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BC Conservation Data Centre: Species Summary


Rana aurora
Northern Red-legged Frog


 
Scientific Name: Rana aurora Baird and Girard, 1852
English Name: Northern Red-legged Frog
English Name Synonyms: Red-legged Frog
 
Classification / Taxonomy
Scientific Name - Concept Reference: Collins, J. T. 1990. Standard common and current scientific names for North American amphibians and reptiles. 3rd ed. Society for the Study of Amphibians and Reptiles. Herpetological Circular No. 19. 41 pp.
Classification Level: Species
Species Group: Vertebrate Animal
Species Code: A-RAAU
Kingdom Phylum Class Order Family
Animalia Craniata Amphibia Anura Ranidae
   
Conservation Status / Legal Designation
Global Status: G4 (May 2015)
Provincial Status: S3 (Mar 2022)
BC List: Blue
Provincial FRPA list: Y (May 2004)  
Provincial Wildlife Act:
COSEWIC Status: Special Concern (May 2015)
SARA Schedule: 1  -  Special Concern (Jan 2005)
General Status Canada: 3 - Sensitive (2005)
   
Ecology & Life History
General Description: Dorsum brown, gray, olive, or reddish, with irregular dark spotting or blotching; usually has a dark mask above the whitish jaw stripe; adults usually red on lower abdomen and underside of legs; usually coarse blackish, red, and yellow mottling in groin; relatively long legs (heel reaches at least to nostril when extended leg is pulled forward; eyes face outward, well covered by lids when viewed from above; prominent dorsolateral folds; snout-vent length usually 4-13 cm; young may have yellow instead of red on underside of legs and in groin; adult males have enlarged forelimbs and thumb base and more extensive webbing (Stebbins 1985).
Subspecies Comments: There is only one subspecies in BC, the Northern Red-legged Frog (R. a. aurora).
Identification Comments: Adults: A mid-sized frog with long hind legs and webbed feet. Adults reach 50-60 mm snout-to-vent length (SVL), and they have two dorsolateral folds running down the length of the back. Colouration consists of a tan to brown dorsal surface with irregular dark spots, a tan or cream coloured throat with back specks, and the characteristic red colouration with mottling in the groin area (young may lack the red colouration). Obvious dark mask above the white lip line. Eyes face more to the side than forward. Tadpoles: tan or olive coloured with gold specks, approximately 70 - 80 mm total length prior to metamorphosis; eyes in from the margins of the head; tall, short tail fin. Eggs: Large, gelatinous, grapefruit- to cantaloupe-sized mass that can become loose, floating, and frothy in appearance near hatching (Ovaska and Sopuck 2004).
Global Reproduction Comments: Breeding time varies geographically; breeds March-July in the north. Breeding period lasts about 1-2 weeks. Eggs hatch in 5-7 weeks in western Oregon. Larvae metamorphose in about 11-20 weeks, but sometimes may overwinter. Larvae in British Columbia metamorphosed in 11-14 weeks.
Provincial Reproduction Comments: Red-legged Frogs reach sexual maturity at 3+ years of age (Licht 1974). Red-legged Frogs are explosive breeders, with reproduction occuring for only a short period in early spring (e.g., 2-4 weeks). Males emit an advertisement call under water that may not be audible to the human ear at the surface (Licht 1969). Males amplex the female and there is external fertilization. Females breed every year, laying their grapefruit- to canteloupe-sized egg mass below the water surface in the littoral zone (30-90 cm), often amongst emergent vegetation (Licht 1969). Like other amphibians, Red-legged Frogs exhibit site fidelity to natal breeding ponds, and females may lay their eggs in the same locations within a breeding site each year. Females lay an average of 530-680 eggs per clutch, which usually hatch within 1 to 1.5 months depending on water temperature; the larval period is relatively long compared to other anurans, lasting 2.5 to 3.5 months (Licht 1969; Calef 1973; Licht 1974). Red-legged Frogs do not exhibit parental care.
