Rana pretiosa

This frog has upturned eyes, usually small bumps and tubercles on the the back and sides, and short hind legs relative to body length, and hind feet that are fully webbed (Leonard et al. 1993). The head is marked with a faint mask, and a light jaw stripe extends to the shoulder. Black spots are scattered on the head, back, sides, and legs. The dark spots have ragged edges and light centers and usually are associated with a tubercle or raised area of skin. The spots become larger and darker, and the edges become more ragged, with age (Hayes 1994). Juveniles are usually brown or, occasionally, olive green on the back and white, cream, or flesh-colored with reddish pigments on the underlegs and abdomen (McAllister and Leonard 1997). Adults range from brown to reddish brown but tend to become redder with age. Large, presumably older, individuals may be brick red over most of the dorsal surface (McAllister and Leonard 1997). Red surface pigment on the adult abdomen increases with age, and the underlegs of adults are a vivid orange red. Tan to orange folds along the sides of the back (dorsolateral folds) extend from behind the eye to midway along the back (McAllister and Leonard 1997). This is a medium-sized frog about 44-105 millimeters (1.7 to 4.1 inches) in body (snout-vent) length (McAllister and Leonard 1997, Rombough et al. 2006). Adult females are typically larger than adult males (the latter reach only about 75 mm (3 inches) (Leonard et al. 1993).

The weak call consists of a rapid series of 6-9 low clucking notes, sometimes described as sounding like a distant woodpecker's tapping. This species generally vocalizes only during the breeding season (Leonard et al. 1993); however vocalizations have been heard during the fall (Leonard et al. 1997).

"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." Source: Hallock and McAllister (2005). Corkran and Thoms (2006) also distinguished this species from the northern red-legged frog and Cascades frog

Corkran and Thoms (2006) presented keys to eggs, larvae, and metamorphosed individuals.

The Oregon spotted frog is highly aquatic and generally avoids dry uplands. It is rarely found far from permanent quiet water. Usually it occurs in vegetated shallows or among grasses or sedges along the margins of streams, lakes, ponds (including those behind beaver dams), oxbows, springs, and marshes (Hodge 1976, Licht 1986, Watson et al. 2003, Chelgren et al. 2008). Individuals move among seasonal habitats usually along flooded or saturated corridors (Watson et al. 2003). In Washington, overland movements were very rare (Watson et al. 2003). Breeding occurs usually in shallow water in pools, ponds, or other quiet waters, among moderate or dense herbaceous vegetation, often close to shore but sometimes far from away from the edge (Pearl et al. 2009). Oviposition sites may be devoid of water later in the year. In Washington, frogs used deeper permanent pools in the dry season; in the coldest periods they buried themselves at the base of dense vegetation in shallow water under ice (Watson et al. 2003). In central Oregon, breeding habitats were natural or anthropogenic and ranged from small, seasonally flooded oxbow ponds to larger channels and marshes within an extensive wetland complex; most sites had extensive emergent and submergent vegetation (Bowerman and Pearl 2010). Wintering sites are in springs, slow-flowing channels, or deep open water (Hallock and Pearson 2001, Chelgren et al. 2008).

Pearl and Hayes (2004) reviewed available literature and summarized habitat relationships as follows. Oregon spotted frogs are generally associated with wetland complexes > 4 ha in size with extensive emergent marsh coverage that warms substantially during seasons when the frogs are active at the surface. The expanse of inundation in wetlands often varies greatly between spring and fall, but sites always include some permanent water adjacent to seasonally inundated habitat. Field observations and recent telemetry data suggest the frog utilize different wetland microhabitats for breeding, the nonbreeding active season (summer and portions of spring and fall), and overwintering. Breeding sites are generally associated with seasonally flooded, shallowly sloping benches that are vegetated with the previous year's emergent vegetation and are relatively unshaded. The frogs' shallow-water breeding habitat may contribute to relatively frequent stranding of the communally deposited egg masses and substantial egg mortality. Limited data suggest that adults may move little during the nonbreeding active season and may prefer microhabitats of moderate vegetation density that are near aquatic refuges.

The life cycle involves distinct stages: eggs, larvae, and metamorphosed individuals. Breeding occurs as early as February or March at lower elevations and as late as late May or early June at higher elevations (Leonard et al. 1993), and at a particular elevation southern populations likely tend to breed earlier than do northern populations. Breeding occurs in February at sea level in British Columbia. In central Oregon, the period from first oviposition to first hatching occurred in mid- to late April (Bowerman and Pearl 2010). Where freezing occurs, breeding generally occurs as early as winter thaw permits. In at least some areas breeding is "explosive" and occurs primarily within a period of 1-2 weeks (Pearl and Hayes 2005). Reproductive females likely breed once each year and deposit one egg mass per breeding event, and they usually lay eggs communally in clusters containing up to several hundred egg masses, often in the same location year after year. Eggs survive freezing air temperatures and ice cover for up to several days (Bowerman and Pearl 2010), hatch in 3-21 days, depending on temperature. Metamorphosis occurs in mid- to late summer (Nussbaum et al. 1983). Individuals first breed when 1-3 years old (females generally at 2-3 years), depending on the elevation and latitude (mature at greater age at high elevations). Most individuals live not more than a few years, but some may live more than a deacde (see USFWS 2009).