Range in California: Green
Northern Red-legged Frog: Red
Click here to see a range map of the former Rana aurora subspecies.
Listen to this frog:
A short example
iPhone App
Electronic Field Guide to the
Reptiles and Amphibians of
Southern California
Available Now at the
iTunes App Store. |
|
 |
 |
 |
 |
| |
Adult, San Mateo County |
|
 |
 |
 |
 |
Adult male, interior of the Coast Range, western Fresno County |
Adult, Marin County |
Sub-adult, Contra Costa County |
Adult, showing the red coloring underneath the legs, San Mateo County |
 |
 |
 |
 |
| |
Sub-adult, Contra Costa County |
|
 |
 |
 |
 |
| Adult, Contra Costa County. |
Adult, Marin County |
Adult, Contra Costa County |
|
|
 |
 |
 |
|
Adult, San Mateo County |
Adult, Contra Costa County. |
Adult, Contra Costa County. |
 |
 |
|
 |
| Adult, San Mateo County |
Adult, San Joaquin County.
© James Rexroth |
|
Adult, Marin County |
 |
 |
 |
 |
Adult, Alameda County |
Adult, Alameda County |
Adult, Alameda County |
Adult, Marin County |
 |
 |
 |
 |
|
|
Adult, Monterey County
© Anonymous Contributor
|
|
 |
 |
 |
 |
| Adult, Contra Costa County |
Adult , Santa Cruz County © Ruby Christine Head |
Adult male, interior of the Coast Range, western Fresno County |
 |
 |
 |
 |
|
|
Adult, Santa Barbara County
© Vince Semonsen |
Adult, Marin County |
|
|
 |
 |
These frogs, discovered by Sean Barry in Butte County in 1997, are some of the last known California Red-legged Frogs remaining in the Sierra Nevada mountains.
© Sean Barry |
Juvenile, Contra Costa County |
Juvenile, Contra Costa County |
 |
 |
|
|
Juvenile, Contra Costa County |
San Mateo County Park Sign |
|
|
Habitat |
 |
 |
 |
 |
Habitat, pond, Contra Costa County
|
Habitat, small pond, Contra Costa County
|
Habitat, pond, Contra Costa County |
Habitat, cattle pond, Contra Costa County |
 |
 |
 |
 |
Habitat, pond, San Mateo County |
Habitat, San Mateo County |
Habitat, breeding pond, Santa Lucia Preserve, Monterey County. Courtesy of David Keegan & Susan Whitford |
Habitat, breeding pond, Santa Lucia Preserve, Monterey County. Courtesy of David Keegan & Susan Whitford
|
 |
 |
 |
 |
| Habitat, coastal marsh, Marin County |
Habitat, Riverside County wetlands |
Habitat, coastal lagoon, Marin County |
 |
 |
 |
 |
Habitat, small coastal pond, Marin County, during different seasons |
Breeding pond, Contra Costa County |
 |
 |
|
|
| Habitat, Alameda County |
Habitat, small creek, Contra Costa County |
|
 |
 |
|
|
| Breeding area, Contra Costa County |
Habitat, Contra Costa County |
|
|
Short Videos
|
 |
 |
 |
 |
| A large adult California Red-legged Frog sits still at the edge of a pond under some vegetation until a grasshopper lands nearby when it explodes into action, grabbing the insect on the underside of its long sticky pink tongue. |
The same frog to the left eating grasshoppers, but this time shown in slow motion so you can see its big tongue in action. |
Red-legged frogs around a couple of small ponds in July. |
Red-legged frogs around a small pond in August. |
 |
 |
 |
|
| Two male California Red-legged Frogs are seen here in a Contra Costa County pond in March in amplexus with California Toads (possibly females.) Male toads attempt to wrestle the frogs off their prospective mates. When they grab the frogs, the frogs give their low chuckling release call, while the toads make their peeping release call. The video also starts and ends with the frog release calls. |
A bunch of juvenile California Red-legged Frogs sit around on a sunny summer afternoon in a pond in Contra Costa County. |
Adult frogs sitting around in ponds in Contra Costa and Marin Counties. |
|
|
Description |
Size |
| 1 3/4 - 5 1/4 inches ( 4.4 - 13.3 cm.) |
| Appearance |
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 on the back, typically have 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 eyes are outward oriented. The hind legs 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. Toes are not completely webbed. Legs are relatively long. Dorsolateral folds are prominent.
Tadpoles are brown marked with small dark spots with eyes set in from the margin of the head. Creamy white coloring flecked with small spots covers the lower body. Eyes are set in from the margin of the head. Compare with P. regilla. |
| Voice (Listen) |
| The call is a weak series of 5 - 7 notes, sounding like uh-uh-uh-uh-uh, lasting 1 - 3 seconds. After the series there is sometimes a last note which is similar to a growl or groan. The calls are made during the day or at night in the air and underwater and are easily missed. Calling lasts only one to two weeks at a location. Rana draytonii south of San Francisco have paired vocal sacs. Frogs north to Del Norte County, including Rana aurora, have rudimentary vocal sacs. |
| Behavior |
| Primarily diurnal. Typically a pond frog, found in or near water, but can wander overland at times, sometimes found in damp places far from water, including cool and moist bushes and thickets. Frogs remain immobile to avoid detection, but when a threat gets too close, they will quickly leap off into the brush or water. Found active all year except in wetlands that dry out in summer, where frogs will estivate in moist refuges until the late fall rains. |
| Diet |
Diet consists of a wide variety of invertebrates, and occasionally small vertebrates such as fish, mice, frogs and salamander larvae. 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.