Provincial Ecology Comments: Red-legged Frogs can make extensive movements between overwintering areas, breeding sites, and summer foraging areas; dispersal distances are unknown (Ovaska and Sopuck 2004). Red-legged Frogs reach sexual maturity in 3 or more years (Licht 1974); life expectancy of adults in the wild is unknown, but an individual in captivity lived to 15 years (McTaggart Cowan 1941). Like all amphibians, Red-legged Frog populations likely fluctuate extensively from year to year in response to climate (e.g., snowfall or precipitation), with the greatest mortality rates occuring at the tadpole stage (Calef 1973; Licht 1974). A variety of organisms prey on Red-legged Frog tadpoles, including other amphibians, fish, snakes, birds, and aquatic invertebrates (e.g., Odonata larvae). Adult Red-legged Frogs also fall prey to various reptiles, birds and mammals. Garter snakes can quickly eliminate tadpoles from small, temporay ponds (E. Wind, pers. comm.). Red-legged Frogs are susceptible to predation and competition from non-native species such as Bullfrogs and fish (Ovaska and Sopuck 2004; Wind, in review). Habitat degradation, loss (e.g. wetland), and fragmentation are major factors affecting Red-legged Frogs within their native BC range (Ovaska and Sopuck 2004).
Migration Characteristics:
(Global / Provincial)		 
    Nonmigrant:
    Local Migrant:
    Distant Migrant:
    Within Borders Migrant: 		Y / N
N / Y
N / N
na / N
Global Migration Comments: In Oregon, Hayes et al. (2001) found that four individuals moved 1.1, 1.2, 1.3, and 2.4 km between capture points (these were the largest documented movements).
Provincial Mobility & Migration Comments: Like many other amphibians, Red-legged Frogs migrate between aquatic breeding sites, upland summer foraging areas, and overwintering areas during the active season (i.e., late winter-fall). Radio-telemetry studies in Washington and Oregon have demonstrated that adults may move hundreds to thousands of metres between overwintering areas, summer foraging sites, and breeding areas (Hayes et al. 2001; Shean 2002). The majority of individuals may move less in summer within smaller home ranges, but occasional long distance movements take place. Like other amphibian species, Red-legged Frogs have demonstrated site fidelity to breeding and summer foraging areas (Ovaska and Sopuck 2004). In uncut forest on northern Vancouver Island, Red-legged Frogs made extensive use of streams and riparian areas in their movements in late spring and early fall (Chan-McLeod 2003). Little is known about dispersal distances or the movements of juveniles (Ovaska and Sopuck 2004).
Habitats:
(Type / Subtype / Dependence) 		Forest / Deciduous/Broadleaf Forest / Facultative - occasional use
Grassland/Shrub / Meadow / Facultative - frequent use
Lakes / Lake / Obligate
Lakes / Pond/Open Water / Obligate
Riparian / Gravel Bar / Facultative - frequent use
Riparian / Riparian Forest / Facultative - frequent use
Riparian / Riparian Herbaceous / Facultative - frequent use
Riparian / Riparian Shrub / Facultative - frequent use
Stream/River / Stream/River / Facultative - frequent use
Wetland / Bog / Obligate
Wetland / Fen / Obligate
Wetland / Marsh / Obligate
Wetland / Swamp / Obligate
Global Habitat Comments: Habitat includes the vicinity of permanent waters of stream pools, marshes, ponds, and other quiet bodies of water. This frog regularly occurs in damp woods and meadows some distance from water, especially during wet weather. Individuals (especially juveniles) seasonally can be found in and near ephemeral pools. Estivation sites include small mammal burrows and moist leaf litter in dense riparian vegetation up to at least 26 meters from water (Rathbun et al. 1993, cited by USFWS 1994). Desiccation cracks in dry pond bottoms may be used as refuges (Alvarez, 2004, Herpetol. Rev. 35:162-163). Breeding sites most often are in permanent water; eggs are attached to stiff submerged stems at the surface of the water.
