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Oregon Spotted Frogs

Oregon Spotted FrogOregon spotted frogs are seldom seen, but your best opportunity is in the summer when the frogs are busy doing froggy things.

The Oregon spotted frog (Rana pretiosa) endemic to the Pacific Northwest. Historically, it ranged from southwestern British Columbia south to the northeast corner of California. In Washington, the Oregon spotted frog was historically found in the Puget Trough from the Canadian border to the Columbia River and east into the southern Washington Cascades.

Oregon spotted frogs breed in late winter or early spring. Females lay their eggs in communal oviposition sites; areas of shallow, still or slow-moving water and sparse, emergent wetland vegetation. Eggs hatch in 18 to 30 days, and the tadpoles grow and develop for 13 to 16 weeks prior to metamorphosis in mid-summer. Oregon spotted frogs mature and begin breeding at two or three years of age.

Oregon spotted frogs are almost entirely aquatic in habit, leaving the wetlands only occasionally and for short duration. Wetlands associated with lakes, ponds and slow-moving streams provide suitable habitat. However, these aquatic environments must include a shallow emergent wetland component to be capable of supporting an Oregon spotted frog population. Historically, this critical element was found in the floodplains of many larger water bodies. Various emergent wetland and floating aquatic plants are found in abundance in Oregon spotted frog habitat. Adult female and juvenile frogs, in particular, spend summers in relatively warm water of this shallow emergent wetland environment.

Within Washington, Oregon spotted frog populations face a myriad of threats. Historically, the shallow floodplain pools that Oregon spotted frogs inhabited were drained, diked and filled to accommodate human needs. Exotic plants like reed canarygrass have changed the character of many wetlands and reduced their value as habitat for Oregon spotted frogs. Oregon spotted frogs are preyed upon during all life stages by a wide variety of predators, ranging from invertebrates that prey on eggs, to garter snakes and herons that feed on adults. Among the most significant of predators are various introduced species, most notably the numerous warmwater fish species (primarily sunfishes, bass, perch, walleye and catfishes) introduced for sport fishing and the bullfrog. Because of their life histories and habitat affinities, these introduced species pose serious threats to Oregon spotted frog populations. Based on an assessment of presence at historical localities, the species is estimated to have been lost from 78% of its former range. However, considering the broad former range suggested by the historic data, it is likely the species has actually been lost from over 90% of its former range.

The historic locations for populations in Washington have been verified using museum specimen and published records. There are around 12 known populations remaining in Washington. An additional 20 extant populations are known in Oregon and one in British Columbia. Due to the limited number of extant populations and the inadequacy of existing protection for these populations, the state of Washington has recommended that the Oregon spotted frog be listed as a state endangered species. Likewise, the FWS is also evaluating listing the species as threatened or endangered in 2013.

Page Photo Credits — Oregon Spotted Frog - Gary Nafis
Last Updated: Apr 08, 2013
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