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A Guide to the Amphibians
and Reptiles of California


Foothill Yellow-legged Frog - Rana boylii

Baird, 1854
Click on a picture for a larger view



Foothill Yellow-legged Frog
Historic Range in California: Red


Listen to this frog:

speaker
A short example


observation link



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Foothill Yellow-legged Frog Foothill Yellow-legged Frog foothill yellow-legged frog
Adult, Mendocino County Adult, Mendocino County Adult, Mendocino County
foothill yellow-legged frog foothill yellow-legged frog foothill yellow-legged frog
Adult, Santa Clara County Adult with mottled pattern, Shasta County
© Michael A. Peters
foothill yellow-legged frog foothill yellow-legged frog foothill yellow-legged frog
Adult under water, Trinity County Red-backed form, Humboldt County
© Steven Krause
Red-backed form, Humboldt County
© Steven Krause
foothill yellow-legged frog foothill yellow-legged frog foothill yellow-legged frog
Adult, Del Norte County
© Alan Barron
Adult, Del Norte County
© Alan Barron
Adult, Del Norte County
© Alan Barron
foothill yellow-legged frog foothill yellow-legged frog  
Adult, Butte County
© 2005 Jackson Shedd
Adult, Butte County
© 2005 Jackson Shedd
 
foothill yellow-legged frog foothill yellow-legged frog California Red-legged Frog
Sub-adult from Mariposa County © Christian Naventi

A California Red-legged Frog and a Foothill Yellow-legged Frog in the same creek in Santa Clara County.
© Owen Holt
   
Juveniles
foothill yellow-legged frog foothill yellow-legged frog foothill yellow-legged frog
Juvenile, Del Norte County Juvenile, Humboldt County Juvenile, Del Norte County
foothill yellow-legged frog foothill yellow-legged frog foothill yellow-legged frog
Juvenile, Santa Clara County Sub-adult, Shasta County © Michael A. Peters
foothill yellow-legged frog foothill yellow-legged frog foothill yellow-legged frog
New metamorph, Santa Clara County
© Neil Keung 
New metamorph, Santa Clara County
© Neil Keung 
New metamorph, Santa Clara County
© Neil Keung 
     
Comparison of Foothill Yellow-legged Frog and Northern Red-legged Frog
(which is similar in appearance to the California Red-legged Frog.)
foothill yellow-legged frog comp foothill yellow-legged frog comp  
Adult Rana aurora on left.
(Northern Red-legged Frog)
Adult Rana boylii on right, both from the same river in Linn County, Oregon.
Adult Rana aurora on left.
(Northern Red-legged Frog)
Adult Rana boylii on right, both from the same river in Linn County, Oregon.
 
     
Breeding, Eggs, Tadpoles
foothill yellow-legged frog foothill yellow-legged frog eggs foothill yellow-legged frog tadpoles
Small paired vocal sacs on a calling adult male, Linn County, Oregon Egg mass, Linn County, Oregon Tadpole, Santa Clara County
  foothill yellow-legged frog  
  Adult male and female in amplexus, Salmon River, Siskiyou County
 © Janjaap Dekker
 


See More pictures of eggs and tadpoles and breeding habitat.


Habitat
foothill yellow-legged frog habitat foothill yellow-legged frog habitat foothill yellow-legged frog habitat
Habitat, Mendocino County river
Habitat, Mendocino County river
Habitat, Del Norte County creek
foothill yellow-legged frog habitat foothill yellow-legged frog habitat foothill yellow-legged frog habitat
Habitat, Santa Clara County creek Habitat, Humboldt County  creek Habitat, Santa Clara County creek
foothill yellow-legged frog habitat foothill yellow-legged frog habitat foothill yellow-legged frog habitat
Habitat, Shasta County creek
© Michael A. Peters
Habitat, 1600 ft., Del Norte County
creek © Alan Barron
Habitat, Santa Clara County creek
foothill yellow-legged frog habitat foothill yellow-legged frog habitat foothill yellow-legged frog habitat
Habitat, Shasta County river
Habitat, Stanislaus County creek Habitat, Mariposa County
© Christian Naventi
foothill yellow-legged frog habitat foothill yellow-legged frog habitat  
Habitat, Trinity County creek Habitat, Mendocino County creek  
     
Short Videos
foothill yellow-legged frog video foothill yellow-legged frog video foothill yellow-legged frog video
Scenes from a Foothill Yellow-legged Frog breeding site along a river in Oregon, including calls made in the air and underwater. (The underwater calls were not recorded along with the video, they were added later, however, the frogs depicted underwater are calling male frogs.) A Foothill Yellow-legged frog calls at the edge of a small pool in a river with just its head out of the water, producing a call that can be heard in the air and underwater. The sounds heard here were recorded with an underwater microphone placed about 3 feet behind the frog. Foothill Yellow-legged frogs trying to hide by blending in with the rocks on the bottoms of several creeks in California and southern Oregon.

Watch more short movies of this frog at Endangered Species International


Description
 
Size
Adults are 1.5 - 3.2 inches long from snout to vent ( 3.8 - 8.1 cm). (Stebbins & McGinnis, 2012)

Appearance
A medium-sized frog with a slim waist, long legs, and webbing on the hind feet.
The skin is grainy rather than smooth.
Ridges on the sides (dorsolateral folds) are not distinct.
Color and Pattern
Coloring is gray, brownish, or olive, sometimes red, tending to match the background of its habitat.
Can be plain or mottled with dark spotting. Occasionally heavily mottled.
There is no mask through the eyes.
A light-colored band runs across the top of the head.
The undersides of the rear legs and lower abdomen are yellow.
The venter is whitish with dark spotting on the throat and chest.
Larvae (Tadpoles)
1.5 to 2.25 inches long (3.7 to 5.6 cm) (Stebbins & McGinnis, 2012)
Eyes are well up on the top of the head.
Color is olive-gray with coarse brown spotting.

