Cascades frog (Rana cascadae)

KingdomAnimalia
PhylumChordata
ClassAmphibia
OrderAnura
FamilyRanidae
GenusRana (1)
SizeMale length: up to 6.7 cm (2)
Female length: up to 8.1 cm (2)
Male weight: up to 28 g (2)
Female weight: up to 56 g (2)

The Cascades frog is classified as Near Threatened (NT) on the IUCN Red List (1).

A mountain-dwelling amphibian (3), the Cascades frog (Rana cascadae) is a medium-sized, slender species (2) (4) (5) which is named after the Cascades Mountain range in the western United States where it was first found (4). 

The Cascades frog is generally mottled tan, brown, olive-green or olive-brown, with well-defined, inky black spots on the back. It is yellowish on the underside and on the back of the legs, with black, cream and greenish-yellow mottling on the groin, and cream along the side of the body (3) (4). Some individuals may also have a small amount of red pigmentation on the underside of the body (3). The Cascades frog also has a dark face mask, with a lighter stripe across the upper jaw which extends back towards the shoulder (2) (4) (5).

This species has two distinct parallel ridges of skin, called ‘dorsolateral folds’, which run along the back of the body, long legs, and only a small amount of webbing between the toes (3) (4). Male Cascade frogs may also have swollen grey pads, called nuptial pads, on the thumbs (3).

The tadpoles of the Cascades frog have an oval body and a pointed tail. They are dark brown to black, developing a metallic silvery or brassy pigmentation as they grow. The juvenile Cascades frog resembles the adult but lacks the yellow colouration on the underside of the body (3).

The Cascades frog produces a faint series of low, grating, clucking noises, and weak, slow, low croaks or chuckles (3) (4).

The Cascades frog occurs in the Cascades Mountains in the western United States, ranging from northern Washington south through Oregon to northern California. Populations also occur in the Olympic Mountains, Washington, and in the northern Sierra Nevada Mountains, Mount Shasta, Lassen Peak, the Marble Mountains and the Trinity Alps in California (1) (2) (4) (6) (7).

This species generally occurs at elevations between 665 and 2,450 metres, although some Washington populations may occur at lower altitudes (1) (4).

The Cascades frog inhabits a variety of wet mountain habitats, such as meadows, sphagnum bogs and marshy areas, as well as pools, ponds, lakes, and streams in open coniferous forests (1) (2) (4) (6).

This species breeds in still water bodies such as wetlands, ponds and lakes, which may be permanent or persist for at least two months after the snow has melted (3). Breeding habitats are also typically free of predatory fish (4). The Cascades frog hibernates in muddy substrate at the bottom of ponds or in wet ground (1) (4).

The diet of the Cascades frog is poorly known, but adults are likely to consume a wide variety of invertebrates. Other frogs may also be taken (4) (6).

The Cascades frog spends the winter in hibernation, generally not far from breeding sites. It becomes active as the ice thaws, which happens between March and August depending on location, with breeding beginning soon after it emerges (3) (4) (6). Adult Cascade frogs breed only once during the year, typically returning to the same location to breed (2) (4) (7). Although male Cascade frogs are not considered territorial, they often behave aggressively during the short breeding season (4) (6).

During spawning, a mass of eggs is deposited in shallow water, usually over soft or silty substrate (2) (4) (7). The water temperature strongly influences the rate of egg development, but hatching usually occurs within two to four weeks (6). The tadpoles are speckled with dark spots, and grow up to five and a half centimetres in length (4). The larval period generally lasts up to two months, with tadpoles metamorphosing by late summer (2) (3) (4) (6).

Although currently only classified as Near Threatened on the IUCN Red List of Threatened Species, the Cascades frog population is thought to be in decline in many parts of its range (1). The Cascades frog is no longer present in approximately 50 percent of its historical range in California, and the numbers in remaining populations have been severely reduced (4). Several threats to this species have been identified, including the presence of non-native predatory fish, the gradual loss of open meadows due to fire suppression, and the loss of aquatic breeding habitat due to drought (1) (4) (6).

Pesticides and fertilisers may also have contributed to declining populations in California, while nitrites may affect the behaviour and metamorphosis of Cascade frog larvae (6). The eggs of the Cascades frog are also highly susceptible to the pathogenic fungus Saprolegnia ferax (1) (4).

Perhaps the biggest growing threat to amphibian populations is climate change. This has been demonstrated to affect the breeding activity of some species, which could eventually lead to changes in population structure. Changing temperatures may disrupt timing of breeding, periods of hibernation and the ability of some amphibian species to find food (8).

In addition, climate change may lead to increased spread of infectious disease, while changes in precipitation, acidification, pollutants, and increased UV radiation may also affect the immune system of amphibians (8).

Some populations of the Cascades frog are found within national parks and wilderness areas, such as Crater Lake National Park and the Three Sisters wilderness area in Oregon, Olympic and Mount Rainier National Parks in Washington, and Mount Lassen and Trinity Alps in California (1). This frog is listed as a California Species of Special Concern (2) (6).

Find out more about the Cascades frog:

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This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
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  1. IUCN Red List (May, 2011)
    http://www.iucnredlist.org/
  2. Garwood, J.M. and Welsh, H.H. Jr. (2007) Ecology of the Cascades frog (Rana cascadae) and interactions with garter snakes and non-native trout in the Trinity Alps Wilderness, California. Final report prepared for the California Department of Fish and Game and the National Fish and Wildlife Foundation. Arcata, California.
  3. Hallock, L.A. and McAllister, K.R. (2009) Washington Herp Atlas - Cascades Frog. Washington State Department of Natural Resources. Available at:
    http://www1.dnr.wa.gov/nhp/refdesk/herp/
  4. CaliforniaHerps: A Guide to the Amphibians and Reptiles of California - Cascades frog (May, 2011)
    http://www.californiaherps.com/frogs/pages/r.cascadae.html
  5. U.S. Geological Survey: Checklist of Amphibian Species and Identification Guide - Cascades frog (May, 2011)
    http://www.npwrc.usgs.gov/resource/herps/amphibid/species/rcascade.htm
  6. AmphibiaWeb - Cascades frog (May, 2011)
    http://amphibiaweb.org/cgi/amphib_query?where-genus=Rana&where-species=cascadae
  7. Garwood, J.M. (2009) Spatial Ecology of the Cascades Frog: Identifying Dispersal, Migration and Resource Uses at Multiple Spatial Scales. MSc Thesis, Humboldt State University.
  8. Blaustein, A.R., Belden, L.K., Olson, D.H., Green, D.M., Root, T.L. and Kiesecker, J.M. (2001) Amphibian breeding and climate change. Conservation Biology, 15(6): 1804-1809.