Overview

Comprehensive Description

Description

Adult R. Aurora range from 4.4 to 8.4 cm in length, with females significantly larger than males (Stebbins 1985; Hayes and Miyamoto 1984). The abdomen and underside of hind legs is characterized by a red or pinkish color, often set on a yellowish ground color (Stebbins 1985). Back is a brown, gray, olive, or reddish color, often with may small black flecks and irregular dark splotches, in some individuals forming a network of black lines (Stebbins 1985). Dorsolateral folds are prominent. Tadpoles range in length from 14 to 80 mm, and are a dark brown or olive, marked with darker spots (Storer 1925).

R. aurora differs from its close relative, the California red legged frog, R. draytonii in several ways. Adult R. draytonii are 35 to 40 millimeters longer than adult R. aurora (Hayes and Miyamoto 1984). The dorsal spots of R. draytonii are more numerous, and usually have light centers (Stebbins 1985). R. draytonii also has rougher skin, shorter limbs and smaller eyes than R. aurora (Stebbins 1985). R. draytonii has paired vocal sacs and typically calls from the air , while R. aurora lacks vocal sacks ( Hayes and Krempels 1986; Licht 1969). Egg masses in R. draytonii are deposited such that the mass floats at the surface (Hayes and Miyamoto 1984), whereas R. aurora submerge the mass in deeper water (Licht 1969; Storm 1960). R. draytonii breed from November to April (Storer 1925), while R. aurora breeds from January to March (Nussbaum et al 1983).

See other subspecies accounts at www.californiaherps.com: R. a. aurora and R. a. draytonii.

  • Hayes, M. P. and Krempels, D.M. (1986). ''Vocal sac variation among frogs of the genus Rana from western North America.'' Copeia, 1986(4), 927-936.
  • Hayes, M. P. and Miyamoto, M. M. (1984). ''Biochemical, behavioral and body size difference between Rana aurora aurora and R. a. draytonii.'' Copeia, 1984(4), 1018-1022.
  • Hayes, M. P. and Tennant, M. R. (1985). ''Diet and feeding behavior of the California Red-legged Frog Rana aurora draytonii (Ranidae).'' The Southwestern Naturalist, 30(4), 601-605.
  • Jennings, M. (1988). ''Natural history and decline of native ranids in California.'' Proceedings of the Conference on California Herpetology. H.F. DeLise, P.R. Brown, B. Kaufman, and B.M. McGurty, eds., Southwestern Herpetologists Society Special Publication, 1-143.
  • Jennings, M.R. and Hayes, M.P. (1985). ''Pre-1900 overharvest of California Red-legged Frogs (Rana aurora draytonii):The inducement for bullfrog (Rana catesbeiana) introduction.'' Herpetological Review, 31(1), 94-103.
  • Jennings, M.R. and Hayes, M.P. (1990). ''Final report on the status of the California Red-Legged Frog in the Pescadero Marsh Natural Preserve. Prepared for the California Department of Parks and Recreation under contract no. 4-823-9081 with the California Academy of Sciences.''
  • Jennings, M.R., Hayes, M.P. and Holland, D.C. (1992). A petition to the U.S. Fish and Wildlife Service to place the California Red-legged Frog (Rana aurora draytonii) and the Western Pond Turtle (Clemmys marmorata) on the list of endangered and threatened wildlife and plants.
  • 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(6), 1287-1299.
  • Nussbaum, R. A., Brodie, E. D., Jr., and Storm, R. M. (1983). Amphibians and Reptiles of the Pacific Northwest. University of Idaho Press, Moscow, Idaho.
  • Rathbun, G.B., and Murphy, T.G. (1996). ''Evaluation of a radio-belt for ranid frogs.'' Herpetological Review, 27(4), 197-199.
  • Scott, N. and Rathbun, G. (1998). ''Essays provided to Ina Pisani in response to a working draft of California red-legged frog recovery plan.''
  • Stebbins, R. C. (1985). A Field Guide to Western Reptiles and Amphibians. Houghton Mifflin, Boston.
  • Storer, T. I. (1925). "A synopsis of the amphibia of California." University of California Publications in Zoology, 27, 1-342.
  • Storm, R.M. (1960). ''Notes on the breeding biology of the Red-legged Frog (Rana aurora aurora).'' Herpetologica, 16, 251-259.
  • U.S. Fish and Wildlife Service (2002). Recovery Plan for the California Red-legged Frog (Rana aurora draytonii). U.S. Fish and Wildlife Service, Portland, Oregon.
  • Wright, A. H. and Wright, A. A. (1949). Handbook of Frogs and Toads of the United States and Canada. Comstock Publishing Company, Inc., Ithaca, New York.
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Distribution

National Distribution

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

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Rana aurora occcurs in the state of California in North America. Two subspecies of R. aurora occupy different ranges within the state. The first, Rana aurora aurora, or the Northern Red-legged frog, occupies the extreme northwestern corner of Calfornia, north to southern British Columbia, west of the Cascade crest. The second, Rana aurora draytonii, or the Calfornia Red-legged frog, occupies central and southern portions of the state, west of the Sierran divides and into the mountains of southern California up to an altitude of 4000 feet.

(Grinnell, 1917; Defenders of Wildlife; Davidson, 1996)

Biogeographic Regions: nearctic (Native )

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Range Description

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).
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Global Range: (200,000-2,500,000 square km (about 80,000-1,000,000 square miles)) 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).

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Distribution and Habitat

R. aurora ranges from Vancouver Island, British Columbia, Canada, south along the Pacific coast, west of the Cascade Ranges to Northern California. R. aurora live in areas subject to temporal and spatial changes, and therefore make use of a variety of habits, consisting of both aquatic, upland and riparian (Draft Recovery Plan). Adults breed in ponds or deep pools in slow-moving creeks. Where ponds are seasonal in nature, thickets and logjams along riparian corridors provide important non-breeding habitat. Populations are most likely to persist in areas with multiple breeding sites surrounded by suitable non-breeding habitat (N. Scott and G. Rathbun in litt. 1998).