Life History and Behavior
Activity
Little is known about the life history of this species.
It is usually found near water and is mostly active during daylight.
Defense
Dives to the bottom and hides in rocks or litter when threatened, using cryptic color and markings to blend in with the stream substrate.
Territoriality
Unknown. Adult males may defend breeding sites.
Longevity
Not known.
Voice  (Listen)
The calling of this frog is rarely heard.
The call is a faint one-note low-pitched, raspy series of 4 - 6 notes per second, made with small, paired vocal sacs.
Grunts and oinks may also be heard.

Calls are made at night and during the day mostly underwater but occasionally in the air.
In the noisy stream environments where this frog breeds, underwater sounds are easier for the frogs to hear.
Diet and Feeding
Diet consists of a wide variety of invertebrates including aquatic, terrestrial, and flying insects, spiders, snails, and grasshoppers.

Prey is located by sight, then a large sticky tongue is used to catch the prey and bring it into the mouth to eat.

Cannibalism has been observed in adult frogs which had eaten recently-metamorphosed juvenile frogs. (Herpetological Review 38(2), 2007)

Tadpoles graze the surface of rocks and vegetation to consume algae and detritus.
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.

The age at which males and females become reproductively mature is generally thought to be the second year after metamorphosis, but may be as early as six months after metamorphosis. (Fellers in Elliot et al, 2009)

Mating and egg-laying occurs exclusively in streams and rivers (not in ponds or lakes) from April until early July, after streams have slowed from winter runoff.

In California, researchers have found egg masses between April 22nd and July 6th, with an average of May 3rd.
Eggs
Grapelike clusters of eggs are laid on the downstream side of rocks in shallow slow-moving water where they are attached to submerged rocks and pebbles and occasionally vegetation.

Eggs can number from 300 - 2,000, averaging 900.
Egg masses are often covered with a layer of silt, which probably helps to hide them from predators.
Eggs hatch within 5 - 37 days, depending on water temperature.
Tadpoles and Young
Tadpoles remain around the egg mass for a about a week, then they move away to feed, using rocks and gravel for cover.
Tadpoles transform in 3 to 4 months, typically from July to October.
Newly metamorphosed juveniles typically migrate upstream from the hatching site.

Habitat
Frequents rocky streams and rivers with rocky substrate and open, sunny banks, in forests, chaparral, and woodlands. Sometimes found in isolated pools, vegetated backwaters, and deep, shaded, spring-fed pools.

Geographical Range
This frog originally ranged from northern Oregon west of the Cascades south along the coast ranges to the San Gabriel Mountains, and south along the foothills of the western side of the Sierra Nevada Mountains to the edge of the Tehachapi Mountains, with an isolated population (now possibly extinct) in the San Pedro Martir Mountains of Baja California.

Populations on the north coast and in the northern Sierra Nevada are the healthiest. Several apparently healthy populations occur in streams draining the south coast range into the Central Valley. The few remaining populations in the foothills of the southern Sierra Nevada Mountains are nearly extinct. This frog is no longer found along the coast south of Monterey County or in the San Gabriel Mountains, where some previous locations were North Fork San Gabriel River, South Fork San Gabriel River, SW of Crystal Lake Park, Mt. Wilson, Monrovia, and Claremont. There were old museum records from the San Bernardino mountains east of Running Springs, and San Diego County at Jacumba and near Banner, but it seems those specimens were misidentified. 
Elevational Range
Sea level to 6,000 ft. (1,830 m.) (Stebbins & McGinnis, 2012)

Conservation Issues  (Conservation Status)
This frog has disappeared from much of its range in California (possibly up to 45 percent.) Populations south of southern Monterey County are now apparently extinct. Extremely high water levels in 1969 may have been one cause for that decline. Rana boylii is also gone from an estimated 66 percent of its range in the foothills of the Sierra Nevada Mountains, especially south of highway 80 where it is nearly extinct. Water released from reservoirs, that washes away eggs and tadpoles and forces adult frogs away from the streams leaving them more vulnerable to predators, is a serious problem for frogs in the Sierra Nevada foothills. Air-borene pesticides from the vast agricultural fields of the Central Valley are also likely to be a primary threat. Recreational activities along streams that alter streambeds, especially gold mining, are also having a negative impact on frog populations in the Sierra foothills. Introduced fish also stress frog populations by consuming eggs and tadpoles, and introduced bullfrogs compete for food and eat the frogs. Habitat loss, disese, introduced crayfish, stream alteration from dams, mining, logging, and grazing, are also threats to this frog.
Frogs in Oregon have also undergone serious declines.
Taxonomy
Family Ranidae True Frogs Rafinesque, 1814
Genus Rana True Frogs Linnaeus, 1758
Species boylii Foothill Yellow-legged Frog

Baird, 1854
Original Description
Baird, 1854 - Proc. Acad. Nat. Sci. Philadelphia, Vol. 7, p. 62

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.
boylii - honors Boyle, C.C.

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

Alternate Names
None

Related or Similar California Frogs
Lithobates yavapaiensis
Lithobates catesbeiana
Rana draytonii
Rana cascadae
Rana aurora
Rana pretiosa
Lithobates pipiens
Rana sierrae

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.

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.



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 BLM:S Sensitive
USDA Forest Service USFS:S Sensitive
 

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