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A Guide to the Amphibians
and Reptiles of California


Sierran Treefrog - Pseudacris sierra

(Jameson, Mackey, and Richmond, 1966)

(=Pseudacris sierra - Pacific Chorus Frog &  =Pseudacris [Hyla] regilla - Pacific Treefrog)
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California Treefrogs Range Map
Approximate Range in
California
: Green

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Sierran Treefrog Sierran Treefrog Sierran Treefrog Sierran Treefrog
Adult male, San Mateo County Adult, Butte County Adult, Contra Costa County Sub-adult, Mendocino County
Sierran Treefrog Sierran Treefrog Sierran Treefrog Sierran Treefrog
Adult, Alameda County Adult, Stanislaus County 
Sierran Treefrog Sierran Treefrog Sierran Treefrog Sierran Treefrog
Calaveras County, © Diane Morrow Adult, Alameda County Adult male, Contra Costa County
Sierran Treefrog Sierran Treefrog Sierran Treefrog Sierran Treefrog
Adult, 9000 ft. Sierra Nevada Mountains, Tuolumne County  Adult, Siskiyou Mountains,
Siskiyou County
Adult, Butte County
© Jackson Shedd
Adult, Butte County
© Mela Garcia
Sierran Treefrog Sierran Treefrog Sierran Treefrog Sierran Treefrog
Adult, Mariposa County. © Dr. Jean K. Krejca, Zara Environmental LLC Sub-adult, Monterey County
© Carla England
Adult, Nevada County © Maxine Adult, Lassen County © Debbie Frost
Sierran Treefrog Sierran Treefrog Sierran Treefrog Sierran Treefrog
Adult, just after jumping into the water, Contra Costa County Adult, Contra Costa County Adult, Sutter Buttes, Sutter County.
© Jackson Shedd.
Specimen courtesy of Eric Olson.
Swimming adult, Contra Costa County
Sierran Treefrog Sierran Treefrog Sierran Treefrog  
Adult frogs of assorted colors found above a door in Lassen County © Debbie Frost Enlarged toe pads typical of Treefrogs.  
Sierran Treefrog northern pacific rattlesnake habitat    
Sierran Treefrogs wander away from water after the breeding season. This one wandered up to the top of this rocky fire lookout at 6,700 ft. elevation in Sierra County where it was found in late July.  © Michael Gates

   
Sexual Dimorphism
Sierran Treefrog Sierran Treefrog Sierran Treefrog  
Adult female, showing light-colored skin under throat, Contra Costa County

Adult male, showing dark-colored skin under throat,
Contra Costa County
 
Juveniles
Sierran Treefrog Sierran Treefrog Sierran Treefrog Sierran Treefrog
After undergoing metamorphosis from a tadpole to the adult form, juveniles usually hang around the edge of their birth pond or creek. Often you can see hundreds of them hopping around. These tiny Contra Costa juveniles are only about half an inch in length. Recently transformed juvenile,
San Mateo County
Sierran Treefrog Sierran Treefrog Sierran Treefrog Sierran Treefrog
A pink and blue Juvenile, Yolo County
© Lori Grennan

Thousands of these tiny metamorphs were seen around a small pond in Siskiyou County in August.
Deformities
Because of their thin permeable skin, amphibians are one of the first indicators of environmental disturbances, some of which can cause malformations as we see below.
Sierran Treefrog Sierran Treefrog Sierran Treefrog  
This recently-metamorphosed juvenile from Contra Costa County has a rear leg deformity that is most likely caused by a parasite that is hosted by a snail before it attaches itself to a tadpole. Such deformities are becoming more common and researchers are trying to determine if there are environmental factors which are favoring the parasites or which make the frogs more susceptible to them.

This juvenile treefrog from San Mateo County has a deformed fifth leg.
© Rory Doolin.
 
Breeding Season
Sierran Treefrog Sierran Treefrog Sierran Treefrog Sierran Treefrog
Calling adult male, Contra Costa County Calling adult male, Contra Costa County Calling adult males, Contra Costa County Calling male with extended throat sack, Alpine County
Sierran Treefrog Sierran Treefrog Sierran Treefrog Sierran Treefrog
Calling male, Alpine County Calling Male, Contra Costa County Calling Male, Alameda County Adults in amplexus, Santa Clara County.
© Bill Stagnaro
Sierran Treefrog Sierran Treefrog eggs Sierran Treefrog tadpole  
Two males amplexing a female, Fresno County © Julie Nelson Eggs, Butte County Tadpole, Contra Costa County  

