| Species | Rana pretiosa Baird and Girard |
| Family | Ranidae (True Frogs) |
| Status | State Endangered Species, USFWS Candidate |
| State Rank | S1 |
| Global Rank | G2 |
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This is a medium to large (adults from 48 mm to 103 mm snout-vent length) aquatic frog. The dorsal color is olive-brown to brick red with black spots that have ragged edges and light centers. The undersides of the legs and margin of the abdomen are orange-red to red (absent in newly metamorphosed frogs and small juveniles). The legs are relatively short and the toes are nearly fully webbed. The eyes are oriented upward laterally at roughly a 45-degree angle. Breeding males develop large forelimbs and thumb bases and have a dark nuptial pad on each thumb. The call is a series of six to nine low-pitched clucks similar to the sound made when the tongue is clicked against the roof of the mouth. One must typically be within 5 m to hear this faint call.
The tadpole has an oval body with dorsal eyes, a vent on the right side, a spiracle on the left side and a dorsal fin that originates on the body near the dorsal tail-body junction. The tip of the tail is pointed. At hatching, the tadpoles appear black, have long tails (> 1.5 times body length), obvious gills and remain associated with the egg mass for days. As the tadpoles grow, the ground color and belly lighten and silver flecks appear, eventually covering the gut. Tadpoles can grow to large sizes (110 mm total length) before metamorphosis. Larger tadpoles, with undamaged tails, have a tail length to body length ratio of over 2.6.
Individual egg masses are globular, loose to the touch, grapefruit-sized and not attached to a vegetation brace, although they may stick to the vegetation under the egg masses. The eggs and larvae appear black (but are actually dark brown). The frogs lay the egg masses at water body margins in water usually less than 15 cm deep. The top of the egg mass is often exposed at the water surface. Egg masses are typically communally laid, resulting in clustered egg mass groups of two to more than 100. Single egg masses in the vicinity of multi-mass clusters are common. See Photos Page.
Native True Frogs (Rana species) in Washington have dorsolateral folds (unlike other Washington anurans) and are similar in appearance. The Oregon and Columbia Spotted Frog species have subtle color variations, but are morphologically indistinct (they were distinguished as separate species by genetic analysis) and may be separated by geographic locality. The following traits distinguish the Oregon Spotted Frog from the Cascades and Northern Red-legged Frog: 1) the dorsal spots are black with ragged edges and light centers, 2) the eyes are oriented upward with the entire pupil of both eyes visible when the frog is viewed directly from above, 3) there is nearly full webbing between the toes with the webbing of the hind foot reaching almost to the tip of the longest toe and the webbing is almost straight when the toes are stretched apart, 4) the coloration in the groin area is similar to the coloration anteriorly on the side and posteriorly on the thighs with no obvious yellow and black mottled patch or patches, 5) when the hind leg is pressed forward against the body, the heel of the hind foot will seldom reach the nostril (similarly, the knee to heel measurement is typically less than half of the snout-vent length), 6) the dorsolateral folds are interrupted about two-thirds the distance down the back from the eye and often disappear entirely posteriorly, and 7) Cascade Frogs have honey-colored and yellow undersides, not red. The above traits may be difficult to see or absent in small juvenile frogs. Bullfrogs, a common non-native species, have a distinct fold from the posterior edge of the eye, around the top of the tympanum and ending at the arm and they lack dorsolateral folds.
In general, it is difficult to distinguish the tadpoles of the Oregon Spotted Frog from those of the Cascades Frog and Northern Red-legged frog. Larger tadpoles (i.e, > 50 mm total length) of the Oregon Spotted Frog have a tail length to body length ratio of 2.7 whereas Cascades Frog and Northern Red-legged Frog have a tail length to body length ratio 2.6 or smaller. This criterion can only be used if the tail is undamaged. Bullfrog and Green Frog tadpoles are also similar but larger tadpoles have distinct black spots over a typically khaki-colored body and tail and the abdomen is opaque and lacks pigments with a metallic quality.
