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A Guide to the Amphibians
and Reptiles of California


Northern Red-legged Frog - Rana aurora

Baird and Girard, 1852
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Red-legged frogs range map
Range in California: Red & Purple
California Red-legged Frog: Orange & Purple


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One short call




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Northern Red-legged Frog Northern Red-legged Frog Northern Red-legged Frog
  Adult Male, Humboldt County  
Northern Red-legged Frog Northern Red-legged Frog Northern Red-legged Frog
Adult, Humboldt County
Northern Red-legged Frog Northern Red-legged Frog Northern Red-legged Frog
Sub-adult, Del Norte County Sub-adult, Del Norte County
Northern Red-legged Frog Northern Red-legged Frog Northern Red-legged Frog
Adult, Del Norte County © Alan Barron Adult, Humboldt County
© Andrew Harmer
Adult, Del Norte County © Alan Barron
  Northern Red-legged Frog  
  Adult, Mendocino County
© Mike Spencer
 
     
Northern Red-legged Frogs From Outside California
Northern Red-legged Frog Northern Red-legged Frog Northern Red-legged Frog
  Adult, Pacific County, Washington  
Northern Red-legged Frog Northern Red-legged Frog Northern Red-legged Frog
Sub-adult, Multnomah County, Oregon Sub-adult, Multnomah County, Oregon
Northern Red-legged Frog Northern Red-legged Frog Northern Red-legged Frog
Sub-adult, Multnomah County, Oregon Sub-adult, Multnomah County, Oregon Adult, Multnomah County, Oregon
  Northern Red-legged Frog  
  Juvenile, 900 ft.,
Lewis County, Washington
 
     
Breeding, Eggs, and Young
Northern Red-legged Frog Northern Red-legged Frog Northern Red-legged Frog
Adult male and female in amplexus, Humboldt County © Maureen Krinsky Breeding adult male, Humboldt County.
Left: throat with very reduced vocal sacs.
Right: the same frog calling underwater on the bottom of an artificial pond about 12 inches below the surface.
Northern Red-legged Frog Northern Red-legged Frog Northern Red-legged Frog
Egg mass Tadpole eyes are set in from the margin of the head. Compare with P. regilla Mature Tadpole
Northern Red-legged Frog Northern Red-legged Frog  
Transforming tadpole Tiny metamorph, fewer than
two weeks out of the water.
 
     

You can see more pictures of Northern Red-legged Frog eggs, tadpoles and juveniles Here.

Comparison with Sympatric Foothill Yellow-legged Frog
comparison comparison  
Adult Rana aurora on left.
Adult Rana boylii on right.
(Foothill Yellow-legged Frog)
Linn County, Oregon
Adult Rana aurora on left.
Adult Rana boylii on right.
(Foothill Yellow-legged Frog)
Linn County, Oregon
 
     
Habitat
dunn's salamander habitat Northern Red-legged Frog Habitat Northern Red-legged Frog Habitat
Habitat, Del Norte County Habitat, Humboldt County Habitat, Humboldt County
Northern Red-legged Frog Habitat Northern Red-legged Frog Habitat  
Habitat, temporary pools on coastal plain, Humboldt County

Breeding habitat, Del Norte County
© Alan Barron
 

You can see more pictures of this frog and its habitat on our Northwest Herps page.

Short Videos
Northern Red-legged Frog Northern Red-legged Frog Habitat Northern Red-legged Frog Habitat
A Northern Red-legged Frog on a late summer day. Northern Red-legged Frog breeding habitat with eggs in Washington. More Northern Red-legged Frog breeding habitat with eggs in Washington.
   
Description
 
Size
Adults are 1.75 to 3 inches long from snout to vent ( 4.4 - 7.6 cm).

Appearance
A medium-sized frog with a slim waist, long legs, smooth skin and webbing on the hind feet.
Ridges on the sides (dorsolateral folds) are prominent.
Legs are relatively long.
The eyes are outward oriented.
Color and Pattern
Coloring is reddish -brown or brown, gray, or olive, with small black flecks and spots on the back and sides and dark banding on the legs.
Dark blotches marking the back typically have no light coloring in the center.
There is a dark mask on the head and a stripe extending from the shoulder to the front of the upper jaw.
The hind legs and lower belly are red underneath, giving this frog its name.
On older frogs the red coloring extends onto the belly and sides.
The chest and throat are creamy and marbled with dark gray.
Yellowish-green and black coloring mottles the groin.
Male/Female Differences
Males develop enlarged forearms and a dark nuptial pad on each thumb during the breeding season.
Young
Often the coloring under the legs and lower belly is yellowish.
Larvae (Tadpoles)
Tadpoles are brown marked with small dark spots with eyes set in from the margin of the head. (Compare with P. regilla.)
Creamy white coloring flecked with small spots covers the lower body.
Rows of dorsolateral light spots may be evident running back from behind the eyes.

