Field Office Dry Creek Columbia Spotted Frog Monitoring
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.
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.
Fig. 5 Columbia spotted frog mark-recapture
and recruitment survey location.
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
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. However, due to the high-flow events that moved through the survey area in 2011, all three exclosures are now in non-functional condition.
Fig. 6 Columbia spotted
frog age class and gender totals for 2001-2011 surveys along
Dry Creek, Malheur County, Oregon.
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
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.
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.