  • Hayes, M. P. and Krempels, D.M. (1986). ''Vocal sac variation among frogs of the genus Rana from western North America.'' Copeia, 1986(4), 927-936.
  • Hayes, M. P. and Miyamoto, M. M. (1984). ''Biochemical, behavioral and body size difference between Rana aurora aurora and R. a. draytonii.'' Copeia, 1984(4), 1018-1022.
  • Hayes, M. P. and Tennant, M. R. (1985). ''Diet and feeding behavior of the California Red-legged Frog Rana aurora draytonii (Ranidae).'' The Southwestern Naturalist, 30(4), 601-605.
  • Jennings, M. (1988). ''Natural history and decline of native ranids in California.'' Proceedings of the Conference on California Herpetology. H.F. DeLise, P.R. Brown, B. Kaufman, and B.M. McGurty, eds., Southwestern Herpetologists Society Special Publication, 1-143.
  • Jennings, M.R. and Hayes, M.P. (1985). ''Pre-1900 overharvest of California Red-legged Frogs (Rana aurora draytonii):The inducement for bullfrog (Rana catesbeiana) introduction.'' Herpetological Review, 31(1), 94-103.
  • Jennings, M.R. and Hayes, M.P. (1990). ''Final report on the status of the California Red-Legged Frog in the Pescadero Marsh Natural Preserve. Prepared for the California Department of Parks and Recreation under contract no. 4-823-9081 with the California Academy of Sciences.''
  • Jennings, M.R., Hayes, M.P. and Holland, D.C. (1992). A petition to the U.S. Fish and Wildlife Service to place the California Red-legged Frog (Rana aurora draytonii) and the Western Pond Turtle (Clemmys marmorata) on the list of endangered and threatened wildlife and plants.
  • 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(6), 1287-1299.
  • Nussbaum, R. A., Brodie, E. D., Jr., and Storm, R. M. (1983). Amphibians and Reptiles of the Pacific Northwest. University of Idaho Press, Moscow, Idaho.
  • Rathbun, G.B., and Murphy, T.G. (1996). ''Evaluation of a radio-belt for ranid frogs.'' Herpetological Review, 27(4), 197-199.
  • Scott, N. and Rathbun, G. (1998). ''Essays provided to Ina Pisani in response to a working draft of California red-legged frog recovery plan.''
  • Stebbins, R. C. (1985). A Field Guide to Western Reptiles and Amphibians. Houghton Mifflin, Boston.
  • Storer, T. I. (1925). "A synopsis of the amphibia of California." University of California Publications in Zoology, 27, 1-342.
  • Storm, R.M. (1960). ''Notes on the breeding biology of the Red-legged Frog (Rana aurora aurora).'' Herpetologica, 16, 251-259.
  • U.S. Fish and Wildlife Service (2002). Recovery Plan for the California Red-legged Frog (Rana aurora draytonii). U.S. Fish and Wildlife Service, Portland, Oregon.
  • Wright, A. H. and Wright, A. A. (1949). Handbook of Frogs and Toads of the United States and Canada. Comstock Publishing Company, Inc., Ithaca, New York.
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Physical Description

Morphology

Rana aurora reaches from 2 to 5.25 inches in length. It is reddish brown to gray and contains many poorly defined dark specks and blotches, which are absent on the back and top of its head. A light stripe on its jaw borders its dark mask. Folds are present on its back and sides, and the underside is yellow with red on the lower abdomen and hind legs. Its toes are not fully webbed. Females grow larger than males. Males, however, have enlarged forearms and swollen thumbs. Rana aurora aurora has very smooth and thin skin and an unspotted dorsal surface. Rana aurora draytonii has thick, rough skin, light centered spots on its dorsal surface, and a larger build. Northern red-legged frogs have no vocal sacs while Southern red-legged frogs have paired vocal sacs.

(Green,1996; Hayes, 1986; Thomas,1993; USFW, 1996; Defenders of Wildlife)

Other Physical Features: ectothermic ; bilateral symmetry

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Size

Length: 14 cm

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Diagnostic Description

Differs from R. PRETIOSA in having a mottled groin, eyes that are not turned upward, and the light jaw stripe ending before the shoulder rather than usually reaching the shoulder. Differs from R. CASCADAE in having less well-defined black spots on the dorsum, usually red rather than yellow on the lower abdomen and underside of the limbs, a more mottled groin, and generally smoother skin. Differs from R. BOYLII in having usually red rather than yellow on the underside of the limbs, a dark mask, prominent rather than indistinct dorsolateral folds, and smooth rather than granular eyedrums. (Stebbins 1985).

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Type Information

Syntype for Rana aurora
Catalog Number: USNM 11711
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Preparation: Ethanol
Year Collected: 1841
Locality: Puget Sound, Locality In Multiple Counties, Washington, United States, North America
  • Syntype: Baird, S. F. & Girard, C. 1852. Proc. Acad. Nat. Sci. Philadelphia. 6: 174.
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Paralectotype for Rana aurora
Catalog Number: USNM 498962
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Preparation: Ethanol
Year Collected: 1841
Locality: Puget Sound, Locality In Multiple Counties, Washington, United States, North America
  • Paralectotype: Green, D. M., et al. 1997. Copeia. 1997 (1): 5.; Baird, S. F. & Girard, C. 1853. Proc. Acad. Nat. Sci. Philadelphia. 6: 378.
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Paralectotype for Rana aurora
Catalog Number: USNM 498961
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Preparation: Ethanol
Year Collected: 1841
Locality: Puget Sound, Locality In Multiple Counties, Washington, United States, North America
  • Paralectotype: Green, D. M., et al. 1997. Copeia. 1997 (1): 5.; Baird, S. F. & Girard, C. 1853. Proc. Acad. Nat. Sci. Philadelphia. 6: 378.
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Ecology

Habitat

California Montane Chaparral and Woodlands Habitat

This taxon can be found in the California montane chaparral and woodlands, a near coastal ecoregion in Central and Southern California, USA. This ecoregion is disjunctive, with a major element in Southern California and another along the Monterey County coast. The ecoregion encompasses most of the Transverse Range that includes the San Bernardino Mountains; San Gabriel Mountains; portions of the Santa Ynez and San Rafael Mountains; Topatopa Mountains; San Jacinto Mountains; the Tehachapi, Greenhorn, Piute, and Kiavah Mountains that extend roughly northeast-southwest from the southern Sierra Nevada; and the Santa Lucia Range that parallels the coast southward from Monterey Bay to Morro Bay.

