California Reptiles & Amphibians

Rana boylii - Foothill Yellow-legged Frog, Pg. 1

Click on a picture for a larger view

Historical Range in California: Red

Listen to this frog:

A short example

More sounds of
Rana boylii

More pictures and information
from this web site:

Page 2: Eggs and Tadpoles

Oregon frogs and habitat

Watch short movies of this frog at
Endangered Species International
(www.endangeredspeciesinternational.org)

Adult, Mendocino County

Adult, Santa Clara County

Juvenile, Del Norte County

Adult, Butte County
© 2005 Jackson Shedd

Juvenile, Santa Clara County

Adult, Del Norte County
© Alan Barron

Red-backed forms, Humboldt County © Steven Krause

Juvenile, Del Norte County

Adult, Shasta County
© Michael A. Peters

Sub-adult, Shasta County © Michael A. Peters

Juvenile, Humboldt County

Adult Rana aurora on left.
(Northern Red-legged Frog)
Adult Rana boylii on right.
Linn County, Oregon

Adult Rana aurora on left.
(Northern Red-legged Frog)
Adult Rana boylii on right.
Linn County, Oregon

Small paired vocal sacs on a calling adult male, Linn County, Oregon

Egg mass, Linn County, Oregon

Tadpole, Santa Clara County

More pictures of eggs and tadpoles and breeding habitat.

Habitat

Habitat, Mendocino County

Habitat, Del Norte County

Habitat, Santa Clara County

Habitat, Humboldt County

Habitat, Santa Clara County

Short 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.

Description

Size

Adults are 1 1/2 - 3 1/5 inches long from snout to vent ( 3.8 - 8.1 cm).

Appearance

Coloring is gray, brownish, or olive, tending to match the background of its habitat. Can be plain or mottled with dark spotting. There is no mask through the eyes. Light-colored band across top of head. Underneath rear legs and lower abdomen are yellow. Underneath is whitish with dark spotting on throat and chest. Skin is grainy. Dorsolateral folds are not distinct.

Voice (Listen)

The calling of this frog is rarely heard. 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 at night and during the day mostly underwater and occasionally in the air. In the noisy stream environments where this frog breeds, underwater sounds are easier for the frogs to hear.

Behavior

Little is known about the life history of this species. It is usually found near water and is mostly active during daylight.
It dives to the bottom and hides in rocks or litter when threatened.

Diet

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

Reproduction and Young

Reproduction is aquatic. Fertilization is external. Mating and egg-laying occurs in streams and rivers (not ponds or lakes) from April until early July, after streams have slowed from winter runoff. In California, researchers (G. Fellers) have found egg masses between April 22nd and July 6th, with an average of May 3rd.

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 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.

Range

This frog originally ranged from northern Oregon west of the Cascades south along the coast to the San Gabriel Mountains, and south along the foothills of the western side of the Sierra Nevada Mountains to the Tehachapi Mountains, with an isolated population (now possibly extinct) in the San Pedro Martir Mountains of Baja California. Currently, this frog is no longer found in the San Gabriel Mountains or along the coast south of Monterey County, and the few remaining populations in the foothills of the southern Sierra Nevada Mountains are nearly extinct.

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.
From sea level to 6,700 ft. (2,040 m.)

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
Genus	Rana	True Frogs
Species	boylii	Foothill Yellow-legged Frog
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
Rana yavapaiensis Rana catesbeiana Rana draytonii Rana cascadae Rana aurora Rana pretiosa Rana pipiens Rana sierrae
More Information and References
Natureserve Explorer California Dept. of Fish and Game AmphibiaWeb Stebbins, Robert C. A Field Guide to Western Reptiles and Amphibians. 3rd Edition. Houghton Mifflin Company, 2003. Behler, John L., & F. Wayne King. The Audubon Society Field Guide to North American Reptiles and Amphibians. Alfred A. Knopf, 1992. 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, 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.

Conservation Status
The following status listings come from the Special Animals List which is published several times each year 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 Game	DFG:SSC	California Species of Special Concern
Bureau of Land Management	BLM:S	Sensitive
USDA Forest Service	USFS:S	Sensitive
Natureserve Global Conservation Status Ranks	G3 S2S3	Vulnerable
World Conservation Union - IUCN Red List	IUCN:NT	Near Threatened

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