog (Hyla versicolor) is very similar to the Cope's Gray Treefrog (Hyla chrysoscelis), and can really only be distinguished by call and genetic analysis. However, Cope's Gray Treefrogs are not known from the northern part of Indiana. Eastern Gray Treefrogs are up to about 2 inches long as adults. Their appearance changes from the time they are young until they are adults, and as adults, their color can also change depending on temperature and the color of their surroundings (hence the specific epithet versicolor, meaning "of various colors"). As young frogs, Eastern Gray Treefrogs are green and very smooth. They begin to develop a warty texture as they mature.
By the time they are adults, their color can range from putty white to pale green to almost black, with a somewhat warty skin and black and dark gray patterns.Eastern Gray Treefrogs are found in the eastern United States, with the exception of the southeast, and range north into southern Canada. Most commonly, they are found in moist forests surrounding swamps or ponds, but you can hear them calling from almost any forested habitat from late April or early March into the middle of summer. Eastern Gray Treefrogs produce a musical, bubbly trill that ususally lasts just a few seconds; their calls are often confused for Red-bellied Woodpeckers.