General Adult Description: The Cope’s Gray Treefrog medium-sized frog with adults usually ranging from 1–2 inches (2.5–5 cm) in length. The dorsal coloration of adults can either be gray or bright green in color, and individuals have the ability to change colors within a few hours. This coloration is often determined by environmental factors. Irregular dark gray or brown blotches are often present on the back as well but may be difficult to observe depending on the coloration of the individual. The ventral coloration is typically pale gray or cream in color. Typically, a gray stripe passes through the eyes and continues posteriorly to the jaw to the underside of the individual. On the inside thigh of adults is a large patch of bright yellow that is often concealed when individuals are resting. Because this is highly arboreal, adults have large toe pads at the ends of each of the digits that allow it to climb proficiently. Adult males can be distinguished from females by the presence of a dark colored throat (females have a light colored throat).
General Larval Description: Larval Cope’s Gray Treefrogs can easily be distinguished from all other tadpoles by the presence of red or orange pigmentation in the tail fin. Tadpoles also have a highly arching, mottled tail fin and lateral eyes. This bright coloration on the tail serves as a lure to direct predatory strikes away from the body and towards the tail.
Call Description: Male Cope’s Gray Treefrogs produce a loud, harsh trill which is high in pitch relatively fast.
Similar Species: The Grey Treefrog (Hyla versicolor) is separate species from the Cope’s Gray Treefrog; however, both are identical in appearance. Most aspects of their ecology are similar and in some regions, both Gray Treefrogs and Cope’s Gray Treefrogs can be found in the same area. There are two main differences between these two species. These two species differ in the number of chromosomes that they have and in characteristics of their calls. The Cope’s Gray Treefrog has two sets of chromosomes (diploid) and has a harsher, higher pitched call (see Call Description above). The Gray Treefrog has four sets (tetraploid) of chromosomes and a slower, lower pitch, more melodic trill. If only one species is present and calling, it may be difficult to discern which call is being heard without the other to compare it to. Recently captured individuals in South Dakota (Brookings, Clay, Roberts, Union counties) have all been Cope’s Gray Treefrogs. Uncertainty has surrounded whether both species actually occur in the state, but multiple lines of evidence suggest that only Cope’s Gray Treefrogs occur in the state. When at all possible, any observations of this species should be accompanied call recordings of individuals.
Behavior: During the winter, this species hibernates above the frost line in the soil under debris. This species produces plasma glycerol, an antifreeze compound, to counteract the effects of freezing on tissues. Cope’s Gray Treefrogs are primarily nocturnal and forage on a wide variety of invertebrates.
Reproduction: Males begin calling at wetlands or surrounding trees or shrubs in early June. Females lay anywhere from 900–3,000 eggs in clusters of 20–90 eggs on submerged vegetation. Eggs hatch in 4 to 5 days as tadpoles and typically undergo metamorphosis within two months.
Habitat: Cope’s Gray Treefrogs can be found breeding in riparian wetlands or fishless ponds, or flooded agricultural fields near forests or other tree cover. Adults move to these wetlands to breed but then return to upland, forested habitats where they are difficult to detect. Outside of breeding, adults are rarely encountered on the ground.
Species Range: This is common throughout most of the central and eastern United States. This may not be completely accurate as most maps may still combine this species with the Gray Treefrog (Hyla versicolor) due to them being identical in appearance.
South Dakota Range: The Cope’s Gray Treefrog is restricted to riparian forests in southeastern South Dakota and along the eastern border up to the northeast corner of South Dakota (Roberts Co.). A single male was heard calling in late summer in Custer State Park and may represent an introduced population. Additionally, a population near Oahe Dam in Pierre has been reported, though it is uncertain if this represents and introduced population or relict peripheral population.
South Dakota Status: This species is monitored by the South Dakota Natural Heritage Program. Any sightings of this species should be reported to South Dakota Game, Fish and Parks (report observation).
Account written by Drew R. Davis and Amanda M. Hegg