Cope's gray tree frog, also called the southern gray tree frog is a species of tree frog found in the United States. It is almost indistinguishable from the gray tree frog, and shares much of its geographic range. Both species are variable in color, mottled gray to gray-green, resembling the bark of trees. These are tree frogs of woodland habitats, though they will sometimes travel into more open areas to reach a breeding pond. The only readily noticeable difference between the two species is the mating call — Cope's has a faster-paced and slightly higher-pitched call than D. versicolor. In addition, D. chrysoscelis is reported to be slightly smaller, more arboreal, and more tolerant of dry conditions than D. versicolor.
Taxonomy
described the species in 1880. The specific name, chrysoscelis, is from Greek chrysos, gold, and scelis, leg. Microscopic inspection of the chromosomes of D. chrysoscelis and D. versicolor reveals differences in chromosome number. D. chrysoscelis is diploid, having two complete sets of chromosomes, the usual condition in vertebrates. D. versicolor is tetraploid, having double the usual number of chromosomes. Generally, D. versicolor is believed to have evolved from D. chrysoscelis in the last major ice age, when areas of extremely low temperatures divided populations. Despite currently sharing habitat, the two species generally do not interbreed.
Description
Both D. chrysoscelis and D. versicolor have black-marked bright orange to yellow patches on their hind legs, which distinguishes them from other tree frogs, such as D. avivoca. The bright-yellow pattern is normally hidden, but exposed when the frog leaps. This "flash pattern" likely serves to startle a predator as the frog makes its escape. Similar hidden bright patterns are common in various Lepidoptera, for instance moths of the genusCatocala. Both species of gray tree frogs are slightly sexually dimorphic. Males have black or gray throats in the breeding season, while the throats of the females are lighter. Skin secretions from this species may be irritating or toxic to mouth, eyes, other mucous membranes.
Distribution and habitat
The range of D. chrysoscelis is more southerly; it is apparently the species found in the lower elevation Piedmont and Coastal Plain of Virginia and the Carolinas. In those areas, D. versicolor may be present only in the Appalachians. The bird-voiced tree frog, D. avivoca, is similar to D. chrysoscelis and D. versicolor, but is smaller.
Behavior
In the Southeastern United States, Cope's gray tree frog breeds and calls from May to August. Isolated males start calling from woodland areas during warm weather a week or more before migrating to temporary ponds to breed. There they form aggregations and call together. Chorusing is most frequent at night, but individuals often call during daytime in response to thunder or other loud noises. Eggs are laid in batches of 10 to 40 on the surfaces of shallow ponds and other small bodies of water. These temporary bodies of water usually lack fish, and females preferentially lay their eggs in water bodies that lack fish or other predatory vertebrates and have lower desiccation risk. Eggs hatch in about five days and metamorphosis takes place at about 45–65 days. Dryophytes chrysoscelis is capable of surviving temperatures as low as –8 °C.
