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Oregon spotted frog

Photo of Oregon Spotted Frog (Teal Waterstrat USFWS)

Scientific name: Rana pretiosa 

Status:Threatened 

Critical Habitat: Final

Listing Activity: On August 28, 2014, the USFWS listed the frog as a threatened species under the Endangered Species Act. Critical habitat was designated on May 11, 2016.

Potential Range Map

  • Habitat and Distribution

    The Oregon spotted frog is the most aquatic native frog in the Pacific Northwest and its habitats include lakes, ponds, wetlands and riverine sloughs. It is almost always found in or near a perennial body of water that includes zones of shallow water and abundant emergent or floating aquatic plants, which the frogs use for basking and escape cover.  Large wetland complexes with the following characteristics are likely to host a larger number of frogs than small sites: (1) breeding and overwintering sites are connected by year-round water; (2) water levels of sufficient depth are maintained throughout the period between oviposition and metamorphosis; and (3) absence of introduced predators, especially warm-water game fish and bullfrogs.  Larger wetland habitats with perennial water are more likely to provide an abundance of seasonal microhabitats, hiding cover from predators and food for frogs.  Oregon spotted frogs that reside in small habitats without connectivity to perennial water are more vulnerable to extirpation.

    The Oregon spotted frog has been lost from at least 78 percent of its former range.  This species has been documented in British Columbia, Washington, Oregon, and California, although it is believed to have been extirpated (locally extinct) from California. It is currently known to occur from extreme southwestern British Columbia, south through the eastern side of the Puget Trough and in the Cascades Range from south-central Washington at least to Klamath Basin in southern Oregon.

    In Oregon, this frog species is only known to occur in Wasco, Deschutes, Klamath, Jackson and Lane counties, although historically they were also found in Multnomah, Clackamas, Marion, Linn, and Benton counties. Oregon spotted frogs occur primarily on lands managed by the US Forest Service, US Bureau of Land Management, US Fish and Wildlife Service and private lands in Oregon.  The species distribution in Oregon is generally within the eastern Cascades and Klamath Basin.  Oregon spotted frog distribution west of the Cascade Mountains in Oregon is restricted to a few lakes in the upper watersheds of the McKenzie River and Middle Fork Willamette River sub-basins.

    To see the entire range of the Oregon spotted frog, click here for the Complete Profile (ECOS)

     

    Description

    The Oregon spotted frog is named for the black spots that cover the head, back, sides, and legs. The dark spots have ragged edges and light centers, which are usually associated with tubercles or raised areas of skin; these spots become larger and darker and the edges become more ragged with age. Body color also varies with age. Juveniles are usually brown or, occasionally, olive green on the back and white or cream with reddish pigments on the underlegs and abdomen. Adults range from brown to reddish brown, but tend to become more red with age; large, presumably older individuals may be brick red over most of the back. Red increases on the abdomen with age, and the underlegs become a vivid orange-red. This red coloration can be used to distinguish the spotted frogs from other native frogs.

    The Oregon spotted frog is a medium-sized frog, ranging from 44 to 100 millimeters (1.74 to 4 inches) in body length. Females are typically larger than males and can reach up to 100 millimeters (4 inches).

     

    Life History

    This species typically begins to breed at three years of age. In Oregon, breeding occurs as early as mid-March at lower elevations and between early April and early June at higher elevations. Females may deposit egg masses at the same location in successive years in shallow, often temporary, pools no more than six inches deep. Eggs usually hatch within three weeks after oviposition. Tadpoles are grazers, having rough tooth rows for scraping plant surfaces and ingesting plant tissue and bacteria. They also consume algae, detritus, and probably carrion.  Tadpoles then metamorphose into froglets during their first summer.  Post-metamorphic Oregon spotted frogs feed on live animals, primarily insects.

    Oregon spotted frogs require winter habitat that retains oxygenated water with sheltering locations where they are protected from predators and freezing.  Overwintering may occur in flowing systems such as springs and creeks (typically slow flowing) or in still-water systems such as beaver complexes, riverine oxbows, lakes and ponds.  The frogs have been observed to be active under ice.  In severe cold winter conditions, Oregon spotted frogs are susceptible to mortality from freezing or hypoxia in shallow aquatic habitats that freeze to the substrate.

     

    Reasons for Decline

    Many factors are believed to have caused Oregon spotted frogs to decline and continue to threaten this species, including loss of habitat, non-native plant invasions, and the introduction of exotic predators such as bullfrogs. Over 95 percent of historic marsh habitat, and consequently Oregon spotted frog habitat, has been lost in the Willamette and Klamath basins. Changes in hydrology (due to construction of ditches and dams) and water quality, development, and livestock overgrazing continue to result in habitat loss, alteration, and/or fragmentation. Non-native plant invasions by such aggressive species as reed canarygrass (Phalaris arundinacea), and succession of plant communities from marsh to meadow also threaten this species' existence. Introductions of bullfrogs and non-native fishes have affected this species both directly, by eating them, and indirectly, by outcompeting or displacing them from their habitat.

    The majority of Oregon spotted frog populations are small and isolated. These factors make the Oregon spotted frog more vulnerable than large connected populations to random, naturally occurring events, such as drought, disease, and predation.

    Conservation Measures

    Oregon spotted frog conservation is largely focused on restoring and improving the quality of aquatic habitats and reducing threats posed to the frog from invasive plants and animals.  Conservation efforts will focus on improving hydrological function and connectivity within and between spotted frog habitats and reducing the threat of invasive species such as bullfrogs and reed canarygrass through active management. Riverine and wetland restoration projects are underway on public and private lands in Oregon to improve habitat quality for Oregon spotted frogs.  An important component to several of these projects involves promoting and enhancing beaver populations and activity.  Bull frog removal efforts also are being implemented within spotted frog habitat on private and Federal lands.

    References and Links

    US Fish and Wildlife Service. "Endangered and threatened wildlife and plants; Threatened status for Oregon Spotted Frog, final rule." Federal Register 79.168 (2014): 51657-51710.

    Corkran, C.C. and C.R. Thoms. 1996. Amphibians of Oregon, Washington, and British Columbia: A field identification guide. Lone Pine Publishing, Edmonton, Alberta. 175 pp.

    Hayes, M.P. 1994. The spotted frog (Rana pretiosa) in western Oregon. Part I. Background. Part II. Current status. Oregon Department of Fish and Wildlife Tech. Rept. #94–1–01. Unpublished Report.

    Leonard, W.P., H.A. Brown, L.L.C. Jones, K.R. McAllister, and R.M. Storm. 1993. Amphibians of Washington and Oregon.

     

     

    Last updated:  March 11, 2020

     

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