The California montane chaparral and woodland ecoregion consists of a complex mosaic of coastal sage scrub, lower chaparral dominated by chamise, upper chaparral dominated by manzanita, desert chaparral, Piñon-juniper woodland, oak woodlands, closed-cone pine forests, yellow pine forests, sugar pine-white fir forests, lodgepole pine forests, and alpine habitats. The prevalence of drought-adapted scrub species in the flora of this ecoregion helps distinguish it from similar communities in the Sierras and other portions of northern California. Many of the shared Sierra Nevadan species typically are adapted to drier habitats in that ecoregion, Jeffrey Pine (Pinus jeffreyi) being a good example.

Oak species are an important component of many chaparral and forest communities throughout the ecoregion. Canyon Live Oak, Interior Live Oak, Tanbark Oak (not a true Quercus species), Engelmann Oak, Golden-cup Oak, and Scrub Oak are some examples. Mixed-conifer forests are found between 1371 to 2896 meters elevation with various combinations and dominance of incense cedar, sugar pine, and white fir, Jeffrey Pine, Ponderosa Pine, and mountain juniper. Subalpine forests consist of groves of Limber Pine (Pinus flexilis), Lodgepole Pine, and Jeffrey Pine. Very old individual trees are commonly observed in these relict subalpine forests. Within this zone are subalpine wet meadows, talus slope herbaceous communities, krumholz woodlands, and a few small aspen groves.

In addition to these general vegetation patterns, this ecoregion is noted for a variety of ecologic islands, communities with specialized conditions that are widely scattered and isolated and typically harbor endemic and relict species. Examples include two localities of Knobcone Pine (Pinus attenuata) on serpentine soils, scattered vernal pools with a number of endemic and relict species, and isolated populations of one of North America’s most diverse cypress floras, including the rare Gowen Cypress (Cupressus goveniana goveniana) restricted to two sites on acidic soils in the northern Santa Lucia Range, Monterey Cypress (Cupressus macrocarpa) found only at two coastal localities near Monterey Bay, and Sargent Cypress (Callitropsis sargentii LR/LC) restricted to serpentine outcrops. Monterey Pine (Pinus radiata) is also restricted to three coastal sites near Monterey Bay.

The ecoregion is also home to a few endemic or near-endemic mammalian vertebrates, such as the White-eared Pocket Mouse (Perognathus alticolus EN), a mammal known only to two disjunct mountain ranges in southern California: San Bernardino Mountains in San Bernardino County (ssp. alticolus), and the Tehachapi Mountains, in Kern, Ventura, and Los Angeles counties. The near-endemic fossorial Agile Kangaroo Rat (Dipodomys agilis) is found in the southern disjunctive unit of the ecoregion, and is known only to the Los Angeles Basin and foothills of San Gabriel and San Bernardino mountains in Ventura, Los Angeles, and Riverside counties north to Santa Barbara County and through the southern Sierra Nevada, including Mount Pinos, Tehachapi and San Gabriel mountains, and northern San Fernando Valley. Non-endemic mammals found in the ecoregion include Botta's Pocket Gopher (Thomomys bottae) and Trowbridge's Shrew (Sorex trowbridgii). Some larger vertebrate predators can be found in the ecoregion, including Puma (Puma concolor), Bobcat (Lynx rufus), Coyote (Canis latrans), and Ringtails (Bassariscus astutus).

The ecoregion boasts five endemic and near-endemic amphibians, largely Plethodontid salamanders. Some specific salamander taxa found here are the endemic Tehachapi Slender Salamander (Batrachoseps stebbinsi VU), known from isolated sites in the Caliente Creek drainage, Piute Mountains, and Kern County, California along with scattered populations in the Tehachapi Mountains to Fort Tejon, Kern County; the near-endemic Blackbelly Slender Salamander (Batrachoseps nigriventris); the Monterey Ensatina (Ensatina eschscholtzii); the Channel Islands Slender Salamander (Batrachoseps pacificus), endemic to a narrow range restricted solely on Anacapa, Santa Cruz, Santa Rosa, and San Miguel islands; and the Arboreal Salamander (Aneides lugubris), found only in California and Baja California. A newt found here is the Coast Range Newt (Taricha torosa). Anuran taxa in the ecoregion include the Foothill Yellow-legged Frog (Rana boylii NT); the Southern Mountain Yellow-legged Frog (Rana muscosa EN), a California endemic occurring in several disjunctive populations; and the Northern Red-legged Frog (Rana aurora).

The California montane chaparral and woodlands ecoregions contains a number of reptiles such as the Coast Horned Lizard (Phrynosoma coronatum), who ranges from Northern California to Baja California. Also found here is the Sagebrush Lizard (Sceloporus graciosus); the Western Fence Lizard (Sceloporus occidentalis); the Southern Alligator Lizard (Elgaria multicarinata); and the Side-blotched Lizard (Uta stansburiana). The Two-striped Garter Snake (Thamnophis hammondii) is a restricted range reptile found near-coastally from Monterey County, California southward to Baja California.

The California Condor once inhabited much of the ecoregion, with the western Transverse Range acting today as a refuge for some of the last wild populations, after considerable conservation efforts, especially in the Los Padres National Forest. The Heermann's Gull (Larus heermanni NT) is found in coastal areas of the ecoregion.

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Adult frogs must have emergent riparian vegetation near deep, still or slow-moving ponds or intermittent streams. These well-vegetated areas along the river are needed for escaping from predators, for shade to maintain cool water temperatures, and as shelter especially during the winter. Rana aurora aurora has the lowest upper and lower embryonic temperatures of any North American ranid frog, ranging from 4 to 21 degrees Celsius. Rana aurora draytonii cannot be exposed to water temperatures much higher than 29 degrees Celsius. They are found more often in intermittent than permanent waters because of predators that inhabit permanent waters. Red-legged frogs may move out of riparian zones into nearby upland forest during non-breeding seasons. R. a. draytonii may move seasonally within their aquatic habitats between places where they breed and foraging habitats.

(Cole, 1997; Defenders of Wildlife; Davidson, 1996)

Aquatic Biomes: lakes and ponds; rivers and streams

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Habitat and Ecology

Habitat and Ecology
Habitat includes the vicinity of quiet permanent waters of streams, marshes, or (less often) ponds and other quiet bodies of water. The frogs are sometimes found in damp woods and meadows some distance from water, especially during wet weather. This species occurs in sites with dense vegetation (e.g., willows) close to water and some shading. Red-legged frogs may occupy ephemeral pools if the water remains until late spring or early summer (Biosystems Analysis 1989). Estivation sites include small mammal burrows and moist leaf litter in dense riparian vegetation up to 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.