Life History and Behavior
Activity
Primarily diurnal.
Typically a pond frog, found in or near water, but Northern Red-legged Frogs can be wide-ranging and highly terrestrial, sometimes inhabiting damp places far from water.
In the northern part of the range and at higher elevations, adults probably hibernate during winter freezes.
Movement
Long rear legs give this frog excellent leaping ability, which it relies on to avoid predators by quickly leaping into vegetation or water.
Defense
Frogs remain immobile to avoid detection, but when a threat gets too close, they will quickly leap off into the brush or water.
Territoriality
Not considered territorial, but breeding males act aggressively with each other at breeding sites.
Egg masses are laid separately, unlike other northwestern ranid frogs such as R. cascadae and R. luteiventris where females lay their eggs on other egg masses.
Longevity
In captivity, this species is known to live to more than ten years.
Voice (Listen)
The call is a weak series of 5 - 7 notes, sounding like uh-uh-uh-uh-uh, lasting 1 - 3 seconds. Calls during the day or night, typically for only one or two weeks at a location (sometimes longer). Calls are typically made underwater and are easily missed because they are either not audible or very low in volume when heard in the air. Frogs may also call in the air where they are sometimes audible from a small distance. Listen here. According to Stebbins (2003) Rana aurora north of the Smith River in Del Norte County do not have vocal sacs, while frogs from Del Norte County south have rudimentary vocal sacs.
Diet and Feeding
Eats a wide variety of invertebrates. Typical of most frogs, the prey is located by vision, then a large sticky tongue is used to catch the prey and bring it into the mouth to eat.
Breeding
Reproduction is aquatic. 
Fertilization is external, with the male grasping the back of the female and releasing sperm as the female lays her eggs.

The reproductive cycle is similar to that of most North American Frogs and Toads. Mature adults come into breeding condition and the males call to advertise their fitness to competing males and to females. Males and females pair up in amplexus in the water where the female lays her eggs as the male fertilizes them externally. The eggs hatch into tadpoles which feed in the water and eventually grow four legs, lose their tails and emerge onto land where they disperse into the surrounding territory.

Males typically become reproductively mature at 2 years, females at 3 years of age.
Males develop enlarged forearms and a dark nuptial pad on each thumb during the breeding season.

Breeding and egg-laying occurs in vegetated shallows with little water flow in permanent wetlands and temporary pools which last long enough for tadpoles to transform.

Some sources state that breeding takes place in January and February, others as early as October with large numbers of frogs arriving in November and December in Oregon and Northern California. (I have witnessed breeding in Humboldt County as late as early March.)

Breeding lasts for only a week or two at a location. Afterwards, adults move back into nearby moist forests and riparian areas, sometimes travelling more than a thousand feet.
Eggs
Females lay an average of 530 - 830 eggs (ranging from 100 - 1,100) in a large gelationous oval cluster which is attached to vegetation beneath the water. Egg clusters are dispersed, not laid together in a communal mass.
The egg mass will eventually float to the surface.
Eggs hatch after about four weeks.
Tadpoles and Young
Tadpoles metamorphose in three to five months.
Recently-transformed juveniles often stay at the edge of their birth pond for a few days or weeks before dispersing into nearby moist dense vegetation.

Habitat
Found in humid forests, woodlands, grasslands, and streamsides with plant cover.
Most common in lowlands or foothills.
Frequently found in woods adjacent to streams.
Breeding habitat is in permanent water sources; lakes, ponds, reservoirs, slow streams, marshes, bogs, and swamps.

Geographical Range
Ranges from Mendocino County in Northern California north along the west coast through Oregon and Washington, west of the Cascades Mountains, on Vancouver Island, and along the southwestern coast of British Columbia.

Rana aurora was introduced from Washington State to Chichagof Island in Alaska in 1982. The population has successfully reproduced and spread into nearby wetlands.
See: Alaska Deptment of Fish and Game Page  &  2007 Population Status Report

A narrow range overlap with Rana draytonii (about 5 km) occurs in Mendocino County: Shaffer et. al. in research for their 2004 paper found only Rana aurora north of Big River, Mendocino County, both Rana aurora and Rana draytonii between Big River and Mills Creek, Mendocino County, and only Rana draytonii south of Mills Creek.
Elevational Range
Found at elevations from sea level to 4,680 ft. (1427 m.)

Notes on Taxonomy
Before being separated into two species, two subspecies of Rana aurora were recognized: R. a. aurora, and R. a. draytonii. Frogs in the very large area between Del Norte County and the Walker Creek drainage in Marin County were considered to be intergrades.

