The members of the gray treefrog complex average one and one-fourth to two inches in length. Cope’s gray treefrog and the gray treefrog are two separate species, but they appear identical externally. Their calls are different, however. The call of the gray treefrog is a musical trill with from 17 to 35 pulses per second. The call of Cope’s gray treefrog is a high pitched buzzing trill with 34 to 69 pulses per second. They also have different numbers of chromosomes. The gray treefrog is tetraploid while Cope’s gray treefrog is diploid. The body is usually gray or green but with many variations. A light spot is present beneath each eye. The concealed surfaces of the hind legs are bright orange mottled with black. The back is warty and has a star-shaped or irregular dark blotch. An adhesive pad is present on the tip of each toe. The tadpole’s tail is marked with red and black.
The gray treefrog and Cope’s gray treefrog make up the gray treefrog complex. These species may be found statewide in Illinois. The gray treefrog lives in woodlands near water. In dry conditions it may be found in dead trees, under bark or in rotten logs. Breeding occurs from late April into August. The male’s call is a musical trill similar to the call of the red-bellied woodpecker. Eggs are deposited in almost any water-filled depression. Packets of two to three dozen eggs are attached to vegetation at the water’s surface. A total of 1,800 eggs per female may be deposited. Hatching occurs in a few days. Larvae transform from May through August, about two months after hatching. The gray treefrog eats arthropods (spiders, insects, mites and others).