See more pictures of Sierran Treefrog eggs and tadpoles Here

Habitat
Sierran Treefrog Habitat Sierran Treefrog Habitat Sierran Treefrog Habitat Sierran Treefrog Habitat
Habitat, Contra Costa County Habitat, Contra Costa County Habitat, Alameda County Habitat, Butte County
Variegated Skink Habitat Sierran Treefrog Habitat Sierran Treefrog Habitat Sierran Treefrog Habitat
Habitat, 500 ft, western
Stanislaus County
Habitat, San Mateo County Habitat, Contra Costa County

Habitat in breeding season, 8,800 ft., Alpine County
Sierran Treefrog Habitat Sierran Treefrog Habitat Sierran Treefrog Habitat Sierran Treefrog Habitat
Habitat, Monterey County Habitat, Mendocino County Habitat, 4,500 ft.,
Kern County
High-altitude wet meadow habitat,
9,000 ft, Sierra Nevada mountains,
Tuolumne County
Sierran Treefrog Habitat Sierran Treefrog Habitat Sierran Treefrog Habitat Sierran Treefrog Habitat
Habitat, 6,000 ft. Siskiyou County. Habitat, flooded roadside above Klamath River, Siskiyou Mountains, Siskiyou County Habitat, 6500 ft., Warner Mountains, Modoc County Habitat, in spring during breeding season, 4,500 ft. Siskiyou County
Sierran Treefrog Habitat Sierran Treefrog Habitat Sierran Treefrog Habitat tiger salamander habitat
Breeding habitat, roadside ditch next to creek, 1,100 ft. Fresno County.

Habitat, San Mateo County Seasonal pond used for breeding,
Contra Costa County.
Follow this link to see more pictures of this pond as it looked in different months
(of different years) showing how the pond and its surroundings change over the seasons.

Short Videos
Sierran Treefrog Sierran Treefrog Sierran Treefrog Sierran Treefrog
Three adult male Sierran Treefrogs make their advertisement call one afternoon in early March in Contra Costa County. In this short video we see three adult male Sierran Treefrogs make their encounter call. These calls were elicited by making a raspy noise near the frogs as they were sitting on the water in calling position. The call of each frog is slightly different. A male Sierran Treefrog makes a few advertisement calls, until a second frog between him and the camera, makes a raspy trilled encounter call. The first frog responds with his encounter call, but when the second frog continues, he then turns to face his aggressor and charges toward him, continuing to make his encounter call. The second frog changes his call to a faster one part call. Finally they both stop, and the first frog sucks in his throat sac and dives underwater. An adult male Sierran Treefrog makes a one-part call while floating on the water on a sunny afternoon in Contra Costa County.
Sierran Treefrog Sierran Treefrog Sierran Treefrog Sierran Treefrog
A male Sierran Treefrog makes the one-part or enhanced call from the edge of a small temporary snow-melt pond at 8,600 feet elevation in Alpine County. In this video we zoom out from a calling Sierran Treefrog to show an overview of his habitat in Contra Costa County. Thousands of recently-metamorphed Sierran treefrogs surround a tiny pond in the mountains of Siskiyou County. Recently-transformed Sierran treefrogs around the shores of their birth ponds.
Description
 
Size
Adults are 3/4 - 2 inches long from snout to vent (1.9 - 5.1 cm).
Appearance
A small treefrog with a large head, large eyes, a slim waist, round pads on the toe tips, limited webbing between the toes, and a wide dark stripe through the middle of each eye that extends from the nostrils to the shoulders. Legs are long and slender. Skin is smooth and moist. Often there is a Y-shaped marking between the eyes. Dorsal body coloring is variable: green, tan, brown, gray, reddish, cream, but it is most often green or brown. The body color and the dark eye stripe do not change, but the body color can quickly change from dark to light, and dark markings on the back and legs can vary in intensity or disappear in response to environmental conditions. The underside is creamy with yellow underneath the back legs. The male's throat is darkened and wrinkled.

Tadpoles are up to 1 7/8 inches long ( 4.7 cm) blackish to dark brown and light below with a broze sheen. The intestines are not visible. Viewed from above, the eyes extend to the outline of the head.
Life History and Behavior
Active both day and night, becoming mostly nocturnal during dry periods. During wet weather, they move around in low vegetation. In locations at low elevations where temperatures are more moderate, frogs may be active all year. At colder or hotter locations, frogs avoid temperature extremes by hibernating in moist shelters such as dense vegetation, debris piles, crevices, mammal burrows, and even human buildings.

Despite the name, this frog is chiefly a ground-dweller, living among shrubs and grass typically near water, but occasionally it can also be found climbing high in vegetation. Its large toe pads allow it to climb easily, and cling to branches, twigs, and grass.