The communal egg masses of the Oregon Spotted Frog and Cascades Frog cannot be easily distinguished. Northern Red-legged Frogs do not lay egg masses in communal overlapping clusters, although they may be closely spaced if the vegetation braces to which the egg masses are attached are close together; rather they attach egg masses to vegetation individually in water that is usually over 25 cm deep. The Northwestern Salamander has a grapefruit-sized globular egg mass, but its jelly is solid to the touch, always attached to vegetation or woody debris and the eggs and larvae are brown not black. No other species that occur in the same range and habitat have large globular egg masses. See Key Features Page.
Breeding in Thurston County starts at the end of February or very early March at elevations less than 100 feet (30 m). Breeding in Klickitat County starts in early to mid-March at elevations of 1800-1950 feet (549-594 m). Embryos take approximately three weeks to develop to hatching. Tadpoles transform in mid-summer to early fall of their first year. Recent telemetry studies of three Washington populations revealed that the frogs move underwater throughout the winter months though surface activity diminishes or ceases entirely.
The historical range in Washington is the Puget Trough Ecoregion and the southern extent of the Eastern Cascades Ecoregion. Only six populations are known, four in Thurston County and two in Klickitat County. See Distribution Map.
In Thurston County, the upper Black River population has been split into 3 separate and distinct populations. Funnel trapping and habitat assessments in areas separating known breeding sites determined that movements of frogs between sites was likely rare, at best.
For information on the complete range of this species, see NatureServe Explorer.
This species is highly aquatic and is rarely found away from water. Extant populations occur in large shallow wetland systems associated with a stream or stream network. Breeding habitat is in seasonally flooded margins of wetlands. Egg masses are placed in areas where they receive little or no shading from vegetation. Waters that remain aerobic and do not freeze to the sediments are necessary for winter survival in areas subject to freezing. Beaver impounded systems appear to provide many of the habitat requirements of this species.
This species has declined dramatically from it original distribution due to filling and alteration of wetlands. The six remaining populations are isolated and vulnerable to a wide variety of factors that might interfere with reproduction or survival.
All sightings of this species should be reported to the Washington Department of Fish and Wildlife. Surveys for additional populations, especially in Skagit, Snohomish and Whatcom counties, are needed. Development of predictive models based on the soils associated with historic and extant populations would greatly enhance inventory abilities.
Human induced changes in hydrology, water quality and wetland integrity are the major threat to this species. Nonnative fish and Bullfrogs are also a potential threat to this species. Loss of early successional wetland habitat to shrub scrub wetlands is a potentially detrimental pattern that needs further investigation. Beaver maintain a wetland habitat mosaic that is important for this species; beaver removal may be detrimental.
Breeding season mark and recapture efforts at Dempsey Creek, in Thurston County, will enter their ninth year in 2005. This population monitoring effort seeks to gather population data over a ten-year span, ending in 2006. To better assess population sizes and frog movements, additional trapping and marking is planned for other upper Black River populations in 2005. The majority of frogs are captured in aquatic funnel traps. Marking is done using passive integrate transponders (PIT tags). This work is conducted by WDFW (Kelly McAllister).
Annual egg mass counts are conducted at the two Oregon Spotted Frog populations in Klickitat County. The US Fish and Wildlife Service (Joe Engler) and WDFW (Marc Hayes) are the lead agencies for the Conboy National Wildlife Refuge egg mass counts. The Natural Heritage Program (DNR - Lisa Hallock) organizes the annual egg mass count at Trout Lake Natural Area in cooperation with the Natural Areas Program (DNR - David Wilderman) and WDFW (David Anderson).
Corkran and Thoms (1996), Green et al. (1997), Hallock and Pearson (2001), Hayes et al. (2000), Hayes et al. (2001), Leonard et al. (1993), Lewis et al. (2001), Licht (1969), McAllister and Leonard (1997), McAllister and White (2001), Nussbaum et al. (1993), Risenhoover et. al. (2001a, 2001b), Stebbins (1985).
Personal communications: Marc Hayes
Hallock, L.A. and McAllister, K.R. 2005. Oregon Spotted Frog. Washington Herp Atlas. http://www1.dnr.wa.gov/nhp/refdesk/herp/
Last updated: February 2005