Columbia Spotted Frog

Taxon, Status, and Rank

Species Rana luteiventris Thompson Family Ranidae (True Frogs) Status State Candidate, USFWS Species of Concern State Rank S4 Global Rank G4

General Description

This is a medium to large (adults from 42 mm to 103 mm snout-vent length) aquatic frog. The dorsal color is beige or olive-brown to brick red with black spots that have ragged edges and light centers. In Washington, the undersides of the legs and margin of the abdomen are typically orange 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° 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 an undamaged tail, 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.

Identification Tips

Native True Frogs (Rana species) in Washington have dorsolateral folds (unlike other Washington anurans) and are similar in appearance. The Columbia and Oregon 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 Leopard Frog has well-defined oval and round dark spots with pale borders, conspicuous dorsolateral folds that extend the entire length of the body, and a white underside. The following traits distinguish the Columbia 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), and 6) the dorsolateral folds are interrupted about two-thirds the distance down the back from the eye and often disappear entirely posteriorly. 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 Columbia Spotted Frog from those of the Cascades Frog and Northern Red-legged frog. Larger tadpoles (i.e., > 50 mm total length) of the Columbia 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. The abdominal muscles of Leopard Frogs are relatively transparent resulting in a clear view of the intestines and the dorsal fin is colorless. Bullfrog and Green Frog (an uncommon non-native species) 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 Columbia Spotted Frog and Cascades Frog cannot be easily distinguished. Northern Red-legged Frogs and Leopard 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.

Phenology

Breeding in the Columbia Basin, at elevations near 1800-2000 feet (548-609 m), begins in late March to early April. In the Okanogan Highlands breeding starts in late April to early May at mid-elevation sites between 2000 and 3500 feet (609-1066 m) and late May to early June at elevation sites > 4500 feet (1371 m). Embryos take approximately 3-5 weeks to develop, depending on the temperature regime and elevation. Tadpoles transform in the summer or fall of their first year. Metamorphosis may be delayed at higher elevation sites. Columbia Spotted Frog over-wintering behavior has not been studied in Washington.p>

Range

In Washington, the Columbia Spotted Frog occurs east of the Cascade Mountain crest in the East Cascades, Okanogan, Canadian Rocky Mountain, Columbia Basin, and Blue Mountain Ecoregions, spilling over the Cascade crest to the west slope in the north Cascades near Harts and Rainy Passes. See Distribution Map.

For information on the complete range of this species, see NatureServe Explorer.

Habitat and Habits

This species is relatively aquatic and is rarely found far from water. It occupies a variety of still water habitats and can also be found in streams and creeks. It is common to see these frogs basking on the shore or on floating debris. Breeding habitat is the temporarily flooded margins of wetlands, ponds and lakes. Flooded pools and still water edges of creeks may also be used in some areas. 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 (such as springs and creeks) are most likely necessary for winter survival in areas subject to freezing.

State Status Comments

This species is common in the Okanogan Highlands and the northern Cascade Mountains. Small, scattered populations occur in the shrub-steppe vegetation zones of the Columbia Basin. Due to the decline of its sibling species, the Oregon Spotted Frog, and the decline of Columbia Spotted Frog populations in other states, this species is being monitored in Washington.

Inventory and Research Needs

Information is needed on occurrence and status of populations in the Columbia Basin and the Blue Mountains. Research is needed on the impact that forestry practices, cattle grazing, and non-native species introduction (primarily fish and Bullfrogs) have on spotted frog populations. As Columbia Spotted frogs have also been recorded in off-channel habitats along larger riverine systems, the effects of hydrological changes on off-channel habitats in impounded systems need study.

Threats and Management Concerns

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. Beaver maintain a wetland habitat mosaic that is important for this species; beaver removal may be detrimental. Successional changes in vegetation may also threaten this species, but are unstudied.

References

Corkran and Thoms (1996), Green et al. (1997), Leonard et al. (1993), Nussbaum et al. (1983), Stebbins (1985).

Personal communications: M. Hayes

Hallock, L.A. and McAllister, K.R. 2005. Columbia Spotted Frog. Washington Herp Atlas. http://www1.dnr.wa.gov/nhp/refdesk/herp/