Cope's gray treefrog

Cope's gray treefrog[2] (Dryophytes chrysoscelis), also called the southern gray treefrog is a species of treefrog found in the United States. It is almost indistinguishable from the gray treefrog (Dryophytes versicolor), 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 treefrogs 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.[3]

Cope's gray treefrog
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Amphibia
Order: Anura
Family: Hylidae
Genus: Dryophytes
Species:
D. chrysoscelis
Binomial name
Dryophytes chrysoscelis
(Cope, 1880)
Synonyms
  • Hyla chrysoscelis Cope, 1880

Taxonomy

Edward Drinker Cope described the species in 1880. The specific name, chrysoscelis, is from Greek chrysos, gold, and scelis, leg.[4]

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
Showing variation in color

Both D. chrysoscelis and D. versicolor have black-marked bright orange to yellow patches on their hind legs, which distinguishes them from other treefrogs, such as D. avivoca.[3] 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.[5] Similar hidden bright patterns are common in various Lepidoptera, for instance moths of the genus Catocala.[6] Both species of gray treefrogs are slightly sexually dimorphic. Males have black or gray throats in the breeding season, while the throats of the females are lighter.[7]

D. chrysoscelis male showing black throat

Skin secretions from this species may be irritating or toxic to mouth, eyes, other mucous membranes.[8]

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.[3] The bird-voiced treefrog, D. avivoca, is similar to D. chrysoscelis and D. versicolor, but is smaller (25–50 mm in length vs 32–62 mm for the gray treefrog).

Behavior
Metamorphs are typically green

In the Southeastern United States, Cope's gray treefrog 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 (choruses) 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.[9][10][11] Eggs hatch in about five days and metamorphosis takes place at about 45–65 days.[3][7][12]

Dryophytes chrysoscelis is capable of surviving temperatures as low as –8 °C.[13]

References
  1. IUCN SSC Amphibian Specialist Group (2014). "Hyla chrysoscelis". IUCN Red List of Threatened Species. 2014. Retrieved 2015-01-17.CS1 maint: ref=harv (link)
  2. Hyla chrysoscelis, Amphibian Species of the World 5.6
  3. Martof, B. S., et al. (1980). Amphibians and Reptiles of the Carolinas and Virginia. Chapel Hill: University of North Carolina Press. ISBN 0-8078-4252-4.
  4. Family Group Names in Diptera Archived 2008-04-11 at the Wayback Machine
  5. Tesler, P. Exploratorium The Amazing, Adaptable Frog. The Exploratorium. San Francisco.
  6. Sargent. (1969). A suggestion regarding hindwing diversity among moths of the genus Catocala OF (Noctuidae). Archived 2007-03-13 at the Wayback Machine Journal of the Lepidopterists' Society 23: 261-264.
  7. Tyning, T. F. (1990). A Guide to Amphibians and Reptiles. Boston: Little, Brown and Company. ISBN 0-316-81719-8.
  8. "Species profile: Cope's Gray Treefrog (Hyla chrysoscelis)". Savannah River Ecology Laboratory - University of Georgia.
  9. Resetarits, Jr., William J. (1989). "Choice of oviposition site by Hyla chrysoscelis: role of predators and competitors". Ecology. 70 (1): 220–228. doi:10.2307/1938428. JSTOR 1938428.
  10. Pintar, Matthew R.; Resetarits, Jr., William J. (2017). "Out with the old, in with the new: oviposition preference matches larval success in Cope's gray treefrog, Hyla chrysoscelis" (PDF). Journal of Herpetology. 51 (2): 186–189. doi:10.1670/16-019. S2CID 53633353.
  11. Pintar, Matthew R.; Resetarits, Jr., William J. (2017). "Relative predation risk and risk of desiccation co-determine oviposition preferences in Cope's gray treefrog, Hyla chrysoscelis". Oecologia. 184 (2): 423–430. Bibcode:2017Oecol.184..423P. doi:10.1007/s00442-017-3875-7. PMID 28470466. S2CID 2743867.
  12. Rubio, M. Atlanta's Backyard Herps. Accessed 2 June 2013.
  13. Adaptations of Frogs to Survive Freezing

Further reading
  • Mary Hoff (March–April 2014). "Chirp, Croak, Snore". DNR. Minnesota Conservation Volunteer: 32.
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