Provincial Habitat Comments: Red-legged Frogs have been observed in a variety of aquatic and terrestrial habitats. They breed in shallow, littoral zones of lakes, temporary and permanent pools and wetlands, and bogs and fens regardles of size but in close proximity to forest (i.e., toads may be found in all lacustrine and palustrine habitats); tadpoles associate with benthic habitats. Survival was higher in exclosures in temporary versus permanent wetlands in Washington (Adams 2000). Lotic habitats with little to no flow may be utilized by Red-legged Frogs, and riparian areas are important for newly metamorphosed froglets. Outside of the breeding season, Red-legged Frogs primarlily utilize all forest and woodland types, but individuals are occasionally found in more open and rural areas such as shrubland/chaparral, cropland/hedgerow, old fields, and suburban/orchard. Little is know about the habitat requirements of Red-legged Frogs during hibernation, but one study found frogs overwintering in terrestrial or aquatic habitats in the Lower Mainland (Licht 1969), and one radio-tracked frog on Vancouver Island was found overwintering in a stream bank (Chan-McLeod, pers. comm.). In California, Red-legged Frogs estivate in burrows and moist leaf litter (USFWS 1994). Red-legged Frogs are most common at elevations below 500 m, with low slopes, and containing moist, mature/old forest in some areas.
Food Habits: Herbivore:Immature
Invertivore: Adult
Global Food Habits Comments: Diet includes beetles, caterpillars, isopods, and various other small invertebrates (Nussbaum et al. 1983). In California, diet mainly invertebrates of shoreline or water surface; large adults also may eat small vertebartes. Larvae eat algae, organic debris, plant tissue, and other minute organisms.
Provincial Food Habits Comments: Adult and juvenile Red-legged Frogs are carnivorous, feeding mainly on invertebrates in terrestrial and riparian environments, such as spiders, beetles, leaf hoppers, damsel bugs, minute moss beetles, adult flies, and fly larvae (Licht 1986). Tadpoles are herbivorous, feeding mainly on filamentous green algae, and potentially suspended plant material or benthic detritus.
Global Phenology: Circadian: Adult, Immature
Hibernates/aestivates: Adult, Immature
Nocturnal: Adult, Immature
Global Phenology Comments: Inactive in cold temperatures and hot, dry weather. May be active all year in coastal areas, inactive late summer to early winter elsewhere (Zeiner et al. 1988). In California, adults and subadults apparently mainly nocturnal; juveniles active day or night (Hayes and Tennant 1985).
Provincial Phenology:
(1st half of month/
2nd half of month)
Provincial Phenology Comments: The active season and breeding period varies according to elevation, latitude and climate. In south-central British Columbia, Red-legged Frogs breed as soon as ice break-up, when water temperatures are 6-7 degrees Celcius (Licht 1974; Brown 1975b). Red-legged Frogs breed between February and April, depending on location (e.g., elevation). In general, frogs are active from early spring until late fall; adults emerge and breed in early spring, eggs and tadpoles are present in late spring and summer, and metamorphosis occurs in late summer. Red-legged frogs are inactive in the coldest periods of winter. On northern Vancouver Island, adult radio-tracked Red-legged Frogs moved mainly at night (Chan-McLeod 2001).
Colonial Breeder: N
Length(cm)/width(cm)/Weight(g): 14/ /
Elevation (m) (min / max): Global: 
Provincial:  0 / 1040
   