Systems
  • Terrestrial
  • Freshwater
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Central Pacific Coastal Forests Habitat

This taxon is found in the Central Pacific Coastal Forests ecoregion, as one of its North American ecoregions of occurrence. These mixed conifer rainforests stretch from stretch from southern Oregon in the USA to the northern tip of Vancouver Island, Canada. These forests are among the most productive in the world, characterized by large trees, substantial woody debris, luxuriant growths of mosses and lichens, and abundant ferns and herbs on the forest floor. The major forest complex consists of Douglas-fir (Pseudotsuga menziesii) and Western hemlock (Tsuga heterophylla), encompassing seral forests dominated by Douglas-fir and massive old-growth forests of Douglas-fir, Western hemlock, Western red cedar (Thuja plicata), and other species. These forests occur from sea level up to elevations of 700-1000 meters in the Coast Range and Olympic Mountains. Such forests occupy a gamut of environments with variable composition and structure and includes such other species as Grand fir (Abies grandis), Sitka spruce (Picea sitchensis), and Western white pine (Pinus monticola).

Characteristic mammalian fauna include Elk (Cervus elaphus), Black-tailed Deer (Odocoileus hemionus), Coyote (Canis latrans), Black Bear (Ursus americanus), Mink (Mustela vison), and Raccoon (Procyon lotor).

The following anuran species occur in the Central Pacific coastal forests: Coastal tailed frog (Ascaphus truei); Oregon spotted frog (Rana pretiosa VU); Northern red-legged frog (Rana pretiosa); Pacific chorus frog (Pseudacris regilla); Cascade frog (Rana cascadae NT), generally restricted to the Cascade Range from northern Washington to the California border; Foothill yellow-legged frog (Rana boylii) and the Western toad (Anaxyrus boreas NT).  A newt found in the ecoregion is the Rough skinned newt (Taricha granulosa).

Salamanders within the ecoregion are: Del Norte salamander (Plethodon elongatus NT);  Van Dyke's salamander (Plethodon vandykei); Western redback salamander (Plethodon vehiculum); Northwestern salamander (Ambystoma gracile);  Olympic torrent salamander (Rhyacotriton olympicus VU), whose preferred habitat is along richly leafed stream edges; Long-toed salamander (Ambystoma macrodactylum), whose adults are always subterranean except during the breeding season; Dunn's salamander (Plethodon dunni), usually found in seeps and stream splash zones; Clouded salamander (Aneides ferreus NT), an aggressive insectivore; Monterey ensatina (Ensatina eschscholtzii), usually found in thermally insulated micro-habitats such as under logs and rocks; Pacific giant salamander (Dicamptodon tenebrosus), found in damp, dense forests near streams; and Cope's giant salamander (Dicamptodon copei), usually found in rapidly flowing waters on the Olympic Peninsula and Cascade Range.

There are a small number of reptilian taxa that are observed within this forested ecoregion, including: Pacific pond turtle (Emys marmorata); Common garter snake (Thamnophis sirtalis), an adaptable snake most often found near water; Northern alligator lizard (Elgaria coerulea); and the Western fence lizard.

Numerous avian species are found in the ecoregion, both resident and migratory. Example taxa occurring here are the Belted kingfisher (Megaceryle alcyon); Wild turkey (Meleagris gallopavo); and the White-headed woodpecker (Picoides albolarvatus) and the Trumpeter swan (Cygnus buccinator), the largest of the North American waterfowl.

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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.

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Migration

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

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).

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Trophic Strategy

Red-legged frogs have a highly variable diet, eating any prey they can subdue that is not distasteful. Adults feed on invertebrates, small mammals and other amphibians like the small tree frog. Larvae are thought to feed on algae.

(Davidson, 1996; Defenders of Wildlife)

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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.

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Population Biology

Number of Occurrences

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 - 300

Comments: This species is represented by a large number of occurrences.

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Global Abundance

10,000 - 1,000,000 individuals

Comments: Total adult population size is unknown but presumably exceeds 10,000. This species is relatively widespread and common over most of its range (McAllister and Leonard, in Jones et al. 2005; Pearl in Lannoo 2005).

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Life History and Behavior

Cyclicity

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).

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Life Cycle

Development - Life Cycle: metamorphosis

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Life Expectancy

Average lifespan

Status: captivity:
15 years.

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Lifespan, longevity, and ageing

Maximum longevity: 15 years (wild) Observations: Animals living in the north, also called Northern red-legged frogs, appear to develop slower, probably due to the colder water temperatures, and live longer. In California, maximum lifespan is probably around 10 years. Northern frogs also lay fewer eggs.
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Reproduction

Reproduction in Northern Red-legged frogs occurs from late November to early April to ensure cool water, six or seven degrees Celsius. These conditions ensure embroyonic survival and sufficient water for larval growth and metamorphosis. Red-legged frogs breed via external fertilization. The male grasps the female in a process call amplexus, and while the female lays her eggs, he fertilizes them with a fluid containing sperm. The female lays egg masses (ranging from 2000 to 5000 eggs in R. a. draytonii and 500-1100 in R. a. aurora) in permanent bodies of water that contain extensive vegetation, consisting of cattails and tules or bulrushes growing in the water with a vertical orientation. R. a. draytonii eggs are attached at or near the surface of the water while R. a. aurora eggs are attached at a minimum depth of eighteen inches and at least two to three feet from the water's edge. The eggs are dark brown and range from 2.0 to 2.8 millimeters in diameter. The eggs hatch anywhere from six to fourteen days between July and September into brown tadpoles that can reach around three inches long within four to seven months. They then grow legs, lose their tales, and change into a juvenile form of the adult frog with dark masks on their faces and bright orange folds on their backs. As they grow into adults, the froglets move from shallow water to knee-deep water to hide from larger predators. Males can probably reproduce after three years of age while females reproduce after four. Life spans of the California Red-legged frog are about eight years for males and ten for females, while Northern red-legged frogs live twelve to fifteen years.

(Hickman and Roberts, 1995; Jennings, 1985; Davidson, 1996; USFW 1996; Defenders of Wildlife)

Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate)

Average number of offspring: 2000.

Average age at sexual or reproductive maturity (male)

Sex: male:
1095 days.

