(Map may reflect historical as well as recent sightings)
Columbia spotted frogs were formerly classified as part of Rana pretiosa, or Spotted frogs. However, Spotted frogs are currently classified as two separate species, the Oregon spotted frog (Rana pretiosa) and the Columbia spotted frog (Rana luteiventris). Researchers found that while the two species are nearly identical morphologically, they differ genetically and occupy different ranges (Green et al. 1997). Green et al. 1997, also indicates there is genetic evidence R. luteiventris may be one species with three subspecies or several weakly-differentiated species (Green et al. 1997). Additionally, Funk et al. 2008, found three highly divergent R. luteiventris clades that may actually represent different species.
Description and Life History
Columbia spotted frog (spotted frog) adults are light to dark brown, gray, or olive green with dark spots on the back, sides and legs. The number of spots and spotting pattern varies. The undersides of the legs are orange or yellow; this color may extend up to the chin or be replaced by a light, mottled gray on the chin, chest, and/or belly. Adult body length is 46 to 90 millimeters (1.8 to 3.5 inches). Spotted frogs breed during a short, two-week breeding window anywhere from early April to early June. Eggs are laid at the water surface in large, globular masses of 200 to 500 eggs. Tadpoles are black after hatching and their eyes are located on the top of the head. Tadpoles are approximately 8 to 10 millimeters (.3 to .4 inches) in length at hatching and commonly metemorphose at 70 to 75 millimeters (2.7 to 2.9 inches). Metamorphosis usually occurs from late July until freezing weather. The lifespan of spotted frogs can be seven to nine years (Engle 2001). Spotted frog diets can vary widely. Adults eat insects, mollusks, crustaceans, and arachnids; larvae eat algae and organic debris. Predators of spotted frog adults include herons and garter snakes, and the recently introduced bullfrogs. In addition, larvae may be consumed by the larvae of dragon flies, predacious diving beetles, fish and garter snakes.
Spotted frogs are highly aquatic and live in or near permanent bodies of water, including lakes, ponds, slow streams and marshes; movements of spotted frogs are limited to wet riparian corridors. Spotted frogs occur in riparian areas, where emergent vegetation and standing water are present, within the sage-juniper shrublands (Engle 2001). Standing water, flooded meadows, and willows provide breeding, foraging, and overwintering habitat. Most spotted frogs hibernate and aestivate; hibernation occurs in spring-fed ponds with willows (Engle 2001).
Columbia spotted frogs occur from Alaska and most of British Columbia to Washington east of the Cascade Mountains, Idaho, the Bighorn Mountains in Wyoming, the Mary’s, Reese, and Owyhee River systems in Nevada, the Wasatch Mountains, and the western desert of Utah. There are currently four recognized populations of Columbia spotted frogs: Northern, Great Basin, Wasatch, and West Desert. Columbia spotted frogs within the Northern population are considered to be abundant; however, the other three populations (Great Basin, Wasatch, and West Desert) are either declining or almost extirpated. Currently, only the Great Basin populations of Columbia spotted frogs that occur in Oregon (Malheur, Lake, Harney and possibly Grant Counties) are considered a candidate species by the US Fish and Wildlife Service (USFWS 2009).
Reasons for Decline
The causes of decline are not fully understood, but like most amphibians a major threat is the destruction, fragmentation and degradation of wetlands. The introduction of non-native predators such as bullfrogs, bass and predatory freshwater fish species are believed to contribute to their decline.
References and Links
Engle, J.C. 2001. Population Biology and Natural History of Columbia spotted frogs (Rana luteiventris) in the Owyhee Uplands of Southwest Idaho: Implications for Monitoring and Management. M.S. Thesis, Boise State University, Boise, Idaho. 66 pages.
Funk, W. C., C. A. Pearl, H. M. Draheim, M. J. Adams, T. D. Mullins, and S. M. Haig. 2008. Range-wide phylogeographic analysis of the spotted frog complex (Rana luteiventris and Rana pretiosa) in northwestern North America. Mol Phylogenet and Evol.
Gomez, D. 1994. Conservation assessment for the spotted frog (Rana pretiosa) in the Intermountain Region, USFS. U.S. Forest Service; Ogden, Utah.
Green, D. M.; H. Kaiser; T.F. Sharbel; J. Kearsley; K. R. McAllister. 1997. Cryptic Species of Spotted Frogs, Rana pretiosa Complex, in Western North America. Copeia 1997:1-8.