 
Distribution
Endemic: N
Global Range Comment: Range extends from southwestern British Columbia, including Vancouver Island in Canada, south along the coast of the United States (primarily west of Cascade-Sierran crest), to northwestern California (Shaffer et al. 2004). The species has been introduced and is well established and widely distributed on Graham Island, Queen Charlotte Islands (Haida Gwaii), British Columbia; it is unclear whether the species is native there or introduced many years ago (Ovaska et al. 2002). Rana aurora also is introduced and established on Chichagof Island, Alaska; the source of the frogs was Oregon (Hodge 2004).
 
Authors / Contributors
Global Information Author: Hammerson, G.
Last Updated: May 25, 2008
Provincial Information Author: Wind, E.
Last Updated: Dec 03, 2005
   
References and Related Literature
2001. Red-legged Frog. B.C. Minist. Environ., Lands and Parks, Wildl. Branch. 2pp.
Adams, M.J. 2000. Pond permanence and the effects of exotic vertebrates on anurans. Ecological Applications 10:559-568.
Altig, R. and Dumas, P.C. 1972. Rana aurora. Catalogue of American Amphibians and Reptiles. 160:1-4.
Behler, J. L., and F. W. King. 1979. The Audubon Society field guide to North American reptiles and amphibians. Alfred A. Knopf, New York. 719 pp.
Biosystems Analysis, Inc. 1989. Endangered Species Alert Program Manual: Species Accounts and Procedures. Southern California Edison Environmental Affairs Division.
Briggs, J. L., Sr. 1987. Breeding biology of the Cascade frog, Rana cascadae, with comparisons to R. aurora and R. pretiosa. Copeia 1987:241-245.
British Columbia Ministry of Water, Land and Air Protection. 2004. Red-legged Frog in Accounts and measures for managing identified wildlife. British Columbia Ministry of Water, Land and Air Protection, Victoria, BC. 52pp.
Brown, H. A. 1975b. Reproduction and development of the red-legged frog, Rana aurora, in northwestern Washington. Northwest Science 49:241-252.
Brown, H.A. 1975. Reproduction and development of the red-legged frog, Rana aurora, in northwestern Washington. North-west Science 49(4):241-252.
Calef, G. W. 1973. Natural mortality of tadpoles in a population of Rana aurora. Ecology 54:741-758.
Chan-McLeod, A. 2001. Effects of variable-retention harvest methods on movement patterns of Red-Legged Frogs. Unpublished progress report prepared for Weyerhaeuser Company, Nanaimo, BC.
Chan-McLeod, A. C. A. 2003. Factors affecting the permeability of clearcuts to red-legged frogs. Journal of Wildlife Management 67:663-671.
Corkran, C. C., and C. Thoms. 1996. Amphibians of Oregon, Washington and British Columbia. Lone Pine Publishing, Edmonton, Alberta. 175 pp.
COSEWIC. 2002k. COSEWIC assessment and status report on the red-legged frog Rana aurora. Committee on the Status of Endangered Wildlife in Canada. Ottawa. v + 22 pp.
COSEWIC. 2004n. COSEWIC assessment and update status report on the Red-legged Frog Rana aurora in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vi + 46 pp.
Cowan, I. McT. 1941. Longevity of the red-legged frog. Copeia 1941:48.
Fellers, G. M., A. E. Launer, G. Rathbun, S. Bobzien, J. Alvarez, D. Sterner, R. B. Seymour, and M. Westphal. 2001. Overwintering tadpoles in the California red-legged frog (Rana aurora draytonii). Herpetological Review 32:156-157.
Green, D. M. 1985. Biochemical identification of red-legged frogs, Rana aurora draytoni, at Duckwater, Nevada. Southwestern Naturalist 30:614-616.
Green, D.M. 1986a. Systematics and evolution of western North American frogs allied to Rana aurora and Rana boylii: karyological evidence. Systematic Zoology 35:273-282.
Green, D.M. 1986b. Systematics and evolution of western North American frogs allied to Rana aurora and Rana boylii: electrophoretic evidence. Systematic Zoology 35:283-296.