Average age at sexual or reproductive maturity (female)

Sex: female:
1460 days.

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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.

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Conservation

Conservation Status

Rana aurora draytonii has been declared a threatened species by the Fish and Wildlife Services following a year-long Congressional moratorium on listings which began April of 1995 and was lifted the next April by President Clinton. Rana aurora draytonii was harvested at the turn of the century for its prized frog legs. As a result of this overharvesting, populations declined drastically. Bullfrogs that eat the eggs of R. a. draytonii were introduced as a substitute for the red-legged frogs, along with non-native fish, and replaced them in habitat. Exotic plant species have also taken over the riparian habitat of R. a. draytonii. Dam construction also poses a threat to the frogs, it destroys and fragments its habitat and reservoirs favor aquatic predators. Road-building has also put silt into pools that the frogs dwell in, and flood projects along with livestock grazing along streams destroy emergent vegetation. Pollution from garbage and sewage contaminate the clean waters that provide a habitat for the frogs. R. a. draytonii has disappeared from 75 percent of its historic range. A few things are being done to help this subspecies recover. Dense stands of riparian vegetation in slow or still waters are being maintained along with sufficient water depth for these frogs. Silt removal is being proposed during fall months so as not to disturb the breeding season. Exotic plant species are being removed and red-legged frog tadpoles are being introduced. Fences and buffer zones around frog habitats are also being proposed to cattle ranchers. Results of studies on clear-cutting have shown that R.aurora was found more frequently in riparian environments than upslope areas.

(Cole, 1997; Davidson, 1996; USFW 1996, Defenders of Wildlife)

US Federal List: threatened

IUCN Red List of Threatened Species: least concern

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IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2008

Assessor/s
Geoffrey Hammerson

Reviewer/s
Global Amphibian Assessment Coordinating Team (Simon Stuart, Janice Chanson, Neil Cox and Bruce Young)

Contributor/s

Justification
Listed as Least Concern in view of the wide distribution, numerous subpopulations, ability to use altered habitats, presumed large population, and because it is unlikely to be declining fast enough to qualify for listing in a more threatened category.

History
  • 2004
    Near Threatened
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National NatureServe Conservation Status

Canada

Rounded National Status Rank: N3 - Vulnerable

United States

Rounded National Status Rank: N4 - Apparently Secure

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NatureServe Conservation Status

Rounded Global Status Rank: G4 - Apparently Secure

Reasons: Large range in western North America; substantial declines in some areas; still widespread, common, and apparently secure in many areas; warrants rangewide monitoring.

Intrinsic Vulnerability: Moderately vulnerable

Environmental Specificity: Moderate. Generalist or community with some key requirements scarce.

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Population

Population
This species is represented by a large number of occurrences. Total adult population size is unknown but presumably exceeds 10,000. This species is relatively widespread and common over most of its range (McAllister and Leonard, in Jones et al. 2005; Pearl in Lannoo 2005).

Over the long term, extent of occurrence, area of occurrence, number/condition of subpoppulations, and population size have declined, but the amount of decline is uncertain. Currently, area of occupancy, number of subpopulations, and population size probably are declining, though the magnitude of the decline is uncertain.

Population Trend
Stable
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Global Short Term Trend: Relatively stable to decline of 30%

Comments: Currently, area of occupancy, number of subpopulations, and population size probably are declining, though the magnitude of the decline is uncertain.

Global Long Term Trend: Decline of 30-50%

Comments: Over the long term, extent of occurrence, area of occurrence, number/condition of subpoppulations, and population size have declined, but the amount of decline is uncertain.

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Life History, Abundance, Activity, and Special Behaviors

R. aurora breed during a 1-2 week period between January and March, depending on locality (Stebbins 1985; Nussbaum et al. 1983). Egg masses consist of between 300 and 5,000 eggs (Recovery Plan for the California Red-legged Frog 2002; Storer 1925; Fellers unpubl.). Egg masses are nearly always attached to emergent vegetation, submerged beneath the surface in the deepest water available (Hayes and Miyamoto 1984; Licht 1969; Storm 1960). Eggs hatch after 6 to 14 days depending on water temperature ( Jennings 1988). Larvae typically metamorphose in 3.5 to 7 months ( Storer 1925; Wright and Wright 1949), but some overwinter and transform after more than 12 months in the larval stage (Fellers et al. in press). Males may attain sexual maturity at 2 years, females at 3 (Jennings and Hayes 1985), and adult frogs may live 8 to 10 years. (Jennings et al in lit 1992). Larvae are thought to be algal grazers ( Jennings et al in lit 1992), and the adult diet consists mostly of invertebrates. Pacific Tree Fogs (Hyla regilla) and California mice (Peromyscus californicus are occasionally consumed by adult frogs ( Hayes and Tennant 1985). Juvenile frogs may be active both nocturnally and diurnally, whereas adult frogs are primarily active nocturnally ( Hayes and Tennant 1985). The primary predators on R. aurora include garter snakes (Thamnophis spp.), raccoons (Procyon lotor), and great blue herons (Ardea herodias). Less frequently, red-legged frogs are eaten by American bitterns (Botaurus lentiginosus), black-crowned night herons(Nycticorax nycticorax), and rarely by red-shouldered hawks (Buteo lineatus)(Jennings and Hayes 1990; Rathbun and Murphy 1996). Other introduced species such as the bullfrog (Rana catesbeiana) and non-native fish also prey on the frog.