Schaeffer et al. in a 2004 genetics study determined that R. aurora actually consists of two species, R. aurora, and R. draytonii, whose ranges overlap only in a narrow zone in Mendocino County. R. aurora is found to be closely related to R. cascadae. Other studies, including an analysis of vocal sacs, have supported separate species status, concluding that R. aurora and R. draytonii are biologically quite different.

Conservation Issues  (Conservation Status)
No serious threats to this species have been documented, but the state regards it as a species worth monitoring. Introduced predators including American Bullfrogs, and water quality degradation could be negatively affecting the species.
Taxonomy
Family Ranidae True Frogs Rafinesque, 1814
Genus Rana True Frogs Linnaeus, 1758
Species aurora Northern Red-legged Frog

Baird and Girard, 1852
Original Description
Baird and Girard, 1852 - Proc. Acad. Nat. Sci. Philadelphia, Vol. 6, p. 174

from Original Description Citations for the Reptiles and Amphibians of North America © Ellin Beltz

Meaning of the Scientific Name
Rana - Frog - "Rana" probably mimics how the Romans heard their call.
aurora
- Latin - dawn, red - referring to the red color of the underside of the hind legs.

from Scientific and Common Names of the Reptiles and Amphibians of North America - Explained © Ellin Beltz

Alternate Names
Formerly Rana aurora aurora - Northern Red-legged Frog.

Related or Similar California Frogs
Rana boylii
Lithobates catesbeiana
Lithobates yavapaiensis
Rana draytonii
Rana pretiosa
Lithobates pipiens

More Information and References
California Department of Fish and Wildlife

AmphibiaWeb

Stebbins, Robert C., and McGinnis, Samuel M.  Field Guide to Amphibians and Reptiles of California: Revised Edition (California Natural History Guides) University of California Press, 2012.

Stebbins, Robert C. California Amphibians and Reptiles. The University of California Press, 1972.

Shaffer, H. Bradley, G. M. Fellers, S. Randal Voss, J. C. Olive and Gregory B. Pauly (2004 Species boundaries, phylogeography and conservation genetics of the red-legged frog (Rana aurora/draytonii) complex. Molecular Ecology 13(9): 2667-2677)

Stebbins, Robert C. A Field Guide to Western Reptiles and Amphibians. 3rd Edition. Houghton Mifflin Company, 2003.

Behler, John L., and F. Wayne King. The Audubon Society Field Guide to North American Reptiles and Amphibians. Alfred A. Knopf, 1992.

Powell, Robert., Joseph T. Collins, and Errol D. Hooper Jr. A Key to Amphibians and Reptiles of the Continental United States and Canada. The University Press of Kansas, 1998.

Corkran, Charlotte & Chris Thoms. Amphibians of Oregon, Washington, and British Columbia. Lone Pine Publishing, 1996.

Jones, Lawrence L. C. , William P. Leonard, Deanna H. Olson, editors. Amphibians of the Pacific Northwest. Seattle Audubon Society, 2005.

Leonard et. al. Amphibians of Washington and Oregon. Seattle Audubon Society, 1993.

Nussbaum, R. A., E. D. Brodie Jr., and R. M. Storm. Amphibians and Reptiles of the Pacific Northwest. Moscow, Idaho: University Press of Idaho, 1983.

Bartlett, R. D. & Patricia P. Bartlett. Guide and Reference to the Amphibians of Western North America (North of Mexico) and Hawaii. University Press of Florida, 2009.

Elliott, Lang, Carl Gerhardt, and Carlos Davidson. Frogs and Toads of North America, a Comprehensive Guide to their Identification, Behavior, and Calls. Houghton Mifflin Harcourt, 2009.

Lannoo, Michael (Editor). Amphibian Declines: The Conservation Status of United States Species. University of California Press, June 2005.

Wright, Albert Hazen and Anna Wright. Handbook of Frogs and Toads of the United States and Canada. Cornell University Press, 1949.


Davidson, Carlos. Booklet to the CD Frog and Toad Calls of the Pacific Coast - Vanishing Voices. Cornell Laboratory of Ornithology, 1995.
Conservation Status

The following status listings come from the Special Animals List and the Endangered and Threatened Animals List which are published by the California Department of Fish and Wildlife.


This frog is referred to as Rana aurora aurora by the California Department of Fish and Game.

Organization
Status Listing
U.S. Endangered Species Act (ESA) None
California Endangered Species Act (CESA) None
California Department of Fish and Wildlife DFG:SSC California Species of Special Concern
Bureau of Land Management
USDA Forest Service S Sensitive
 

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