|<<Back to Northwest HerpsThe Oregon spotted frog is a candidate for listing under the Endangered Species Act.
It has been documented that the Oregon Spotted Frog has lost at least 78 percent of its former habitat range. However, not much solid data is provided, it is documented that the species has been known to occur in the following regions of Washington, Oregon and California. Currently the Oregon Spotted Frog seems to have been exterminated from California.
The Spotted Frog can be found in the southwestern most parts of British Columbia, and from the eastern side of the Puget/Willamette Valley Trough and into the Columbia River Gorge Oregon and Southern Washington. The Oregon Spotted Frog habitat historically covers Clackamas, Linn, Klamath, Multnomah, Wasco, and Benton counties. Today the species has only been found to occur in the Deschutes, Klamath, and Lane counties.
Oregon Spotted Frog is an aquatic species found near recurrent bodies of water. The Spotted Frog can be found in the shallows typically and prefers areas that provide abundant floating aquatic plants. (Leonard et al. 1993, Corkran and Thoms 1996, McAllister and Leonard 1997, Pearl 1997, Pearl 1999).
The Oregon Spotted Frogs habitats are identified by:
- Overwintering, Breeding sites are related by year-round water.
- Reliable water levels that maintain depth between times of laying eggs (oviposition) and species development (metamorphosis)
- Absence of predators, especially warm-water game fish and bullfrogs
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 44-100 mm (1.74-4 in) in body length (McAllister and Leonard 1997). Females are typically larger than males and can reach up to 100 mm (4 in) (Leonard et al. 1993).
This species begins to breed at three years of age. Breeding occurs in February or March at lower elevations and in late May or 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 6 inches deep. Eggs usually hatch within 3 weeks after oviposition. Tadpoles are grazer, having rough tooth rows for scraping plant surfaces and ingesting plant tissue and bacteria. They also consume algae, detritus, and probably carrion (Licht 1974, McAllister and Leonard 1997). Tadpoles then metamorphose into froglets during their first summer (Leonard et al. 1993). Post-metamorphic Oregon spotted frogs feed on live animals, primarily insects.
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% 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.
Efforts are being made to eliminate and to prevent future introductions of bullfrogs and warm-water game fish from spotted frog habitat. Active management is also required to control non-native plant species like reed canarygrass. Protecting Oregon spotted frog populations through maintaining healthy aquatic habitats will continue to be the key objective of land managers.
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.
Oregon Fish & Wildlife Office 2002.
Published online by Herpetology Northwest Copyright 2003
|Size: 1.74-4 inches
Regions: Puget/Willamette Valley, Oregon through the Columbia River Gorge of Southern Washington and Oregon.
Breeding: Breeding occurs in February or March at lower elevations and in late May or early June at higher elevations.
Alerts: The Oregon spotted frog is a candidate for listing under the Endangered Species Act