Green, D.M., and R.W. Campbell. 1984. The Amphibians of British Columbia. Royal B.C. Mus. Handb. No. 45. 101pp.
Hayes, M. P., and M. M. Miyamoto. 1984. Biochemical, behavioral and body size differences between Rana aurora aurora and R. a. draytoni. Copeia 1984:1018-1022.
Hayes, M. P., and M. R. Jennings. 1988. Habitat correlates of distribution of the California red-legged frog (Rana aurora) and the foothill yellow-legged frog (Rana boylii): implications for management. Pages 144-158 in Szaro, R.C., et al., technical coordinators. Management of amphibians, reptiles, and small mammals in North America. USDA For. Serv., Gen. Tech. Rep. RM-166.
Hayes, M. P., and M. R. Tennant. 1985. Diet and feeding behavior of the California red-legged frog, Rana aurora draytoni (Ranidae). Southwestern Naturalist 30:601-605.
Hayes, M. P., C. A. Pearl, and C. J. Rombough. 2001. Rana aurora aurora. Movement. Herpetological Review 32:35-36.
Hayes, M. P., C.A. Pearl, and C.J. Rombough. 2001. Rana aurora aurora (northern red-legged frog). Movement. Herpetological Review 32:35-36.
Licht, L. E. 1969. Comparative breeding behavior of the red-legged frog, (Rana aurora aurora) and the western spotted frog (Rana pretiosa pretiosa) in southwestern British Columbia. Canadian Journal of Zoology 47:1287-1299.
Licht, L. E. 1974. Survival of embryos, tadpoles, and adults of the frogs Rana aurora aurora and Rana pretiosa sympatric in southwestern British Columbia. Canadian Journal of Zoology 52:613-627.
Licht, L. E. 1986. Food and feeding behavior of sympatric red-legged frogs, Rana aurora and spotted frogs, Rana pretiosa, in southwestern British Columbia. Canadian Field-Naturalist 100:22-31.
Licht, L.E. 1971. Breeding habits and embryonic thermal requirements of the frogs, Rana aurora aurora and Rana pretiosa pretiosa, in the Pacific Northwest. Ecology 52(1):116-124.
Nussbaum, R.A., E.D. Brodie, Jr., and R.M. Storm. 1983. Amphibians and Reptiles of the Pacific Northwest. University Press of Idaho, Moscow, Idaho. 332 pp.
Ovaska, K, S. Lennart, C Engelstoft, L. Matthias, E. Wind and J. MacGarvie. 2004. Best Management Practices for Amphibians and Reptiles in Urban and Rural Environments in British Columbia. Ministry of Water Land and Air Protection, Ecosystems Standards and Planning, Biodiversity Branch
Ovaska, K. and L. Sopuck. 2004. Update COSEWIC Status Report on the Red-legged Frog Rana aurora in Canada. Unpublished revised report prepared for COSEWIC. 63 pp.
Shean, J. T. S. 2002. Post-breeding movements and habitat use by the Northern Red-legged Frog, Rana aurora aurora, at Dempsey Creek, Thurston County, Washington. M.Sc. Thesis, Evergreen State College, Olympia, Washington, U.S.A.
Stebbins, R. C. 1985a. A field guide to western reptiles and amphibians. Second edition. Houghton Mifflin Company, Boston, Massachusetts. xiv + 336 pp.
U.S. Fish and Wildlife Service (USFWS). 1994. Proposed endanagered status for the California Red-legged frog. Federal Register 2. 59(22):4888-4895.
U.S. Fish and Wildlife Service (USFWS). 1994. Proposed endangered status for the California red-legged frog. Federal Register 59(22):4888-4895. 2 February 1994.
Waye, H. 1999. COSEWIC status report on the Red-legged Frog (Rana aurora) in Canada. Unpublished report prepared for the Committee on the Status of Endangered Wildlife in Canada. 27 pp.
Zeiner, D.C., W.F. Laudenslayer, Jr., and K.E. Mayer, editors. 1988. Califonia's wildlife. Vol. I. Amphibians and reptiles. California Dept. Fish and Game, Sacramento. ix + 272 pp.
 

Please visit the website Conservation Status Ranks for definitions of the data fields used in this summary report.

Suggested Citation:

B.C. Conservation Data Centre. 2008. Species Summary: Rana aurora. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Aug 29, 2025).