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A Guide to the Amphibians
and Reptiles of California


Northern Pacific Treefrog - Pseudacris regilla

(Baird and Girard, 1852)

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

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to the other species


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Northern Pacific Treefrog Northern Pacific Treefrog Northern Pacific Treefrog
Adult, Humboldt County Adult, Humboldt County Adult male, Humboldt County
Northern Pacific Treefrog Northern Pacific Treefrog Northern Pacific Treefrog
Adult male, Humboldt County Adult male, Humboldt County Adult, Del Norte County © Allan Barron
Northern Pacific Treefrog Northern Pacific Treefrog Northern Pacific Treefrog
Adult, Del Norte County © Allan Barron

Underside of adult male, Humboldt County Enlarged Toe Pads
Northern Pacific Treefrogs From Outside California
Northern Pacific Treefrog Northern Pacific Treefrog Northern Pacific Treefrog
Adult, Pierce County, Washington Adult, Multnomah County, Oregon Juvenile, 6,000 ft.,
Deschutes County, Oregon
  Northern Pacific Treefrog  
  Adult, Snohomish County, Washington

 
Breeding Adults, Eggs, and Young
Northern Pacific Treefrog Northern Pacific Treefrog eggs Northern Pacific Treefrog tadpole
Adult male calling,
Kittitas County, Washington
Eggs, Lewis County, Washington Tadpole
northern pacific treefrog tadpole Northern Pacific Treefrog tadpole  
Mature tadpole with four legs, and developing pattern Tadpole  


Look here for more pictures of Northern Pacific Treefrog Eggs, Tadpoles, and Newly Transformed Frogs.


Habitat
Northern Pacific Treefrog Habitat Northern Pacific Treefrog Habitat Northern Pacific Treefrog Habitat
Habitat, temporary pools on coastal plain, Humboldt County Habitat, Humboldt County Habitat, Del Norte County
  Northern Pacific Treefrog sign  

More pictures of this frog and its habitat in the Northwest are available on our Northwest Herps page.


Short Videos
Northern Pacific Treefrog Sierran Treefrog  
A male Northern Pacific Treefrog calls while floating on a pond in the Cascades Mountains of Washington on a sunny Summer day. This is the two-part advertisement call.


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. This species is identical in sound and appearance to the Northern Pacific Treefrog.  
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. Pacific Treefrogs that were underground in the blast zone during the eruption of Mt. St. Helens were one of the few vertebrates to survive.

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.
Range
The range of this frog is not clear, due to the small number of specimens sampled for the study that described the species, and the lack of localities listed for this species. (see Taxonomic Notes below.) It is apparenty found along the far northwest coast of California, from Humboldt County, north through most of Oregon, into Washington, northern Idaho and Montana, and north into British Columbia, Canada.

The southern contact zone with Pseudacris sierra is unlear.

The only specific named locality for this species in the study is Clark Fork River, Missoula Co., Montana.

According to the U.S.G.S. online account, this species occurs north of southwest Oregon, and does not occur in California.
Taxonomic Notes
"We (actually the Society for the Study of Amphibians and Reptiles, the Herpetologists' League, and the American Society of Ichthyologists and Herpetologists) have decided it best to call our local loud mouths, the Pacific Treefrog, Pseudacris regilla. So, we're going to acknowledge that the species is not a treefrog, it's a chorus frog. But, we're going to concede that the vernacular doesn't have to be an accurate reflection of phylogeny and go with the traditional, well-recognized name, Pacific Treefrog."   Kelly McAllister, Washington Department of Fish and Wildlife


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 ta 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.

Pacific Treefrogs have been found in Christmas trees shipped from Washington State to Anchorage Alaska, where there is no requirement to shake the trees when they are imported to remove stowaway species. Wildlife officials in the state are suggesting that residents who find frogs bring them in or euthanize them. (Anchorage Daily News, 12/18/09.)

Taxonomy
Family Hylidae Treefrogs Laurenti, 1768
Genus Pseudacris Chorus Frogs Fitzinger, 1843
Species regilla Northern Pacific Treefrog

(Baird and Girard, 1852)
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
regilla
- Latin - regal, splendid - probably referring to the markings

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

Alternate Names
Pseudacris regilla - Northwest 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 sierra - Sierran 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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