Tadpoles probably feed on algae, diatoms, and detritus by grazing the surface of rocks and plants. |
| Reproduction and Young |
Reproduction is aquatic. Fertilization is external. Mating and egg-laying occurs in permanent and temporary bodies of water - mostly ponds, but also marshes, lagoons, and slow-moving parts of streams. Breeding occurs from late November to April, depending on the location, and lasts for only a week or two.
Some adults inhabit the breeding pond all year, but other frogs disperse into other habitats and must travel overland some distance, usually on rainy nights, to get to the breeding pond. Males develop enlarged forearms and a dark nuptial pad on each thumb during the breeding season.
Females lay from 300 - 4,000 eggs (average 2,000) in a large gelationous cluster which is attached to plants near the water surface. Eggs hatch after about four weeks. Tadpoles metamorphose in four to seven months, but at some sites they overwinter and metamorphose the following summer. |
| Range |
Endemic to California and northern Baja California. Historically, this species was found along the coast and Coast Ranges from Mendocino County in northern California south to northern Baja California, and inland east through the northern Sacramento Valley into the foothills of the Sierra Nevada mountains, south to Tulare county, and possibly Kern county.
They probably did not occur in the central vallley due to annual floods.
A narrow range overlap with Rana aurora 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. |
| Habitat |
Found mainly near ponds in humid forests, woodlands, grasslands, coastal scrub, and streamsides with plant cover. Most common in lowlands or foothills. Frequently found in woods adjacent to streams. Breeding habitat is in permanent or ephemeral water sources; lakes, ponds, reservoirs, slow streams, marshes, bogs, and swamps.
Ephemeral wetland habitats require animal burrows or other moist refuges for estivation when the wetlands are dry.
From sea level to 5,000 ft. (1,525 m.) |
| Taxonomic Notes |
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.
Before being split 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. |
| Conservation Issues (Conservation Status) |
Populations in the Sierra Nevada Mountains and in southern California have declined seriously possibly due to introductions of non-native predators such as American Bullfrogs and fish, habitat loss due to development and agriculture, and pesticide pollution. Windborne pollutants from agriculture in the Central Valley have probably contributed considerably to the extirpation of the species in the nearby Sierra Nevada foothills. Much of this frog's prime habitat of foothills grassland has been destroyed by develoment in the Bay Area and in the Sierra Nevada foothills. The role of the Chytrid fungus and of the introduced bullfrog in Rana draytonii declines are not well understood.
As of 2009, only six recently-discovered populations are known in the Sierra Nevada, and these were all discovered after 1997. Only two very small extant populations are known from South of Santa Barbara, one on the Santa Rosa Plateau in Riverside County, and one in Ventura County. The species apparently persists in northern Baja California.
In the fall of 2010, the Placer Land Trust partnered with Westervelt Ecological Services to permanently protect the Big Gun Preserve, 52 acres of mixed conifer woodlands, chaparral, and riparian corridors, located in the Middle Fork American River watershed, which contains the largest remaining Sierra Nevada population of California Red-legged Frogs.
A 2009 study* has documented male Rana draytonii in amplexus with juvenile American Bullfrogs and has proposed that this causes reproductive interference by the invasive species which could cause a reduction in the population growth rate of Rana draytonii since these males no longer call to attract females which causes fewer females to attempt to breed at the site, and because males engaged in amplexus are at greater risk of predation. And it raises the possibility that male Rana draytonii will find the smaller female Rana draytonii unattractive, leaving them without mates. This preference by the males leads them into an "evolutionary trap."* D'Amore, Antonia, Erik Kirby and Valentine Hemingway. Reproductive Interference By An Invasive Species: An Evolutionary Trap? Herpetological Conservation and Biology 4(3):325-330. Submitted: 2 September 2008; Accepted: 9 November 2009. |
|
|
Taxonomy |
| Family |
Ranidae |
True Frogs |
| Genus |
Rana |
True Frogs |
| Species |
draytonii |
California Red-legged Frog
|
|
Original Description |
Rana aurora - 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.
draytonii - honors Drayton, Joseph
from Scientific and Common Names of the Reptiles and Amphibians of North America - Explained © Ellin Beltz
|
|
Alternate Names |
Formerly Rana aurora draytonii - California Red-legged Frog
|
|
Related or Similar California Frogs |
Rana aurora
Rana boylii
Lithobates catesbeiana
Rana cascadae
|
|
More Information and References |
Natureserve Explorer
California Dept. of Fish and Game
AmphibiaWeb
Center for Biological Diversity
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., 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.
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.
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, Anna. 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.
Jones, Lawrence L. C. , William P. Leonard, Deanna H. Olson, editors. Amphibians of the Pacific Northwest. Seattle Audubon Society, 2005.
|
|
|
|
The following status listings come from the Special Animals List which is published by the California Department of Fish and Wildlife.
This frog is referred to as Rana aurora draytonii on the Special Animals List.
|
Organization
|
Status Listing
|
| U.S. Endangered Species Act (ESA) |
FT |
Threatened |
| 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 |
|
|
| Natureserve Global Conservation Status Ranks |
G4T2T3 S2S3 |
Apparently Secure |
World Conservation Union - IUCN Red List
|
IUCN:VU |
Vulnerable |
|
|
|