When disturbed, this frog typically hops a large distance or jumps into the water and swims into vegetation to hide. But at times they will use their cryptic body color to avoid predation by remaining motionless.

Green body color absorbs more solar radiation which can be more beneficial in cold and aquatic habitats. Brown body color absorbs less solar radiation, which may be more beneficial in drier, hotter, more terrestrial habitats.
Voice (Listen)
Advertisement calls are heard during the evening and at night, and during the daytime at the peak of the breeding season. Males produce two different kinds of advertisement calls: a two-parted, or diphasic call, typically described as rib-it, or krek-ek, with the last syllable rising in inflection, and a one-part, or monophasic call, also called the enhanced mate attraction call. They also produce a slow trilled encounter call, a release call, and a land call, which is a prolonged one-note sound that is produced much of the year, especially during rains.

The most commonly heard frog in its range.
(The call of the Baja California Treefrog is known throughout the world through its wide use as a nighttime background sound in old Hollywood movies, even those which are set in areas well outside the range of this frog. The call of the Baja California Treefrog is identical to that of the Sierran Treefrog and the Northern Pacific Treefrog and it is possible that the calls of any of these species were used as movie sound effects.)
Diet
Eats a wide variety of invertebrates, primarily on the ground at night, including a high percentage of flying insects. During the breeding season, they also feed during the day. Typical of most frogs, prey is located by vision, then the frog lunges with a large sticky tongue to catch the prey and bring it into the mouth to eat.
Tadpoles are suspension feeders, eating a variety of prey including algaes, bacteria, protozoa and organic and inorganic debris.
Reproduction and Young
Breeding is aquatic. Fertilization is external. Breeding and egg-laying occurs between November until July, depending on the location. Adults probably become reproductively mature in their first year. Males move to breeding waters and begin to make their advertisement call. These calls attract more males, then eventually females. Males call while in or next to water at night, and during daylight during the peak of breeding when calling can occur all day and night. Some males and females have been observed staying only a few weeks at a breeding site. Some males have been observed moving to another site. And others have been observed staying at a site the entire breeding season.
Males are territorial during the breeding season, establishing territories that they will defend with an encounter call or by physically butting and wrestling with another male. Satellite male breeding behavior has been observed - a silent male will intercept and mate with females that are attracted to the calling of other territorial males.

Breeding locations include slow streams, permanent and seasonal ponds, reservoirs, ditches, lakes, marshes, shallow vegetated wetlands, wet meadows, forested swamps, potholes, artificial ponds, and roadside ditches. The Baja California Treefrog tends to avoid large lakes or streams with very cold water.

Females lay on average between 400 - 750 eggs in small, loose, irregular clusters of 10 - 80 eggs each. Egg clusters are attached to sticks, stems, or grass in quiet shallow water. The eggs hatch in two to three weeks. Eggs appear to be resistant to the negative effects of solar UV-B radiation and even to increased water acidification. Eggs can also survive freezing temperatures for a short time.

Tadpoles aggregate for thermoregulation and to avoid predation. Tadpoles metamorphose in about 2 to 2.5 months, generally from June to late August. In summer, there are often large congregations of new metamorphs along the banks of breeding pools. Metamorphosed juveniles leave their birth pond soon after transformation, dispersing into adult habitats.
Habitat
This species utilizes a wide variety of habitats, often far from water outside of the breeding season, including forest, woodland, chaparral, grassland, pastures, desert streams and oases, and urban areas.
From sea level to high into the mountains (possibly to nearly 11,600 ft. (3,540 m.))
Range
The range of this frog is not clear, due to the small number of specimens sampled for the study that described the species. (see Taxonomic Notes below.) It is apparenty found from Santa Barbara County north, north of Bakersfield, and east into most of Nevada, southeast Oregon, Idaho, and part of Montana.

The southern contact zone with Pseudacris hypochondriaca and northern contact zone with Pseudacris regilla, are unlear. How far south it ranges into the southern San Joaquin Valley, the southern Sierra Nevada Mountains, and the northern Owens Valley is unclear.

According to the U.S.G.S. online account, this species occurs north into southwest Oregon.


Specific named localities are:

San Luis Obispo County, Los Padres National Forest
San Luis Obispo County, Santa Margarita
Monterey County, McClusky Slough
Shasta County, Shingleton (Shingletown)
Alpine County, Highland Lakes
Tuolumne County, Kennedy Meadows
Missoula Co., Montana, Clark Fork River

Taxonomic Notes
The naming of this frog has been confusing for years, and in 2006 it got even more confusing when one species of frog was split into three species.

