Population Status.  The Columbia Spotted frog (Rana luteiventris) is a candidate for listing under the Endangered Species Act.  Contributing factors to the frogs' decline include destruction, fragmentation and degradation of wetlands, and the introduction of non-native predators, such as bullfrogs, bass and other predatory freshwater fish species.  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.

Description.  Great Basin 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 mm.  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 mm in length at hatching and commonly metemorphose at 70 to 75 mm. 

Diet.  Adult spotted frogs feed on a variety of insects, mollusks, crustaceans and arachnids.  Tadpoles feed on decaying vegetation and algae.

Habitat. Spotted frogs are highly aquatic and live in or near permanent bodies of water, including lakes, ponds, slow streams and marshes.  They are generally found in or near a perennial body of water that includes areas of shallow water and emergent vegetation. The frogs use the floating vegetation as basking platforms, and as cover to hide from predators. Standing water, flooded meadows, and willows provide breeding, foraging, and overwintering habitat; most spotted frogs hibernate in spring-fed ponds with willows.

Project Location. Dry Creek is a tributary to the Owyhee River and located in Malheur County in southeast Oregon.  Dry Creek is characterized by steep canyons, scour pools and narrow stream reaches with boulders, cobbles and sandy substrate.  Vegetation along Dry Creek consists of sedges, rushes, forbs and occasional willows and cattails.  Dry Creek has the largest known Columbia spotted frog population on the Vale Bureau of Land Management (BLM) District (excluding the Baker Resource Area, which is most likely comprised of the Northern population segment of the Columbia spotted frog).  Dry Creek was chosen for long-term population monitoring not only for its large population of Columbia spotted frogs, but also because the population is relatively isolated with no connectivity to other watersheds. 

Project Description.  This study was initiated in 2001 by the Vale District Bureau of Land Management and the U.S. Fish and Wildlife Service’s Snake River Fish and Wildlife Office in Boise, Idaho in order to monitor long-term population trends, demographics and movement patterns for Columbia spotted frogs in Dry Creek.  The Snake River Fish and Wildlife Office was responsible for the monitoring along Dry Creek until 2006.  In 2007, the U.S. Fish and Wildlife Service’s La Grande Field Office took over responsibility for the monitoring and reporting of the Dry Creek Columbia spotted frog monitoring study. 

Columbia spotted frogs in Dry Creek have been surveyed twice each year since 2001 (via mark-recapture surveys in June and recruitment surveys in August of each year).  In addition, three exclosures were constructed in 2006 to protect important spotted frog habitat. 

Three additional studies have been coordinated with the spotted frog survey work in Dry Creek:  1) Chytrid fungus analysis (June 2005) by US Geological Survey; 2) Genetic research (August 2006) by US Geological Survey; and 3) Fish health by the US Fish and Wildlife Service (August 2006).  However, this report only summarizes the results from the 2007 Dry Creek monitoring project for Columbia spotted frogs. 

Telemetry. Passive Integrated Transponder (PIT) tags are used to track individual frogs.  Each frog is equipped with a unique PIT tag, sexed, weighed, and measured for length along a standard transect.  Surveyors walk the transect three times each year: twice in the spring for a mark-recapture population estimate and once in the late summer for an assessment of breeding success.  Each time a frog is encountered along the transect, it is checked for an existing PIT tag, sexed, weighed, and measured for length to track growth rate and survival.

Reports

2001 Dry Creek Monitoring Report
2002 Dry Creek Monitoring Report
2003 Dry Creek Monitoring Report
2004 Dry Creek Monitoring Report
2005 Dry Creek Monitoring Report
2006 Dry Creek Monitoring Report
2007 Dry Creek Monitoring Report

References

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.

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.

USDI. U.S. Fish and Wildlife Service. 1993. Endangered and threatened wildlife and plants; 12-month finding on petition to list the spotted frog. Federal Register 58:27260-27263. May 7, 1993.