  • Hayes, M. P. and Krempels, D.M. (1986). ''Vocal sac variation among frogs of the genus Rana from western North America.'' Copeia, 1986(4), 927-936.
  • Hayes, M. P. and Miyamoto, M. M. (1984). ''Biochemical, behavioral and body size difference between Rana aurora aurora and R. a. draytonii.'' Copeia, 1984(4), 1018-1022.
  • Hayes, M. P. and Tennant, M. R. (1985). ''Diet and feeding behavior of the California Red-legged Frog Rana aurora draytonii (Ranidae).'' The Southwestern Naturalist, 30(4), 601-605.
  • Jennings, M. (1988). ''Natural history and decline of native ranids in California.'' Proceedings of the Conference on California Herpetology. H.F. DeLise, P.R. Brown, B. Kaufman, and B.M. McGurty, eds., Southwestern Herpetologists Society Special Publication, 1-143.
  • Jennings, M.R. and Hayes, M.P. (1985). ''Pre-1900 overharvest of California Red-legged Frogs (Rana aurora draytonii):The inducement for bullfrog (Rana catesbeiana) introduction.'' Herpetological Review, 31(1), 94-103.
  • Jennings, M.R. and Hayes, M.P. (1990). ''Final report on the status of the California Red-Legged Frog in the Pescadero Marsh Natural Preserve. Prepared for the California Department of Parks and Recreation under contract no. 4-823-9081 with the California Academy of Sciences.''
  • Jennings, M.R., Hayes, M.P. and Holland, D.C. (1992). A petition to the U.S. Fish and Wildlife Service to place the California Red-legged Frog (Rana aurora draytonii) and the Western Pond Turtle (Clemmys marmorata) on the list of endangered and threatened wildlife and plants.
  • 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(6), 1287-1299.
  • Nussbaum, R. A., Brodie, E. D., Jr., and Storm, R. M. (1983). Amphibians and Reptiles of the Pacific Northwest. University of Idaho Press, Moscow, Idaho.
  • Rathbun, G.B., and Murphy, T.G. (1996). ''Evaluation of a radio-belt for ranid frogs.'' Herpetological Review, 27(4), 197-199.
  • Scott, N. and Rathbun, G. (1998). ''Essays provided to Ina Pisani in response to a working draft of California red-legged frog recovery plan.''
  • Stebbins, R. C. (1985). A Field Guide to Western Reptiles and Amphibians. Houghton Mifflin, Boston.
  • Storer, T. I. (1925). "A synopsis of the amphibia of California." University of California Publications in Zoology, 27, 1-342.
  • Storm, R.M. (1960). ''Notes on the breeding biology of the Red-legged Frog (Rana aurora aurora).'' Herpetologica, 16, 251-259.
  • U.S. Fish and Wildlife Service (2002). Recovery Plan for the California Red-legged Frog (Rana aurora draytonii). U.S. Fish and Wildlife Service, Portland, Oregon.
  • Wright, A. H. and Wright, A. A. (1949). Handbook of Frogs and Toads of the United States and Canada. Comstock Publishing Company, Inc., Ithaca, New York.
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Threats

Major Threats
Factors contributing to local declines include wetland destruction and degradation/fragmentation, urbanization, residential development, reservoir construction, stream channelization, livestock grazing of riparian vegetation, off-road vehicle activity, drought, overharvesting, and exotic fishes (bass, mosquitofish) and possibly bullfrogs (Kiesecker and Blaustein 1998; USFWS 1994, 1996, 2000; Adams 1999, 2000; Lawler et al. 1999; Cook and Jennings 2001; Kiesecker, Blaustein and Miller 2001a; Cook 2002). An important threat is the loss of wetlands in the Willamette Valley (Oregon) and Puget Lowlands (Washington), but populations remain in some urbanized areas (see Pearl, in Lannoo 2005). Conversion of habitat to more permanent ponds is an important threat (as this allows breeding waters to be invaded by non-native predators). Habitat characteristics and good leaping ability may render Rana aurora less vulnerable to bullfrog predation than is Rana pretiosa (Pearl et al. 2004). McAllister and Leonard (in Jones et al. 2005) noted that in many areas red-legged frogs coexist with bullfrogs.

Declines in the red-legged frog complex (including Rana draytonii) also have been attributed to global warming, UV-B radiation (Belden and Blaustein 2002), airborne contaminants (pesticide drift), and disease (see Davidson et al. 2001). Davidson et al. (2002) found support for the negative impact of wind-borne agrochemicals and weaker evidence for the widespread impact of habitat destruction and UV-B radiation; evidence did not support the hypothesis that declines have been caused by climate change.
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Degree of Threat: Medium

Comments: Factors contributing to local declines include wetland destruction and degradation/fragmentation, urbanization, residential development, reservoir construction, stream channelization, livestock grazing of riparian vegetation, off-road vehicle activity, drought, overharvesting, and exotic fishes (bass, mosquitofish) and possibly bullfrogs (Kiesecker and Blaustein 1998; USFWS 1994, 1996, 2000; Adams 1999, 2000; Lawler et al. 1999; Cook and Jennings 2001; Kiesecker, Blaustein and Miller 2001a; Cook 2002). An important threat is the loss of wetlands in the Willamette Valley (Oregon) and Puget Lowlands (Washington), but populations remain in some urbanized areas (see Pearl, in Lannoo 2005). Conversion of habitat to more permanent ponds is an important threat (as this allows breeding waters to be invaded by non-native predators). Habitat characteristics and good leaping ability may render Rana aurora less vulnerable to bullfrog predation than is Rana pretiosa (Pearl et al. 2004). McAllister and Leonard (in Jones et al. 2005) noted that in many areas red-legged frogs coexist with bullfrogs.

Declines in the red-legged frog complex (including Rana draytonii) also have been attributed to global warming, UV-B radiation (Belden and Blaustein 2002), airborne contaminants (pesticide drift), and disease (see Davidson et al. 2001). Davidson et al. (2002) found support for the negative impact of wind-borne agrochemicals and weaker evidence for the widespread impact of habitat destruction and UV-B radiation; evidence did not support the hypothesis that declines have been caused by climate change.

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Life History, Abundance, Activity, and Special Behaviors

Many factors are contributing to the decline of R. aurora populations, the main being habitat destruction and degradation. Introduced predators and perhaps disease have also contributed to the decline of this species (Fellers et al in press)

