Overview
The Oregon Spotted Frog (Rana pretiosa) is the most aquatic native frog in the Pacific Northwest, spending virtually its entire adult life immersed in perennial, shallow marshlands. Characterized by its upturned eyes, dark irregular spots with light centers, and incandescent salmon-red to bright orange wash across its underbelly and legs, it is a flagship specialist of intact river valley wetlands.
Biology and Physical Characteristics
Rana pretiosa has a medium-sized, stout body with fully webbed hind feet designed for powerful aquatic propulsion. Its dorsal skin is reddish-brown, olive-tan, or green, covered in ragged, dark brown spots with fuzzy borders. Its eyes are positioned high on its head and angled upward, allowing it to rest half-submerged in duckweed with only its eyes and nostrils above water. The undersides of its thighs and lower belly are suffused with vivid reddish-orange pigment.
Behavior and Ecology
An obligate marsh dweller, the Oregon Spotted Frog requires warm, extremely shallow water (less than 10 cm deep) with abundant emergent vegetation for breeding. In late winter, adults congregate to lay communal egg masses in sun-warmed, flooded sedge shallows. In winter, they hibernate underwater, burying themselves in soft silty mud or resting beneath submerged undercut banks where flowing springs prevent freezing.
Conservation and Human Impact
Classified as Vulnerable by the IUCN and federally protected as Threatened under the US Endangered Species Act, the Oregon Spotted Frog has suffered catastrophic habitat losses exceeding 90% of its historic range due to wetland drainage for agriculture, altered hydrology from river diking, and heavy predation by invasive American bullfrogs.
Interesting Factoid
The Oregon Spotted Frog’s eyes are tilted directly upward toward the sky; this unique periscope design allows it to float hidden under floating pond duckweed while watching for passing dragonfly meals above.