In Phylogeography of Pseudacris regilla (Anura: Hylidae) in western North America, with a proposal for a new taxonomic rearrangement 2006 Molecular Phylogenetics and Evolution 39: 293-304, Ernesto Recuero, Íñigo Martínez-Solano, Gabriela Parra-Olea, and Mario García-París present evidence that Pseudacris regilla as it is currently recognized is made up of 3 species, all of which occur in California. However, they assigned names to two of the species which they later determined were incorrect. The three species were correctly named in a followup paper:

Recuero, Ernesto, Íñigo Martínez-Solano, Gabriela Parra-Olea, Mario García-París. Corrigendum to ‘‘Phylogeography of Pseudacris regilla (Anura: Hylidae) in western North America, with a proposal for a new taxonomic rearrangement’’ [Mol. Phylogenet. Evol. 39 (2006) 293–304]  
Molecular Phylogenetics and Evolution. 41(2): pp. 511.


The names they gave these three species are:


Pseudacris regilla - Northwest Chorus Frog

This is the northern clade, ranging along the north coast from approximately Humboldt County north into parts of Oregon and Washington.

Pseudacris sierra - Pacific Chorus Frog

This is the central clade, ranging approximately from Humboldt County south to Santa Barbara, and east into the Sierras, and the Northcentral, and Northeast part of the state, including Shasta County, and into Nevada, Eastern Oregon, Idaho and Montana.

Pseudacris hypochondriaca - Baja California Chorus Frog

This is the southern clade, ranging approximately from Santa Barbara south throughout Baja California, east to Bakersfield, Beatty, and southern Inyo County. This species is comprised of two subspecies, P. h. curta, which occurs in Baja California, and P. h. hypochondriaca, which occurs in California.


The SSAR (whose names are used on this website) has renamed the common names to conform to its taxonomy:

Pseudacris hypochondriaca - Baja California Treefrog

Pseudacris regilla - Northern Pacific Treefrog

Pseudacris sierra - Sierran Treefrog


And the CNAH, another major source of reptile and amphibian taxonomy, has also renamed the common names in order to conform to its taxonomy:

Pseudacris hypochondriaca - Baja California Chorus Frog

Pseudacris regilla - Pacific Chorus Frog

Pseudacris sierra - Sierra Chorus Frog



The authors, Recuero, Martínez-Solano, Parra-Olea, and García-París, do not provide detailed maps or descriptions of the ranges of the three species and they do not describe the contact zones between the species. They also do not provide any locality information for P. regilla, leaving the reader to consult previous work on the former subspecies Pseudacris regilla pacifica. This makes it hard to determine where these species occur in the state.

The dark spots on the following map are the approximate localities of the small sample of specimens used in the study. The colored areas are a guess at the range of each species. According a range map put online by the U.S.G.S., P. regilla does not even occur in California, but I have included it on my map because I believe the old subspecies P. r. pacifica ranged south along the north coast to Humboldt County, though I have no reference yet to back that up. It is possible that the species does not occur in California. Obviously, much more research is needed on these three species.

Conservation Issues  (Conservation Status)
This species is not considered to be declining in population. Tadpoles are sensitive to nitrites and excess nitrite concentrations from agricultural runoff could cause them harm.

Taxonomy
Family Hylidae Treefrogs Laurenti, 1768
Genus Pseudacris Chorus Frogs Fitzinger, 1843
Species sierra Sierran Treefrog

(Jameson, Mackey, and Richmond, 1966)
Original Description
Hyla or Pseudacris regilla (Baird and Girard, 1852) - Proc. Acad. Nat. Sci. Philadelphia, Vol. 6, p. 174

Recuero, Martinez-Solano, Parra-Olea, and García-París, 2006

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

Meaning of the Scientific Name
Pseudacris - Greek - pseudes false, deceptive and Greek - akris locust - means "false Acris" with reference to genus Acris
sierra
- refers to the Sierra Nevada Mountains

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

Alternate Names
Pseudacris sierra - Pacific Chorus Frog

Hyla regilla
- Pacific Treefrog

Pseudacris regilla
- Pacific Chorus Frog

Pseudacris regilla - Pacific Treefrog

Related or Similar California Frogs
Pseudacris hypochondriaca - Baja California Treefrog

Pseudacris regilla - Northern Pacific Treefrog

More Information and References
U. S. Geological Survey (With maps and information about the 3 species split of the former Pseudacris regilla species.)

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, 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 and the Endangered and Threatened Animals List which are published by the California Department of Fish and Wildlife.


This frog is not included on the Special Animals List, meaning there are no significant conservation concerns for it in California according to the Dept. 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 None
Bureau of Land Management None
USDA Forest Service None
 

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