  • Hayes, M. P. and Krempels, D.M. (1986). ''Vocal sac variation among frogs of the genus Rana from western North America.'' Copeia, 1986(4), 927-936.
  • Hayes, M. P. and Miyamoto, M. M. (1984). ''Biochemical, behavioral and body size difference between Rana aurora aurora and R. a. draytonii.'' Copeia, 1984(4), 1018-1022.
  • Hayes, M. P. and Tennant, M. R. (1985). ''Diet and feeding behavior of the California Red-legged Frog Rana aurora draytonii (Ranidae).'' The Southwestern Naturalist, 30(4), 601-605.
  • Jennings, M. (1988). ''Natural history and decline of native ranids in California.'' Proceedings of the Conference on California Herpetology. H.F. DeLise, P.R. Brown, B. Kaufman, and B.M. McGurty, eds., Southwestern Herpetologists Society Special Publication, 1-143.
  • Jennings, M.R. and Hayes, M.P. (1985). ''Pre-1900 overharvest of California Red-legged Frogs (Rana aurora draytonii):The inducement for bullfrog (Rana catesbeiana) introduction.'' Herpetological Review, 31(1), 94-103.
  • Jennings, M.R. and Hayes, M.P. (1990). ''Final report on the status of the California Red-Legged Frog in the Pescadero Marsh Natural Preserve. Prepared for the California Department of Parks and Recreation under contract no. 4-823-9081 with the California Academy of Sciences.''
  • Jennings, M.R., Hayes, M.P. and Holland, D.C. (1992). A petition to the U.S. Fish and Wildlife Service to place the California Red-legged Frog (Rana aurora draytonii) and the Western Pond Turtle (Clemmys marmorata) on the list of endangered and threatened wildlife and plants.
  • 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(6), 1287-1299.
  • Nussbaum, R. A., Brodie, E. D., Jr., and Storm, R. M. (1983). Amphibians and Reptiles of the Pacific Northwest. University of Idaho Press, Moscow, Idaho.
  • Rathbun, G.B., and Murphy, T.G. (1996). ''Evaluation of a radio-belt for ranid frogs.'' Herpetological Review, 27(4), 197-199.
  • Scott, N. and Rathbun, G. (1998). ''Essays provided to Ina Pisani in response to a working draft of California red-legged frog recovery plan.''
  • Stebbins, R. C. (1985). A Field Guide to Western Reptiles and Amphibians. Houghton Mifflin, Boston.
  • Storer, T. I. (1925). "A synopsis of the amphibia of California." University of California Publications in Zoology, 27, 1-342.
  • Storm, R.M. (1960). ''Notes on the breeding biology of the Red-legged Frog (Rana aurora aurora).'' Herpetologica, 16, 251-259.
  • U.S. Fish and Wildlife Service (2002). Recovery Plan for the California Red-legged Frog (Rana aurora draytonii). U.S. Fish and Wildlife Service, Portland, Oregon.
  • Wright, A. H. and Wright, A. A. (1949). Handbook of Frogs and Toads of the United States and Canada. Comstock Publishing Company, Inc., Ithaca, New York.
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Management

Conservation Actions

Conservation Actions
Rana aurora occurs in many protected areas, including several small wildlife refuges in Oregon and Washington managed by the U.S. Fish and Wildlife Service and in some state refuges. Most of its range is within actively managed agricultural and forestry matrix (under the control of private owners, the Bureau of Land Management, or the U.S. Forest Service).
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Global Protection: Many to very many (13 to >40) occurrences appropriately protected and managed

Comments: Rana aurora occurs in many protected areas, including several small wildlife refuges in Oregon and Washington managed by the U.S. Fish and Wildlife Service and in some state refuges. Most of its range is within actively managed agricultural and forestry matrix (under the control of private owners, the Bureau of Land Management, or the U.S. Forest Service).

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Relevance to Humans and Ecosystems

Benefits

The red-legged frog has been used as a resource for fisheries since the the gold rush of 1849. Its frog legs are used by many humans from the region as food. Like many other amphibians, this species can be used to indicate changes in the environment such as the cleanliness of the water and the amount of vegetation in the area. It is the prey of many native animals as well as a predator of many insects and other invertebrates, therefore it is necessary in sustaining an ecological balance in thier environment.

(Jennings, 1985; USFW 1996)

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Risks

Relation to Humans

The primary impact from humans has been from direct habitat loss, especially the construction of houses, shopping centers, and roads. Much of the range of R. aurora has been historically grazed, both by dairy and by beef cattle. Cattle grazing in riparian zones causes serious damage to the vegetation, stream channel, and water quality. R. aurora may have benefited from beef cattle grazing due to the increased number of stock ponds that are maintained for the cattle. R. aurora are also threatened by a number of introduced (non-native) species, some of which are regularly introduced by humans. These include sunfish, bass, trout, mosquitofish, and bullfrogs (Fellers et al in press).

  • Hayes, M. P. and Krempels, D.M. (1986). ''Vocal sac variation among frogs of the genus Rana from western North America.'' Copeia, 1986(4), 927-936.
  • Hayes, M. P. and Miyamoto, M. M. (1984). ''Biochemical, behavioral and body size difference between Rana aurora aurora and R. a. draytonii.'' Copeia, 1984(4), 1018-1022.
  • Hayes, M. P. and Tennant, M. R. (1985). ''Diet and feeding behavior of the California Red-legged Frog Rana aurora draytonii (Ranidae).'' The Southwestern Naturalist, 30(4), 601-605.
  • Jennings, M. (1988). ''Natural history and decline of native ranids in California.'' Proceedings of the Conference on California Herpetology. H.F. DeLise, P.R. Brown, B. Kaufman, and B.M. McGurty, eds., Southwestern Herpetologists Society Special Publication, 1-143.
  • Jennings, M.R. and Hayes, M.P. (1985). ''Pre-1900 overharvest of California Red-legged Frogs (Rana aurora draytonii):The inducement for bullfrog (Rana catesbeiana) introduction.'' Herpetological Review, 31(1), 94-103.
  • Jennings, M.R. and Hayes, M.P. (1990). ''Final report on the status of the California Red-Legged Frog in the Pescadero Marsh Natural Preserve. Prepared for the California Department of Parks and Recreation under contract no. 4-823-9081 with the California Academy of Sciences.''
  • Jennings, M.R., Hayes, M.P. and Holland, D.C. (1992). A petition to the U.S. Fish and Wildlife Service to place the California Red-legged Frog (Rana aurora draytonii) and the Western Pond Turtle (Clemmys marmorata) on the list of endangered and threatened wildlife and plants.
  • 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(6), 1287-1299.
  • Nussbaum, R. A., Brodie, E. D., Jr., and Storm, R. M. (1983). Amphibians and Reptiles of the Pacific Northwest. University of Idaho Press, Moscow, Idaho.
  • Rathbun, G.B., and Murphy, T.G. (1996). ''Evaluation of a radio-belt for ranid frogs.'' Herpetological Review, 27(4), 197-199.
  • Scott, N. and Rathbun, G. (1998). ''Essays provided to Ina Pisani in response to a working draft of California red-legged frog recovery plan.''
  • Stebbins, R. C. (1985). A Field Guide to Western Reptiles and Amphibians. Houghton Mifflin, Boston.
  • Storer, T. I. (1925). "A synopsis of the amphibia of California." University of California Publications in Zoology, 27, 1-342.
  • Storm, R.M. (1960). ''Notes on the breeding biology of the Red-legged Frog (Rana aurora aurora).'' Herpetologica, 16, 251-259.
  • U.S. Fish and Wildlife Service (2002). Recovery Plan for the California Red-legged Frog (Rana aurora draytonii). U.S. Fish and Wildlife Service, Portland, Oregon.
  • Wright, A. H. and Wright, A. A. (1949). Handbook of Frogs and Toads of the United States and Canada. Comstock Publishing Company, Inc., Ithaca, New York.
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Wikipedia

Northern red-legged frog

The northern red-legged frog (Rana aurora) is a species of amphibian, whose range is the coastal region stretching from southwest British Columbia to southern Mendocino County in Northern California, and is protected in British Columbia, Oregon and California.[2] As a member of the genus Rana, this species is considered a true frog, with characteristic smooth skin and a narrow waist. This frog requires still waters for breeding, and is rarely found at any great distance from its breeding ponds or marshes.

Northern red-legged frog adults may attain a length of 8 cm (3.1 in); they have dark facial masks and single characteristic light stripes along their jawlines.[3] The northern red-legged frog has long, powerful legs well adapted to jumping. It is one of two amphibian species classified as red-legged frog, the other species being the California red-legged frog (Rana draytonii); however, the latter species is found from southern Mendocino County southerly to Baja California. In some systems of taxonomy, this species is classified as Rana aurora aurora.

Range[edit]

The northern red-legged frog is found in western Oregon, western Washington and southwestern British Columbia, including Vancouver Island.[1] In California, its range includes every coastal county from southern Mendocino County northward. While it occurs primarily in the Northern California coastal mountain ranges, it is not found above an elevation of 1200 m. It also occurs somewhat less commonly in the southern Cascade Range.[2]

Habitat[edit]

Rana aurora adults have smooth brown or reddish-brown skin with small black markings.

The still waters of ponds, marshes or stream pools are essential for northern red-legged frog breeding habitat;[4] moreover, this species of frog is considered unusually highly oriented to its aquatic habitat, with a clear preference for thickly vegetated shoreline.[5] R. aurora requires cover, since it is subject to predation by various fishes, snakes, birds, mammals, and even certain other amphibians. When this frog senses danger, it will quickly plunge to depths of one meter or more to seek safety in the benthic zone of a pond.

Adults leave the breeding pond soon after the breeding activity is concluded, and may migrate about one half kilometer to their summer locations, which are likely to be riparian zones. In the northern part of their range, adults may hibernate. Juveniles are slower to leave the breeding ponds, but also tend to find cover in riparian areas, and may readily migrate about one half kilometer by summertime. Mature R. aurora specimens prey upon terrestrial insects, but will also take small snails and crustaceans;[6] also, they will consume worms, tadpoles, small fish. and even small frogs of other species. The tadpolee are herbivorous.

Breeding[edit]

Males and females begin to move to the breeding sites as early as October, and sometimes as late as January, depending on latitude, cumulative rainfall for the season, and average temperature.[5] Typically, stable minimum temperatures of 42 to 44°F are required to induce breeding. Observations of adult migration are best made on moonlit nights with light rains. The male is thought to defend his territory, once he is in the breeding pond area, using nocturnal displays. In fact, most activity is at night, especially enhanced by periods of light rain. The actual courtship behaviors commence in January in the California part of the range, and as late as March in northerly regions. In any case, the breeding season terminates in July at the latest, and earlier in the drier locales.

Each female produces 200 to 1100 eggs per season, and attaches the egg cluster to submerged vegetation or rotting logs, characteristically seven to 15 cm below the pond surface.[3] Egg clusters are typically about 10 cm in diameter, and may disperse into an irregular form underwater. Eggs hatch in 39 to 45 days, and tadpoles require about 80 days to attain metamorphosis.[7]

Oviposition generally takes place in densely vegetated, shallow portions of wetlands with little current, and in unusual cases, egg masses have been observed in water up to 500 cm in depth. Breeding sites can be either permanent or temporary, with inundation usually necessary into June for successful metamorphosis.[6] The June date is based on Oregon conditions; in Northern California, metamorphosis occurs in late May or early June. Breeding is initiated when water temperatures exceed about 6°C (usually in January), but can be as late as March in the extreme northern part of the range.

References[edit]

  1. ^ a b Santos-Barrera et al. (2004). Rana aurora. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 5 May 2006. Database entry includes a range map and justification for why this species is considered least concern. Entry covers R. aurora.
  2. ^ a b California Wildlife, Volume I: Amphibians and Reptiles, ed. by D.C. Zeiner et al., published by the California State Department of Fish and Game, May 2, 1988
  3. ^ a b R.C. Stebbins, Amphibians and Reptiles of North America, McGraw Hill, New York (1954)
  4. ^ U.S. Department of Agriculture Northern Red-legged Frog profile (2003)
  5. ^ a b Red-legged Frog observations in the coastal ranges and development impact analysis, Lumina Technologies, Tiburon (1997)
  6. ^ a b Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo ©2005 website excepted from University of California Press
  7. ^ G.W. Calef, Natural Mortality of Tadpoles in a Population of "Rana aurora", Ecology 54:741-758 (1973)

Further reading[edit]

  • Hillis, D. M. & Wilcox, T. P. (2005): Phylogeny of the New World true frogs (Rana). Mol. Phylogenet. Evol. 34(2): 299–314. doi:10.1016/j.ympev.2004.10.007 PDF fulltext.
  • Hillis, D. M. (2007) Constraints in naming parts of the Tree of Life. Mol. Phylogenet. Evol. 42: 331–338.
  • Shaffer, H. Bradley, Gary M. Fellers, S. Randal Voss, Jeff Oliver, Greg Pauly. (2004): Species boundaries, phylogeography, and conservation genetics of the red-legged frog (Rana aurora/draytonii) complex. Molecular Ecology. 13(9): 2667-2677.
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Names and Taxonomy

Taxonomy

Comments: Shaffer et al. (2004) presented genetic evidence supporting the recognition of Rana aurora and R. draytonii as distinct species.

MtDNA data suggest that R. aurora, R. cascadae, and R. muscosa form a clade within the R. boylii species group (Macey et al. 2001).

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