Pseudacris regilla
Pseudacris regilla
(Northern Pacific Treefrog)
Native Transplant
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Pseudacris regilla (Baird and Girard, 1852)

Common name: Northern Pacific Treefrog

Taxonomy: available through www.itis.govITIS logo

Identification: Pseudacris regilla is a small hylid (treefrog) with a SVL (snout-vent length) of 19-50 mm (0.75-2 in) and small toe pads (disks) (Stebbins, 2003). The dorsal coloration of these color-changing, sometimes mottled, frogs also varies genetically:  green, reddish, tan, gray, brown, or black, but typically green or shades of brown (Leonard et al., 1993; Stebbins, 2003). A black or brown eyestripe is often present (Powell et al., 1998; Stebbins, 2003). Distinct morphological criteria for distinguishing P. regilla from its sister species the Sierran Treefrog, P. sierra, have not yet been established. See the species account titled “Pseudacris sierra (Jameson, Mackey, and Richmond, 1966)” on this website. The Northern Pacific Treefrog’s call is a stereotypical, loud, two-part “krec-ek” or “ribbit” that is probably nearly identical to the call of P. sierra.  The tadpoles of P. regilla are light greenish gray or olive brown, have high tail fins, and the internal viscera can be seen ventrally (Stebbins, 2003; Gregory and Campbell, 1984).

Northern Pacific Treefrogs have been illustrated by a variety of authorities (Test, 1898; Wright and Wright, 1949; Stebbins, 1985, 2003; Smith, 1978; Behler and King, 1979; Nussbaum et al., 1983; Cook, 1984; Gregory and Campbell, 1984; Kricher, 1993; Leonard et al., 1993; Beltz, 2005).

Size: SVL is 19-50 mm.

Native Range: Pseudacris regilla is indigenous to Pacific and western regions of North America, from southern and western British Columbia (including Vancouver Island and smaller offshore islands), Canada, southward through Washington, and western Oregon (Test, 1898; Stebbins, 1954, 2003; Jameson et al., 1966; Campbell et al., 1982; Nussbaum et al., 1983; Cook, 1984; Gregory and Campbell, 1984; Leonard et al., 1993; Lamar, 1997; Duellman and Sweet, 1999; Ripplinger and Wagner, 2004; Recuero et al., 2006a; Dornburg and Weaver, 2007).

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Nonindigenous Occurrences: In 1991, Waters (1992) collected and observed nonindigenous P. regilla from a muskeg pond adjacent to the Ward Creek Recreation Area, northwest of Ketchikan, on Revillagigedo Island, Alexander Archipelago, Alaska. This species was again observed breeding at this same site in 1992, 1993, and 1994 (Waters et al., 1998).

Pseudacris regilla was spotted in Arizona in 1995 (Howland, 1996).

Individuals were collected in Clark Fort, Kootenai, Bitterroot River, and Flathead River drainages in Montana in 2004 (Werner et al., 2004).

In Canada, Pseudacris regilla found at Eutsuk Lake (Stebbins, 1985) and Queen Charlotte Islands (Gregory and Campbell, 1984), British Columbia, are nonindigenous.

Means of Introduction: Stebbins (1985) did not describe how P. regilla were introduced to Eutsuk Lake and more recently excludes them (Stebbins, 2003), but elsewhere in British Columbia, Canada, the son of a resident of Graham Island, Queen Charlotte Islands, released a jar of tadpoles collected from Vancouver Island (Gregory and Campbell, 1984).

In 1960, E. DeBoer released tadpoles and small transformed northern Pacific chorus frogs at the muskeg pond on Revillagigedo Island, Alaska; the very same locality in which they are currently found (Waters et al., 1998).

Status: Nonindigenous Northern Pacific Treefrogs are extirpated from Eutsuk Lake (Stebbins, 2003) but established on Queen Charlotte Islands, British Columbia, Canada (Gregory and Campbell, 1984; Stebbins, 1985). They do not seem to be extremely invasive.

The P. regilla on Revillagigedo Island, Alaska, are established but have remained confined to the same muskeg pond to which they were introduced for more than 30 years (Waters et al., 1998; Stebbins, 2003). They are not invasive.

Impact of Introduction: Nonindigenous P. regilla established populations in British Columbia, Canada, have not spread far and it is not clear if they have had an impact at these northerly extremes of this frog’s range.

Alaska has a very limited number of amphibian species (Hodge, 1976), and only Taricha granulosa, the rough-skinned newt, breeds in the same muskeg pond as the nonindigenous P. regilla (Waters et al., 1998).  Since these two species are sympatric in other parts of North America (Nussbaum et al., 1983; Stebbins, 1985), and the P. regilla have remained confined to this same pond for more than 30 years, it seems doubtful that there will be an impact caused by these introduced frogs or at least not beyond the confines of their single breeding pond.

Remarks: The taxonomy of the P. regilla complex has been reviewed or summarized by numerous authors (Test, 1898; Jameson et al., 1966; Case et al., 1975; Frost, 1985, 2000, 2007; Collins and Taggart, 2002; Crother et al., 2003; Ripplinger and Wagner, 2004; Faivovich et al., 2005; Frost et al., 2006, 2008; Recuero et al., 2006a, b).   Recuero et al. (2006a) revised, and then corrected (Recuero et al. 2006b), the Pacific chorus frog complex by splitting it into three species: P. hypochondriaca, P. sierra, and P. regilla (Frost et al., 2008). See the species accounts titled “Pseudacris hypochondriaca (Hallowell, 1854)” and “Pseudacris sierra (Jameson, Mackey, and Richmond, 1966)” on this website. The natural history and biology of P. regilla and its sister species P. sierra are summarized by Wright and Wright (1949), Nussbaum et al. (1983), Leonard et al. (1993), Stebbins and Cohen (1995), and Stebbins (2003).  Scientific and standard English names follow Crother (2008).

Pseudacris regilla frequents a variety of habitats and elevations, from sea level to mountains, from grasslands to forests, and farmlands (Kricher, 1993; Leonard et al., 1993; Stebbins, 2003). This adaptable hylid is chiefly a terrestrial, nonclimber, preferring to remain among low plants near or along water (Leonard et al., 1993; Stebbins, 2003). They breed and lay their eggs in a variety of waters including marshes, ponds, lakes, reservoirs, slow streams, and roadside ditches (Nussbaum et al., 1983; Kricher, 1993; Leonard et al., 1993; Stebbins, 2003).

References: (click for full references)

Behler, J. L., and F. W. King. 1979. The Audubon Society Field Guide to North American Reptiles and Amphibians. Alfred A. Knopf, Inc., New York. 743 pp.

Beltz, E. 2005. Frogs. Inside Their Remarkable World. Firefly Books Ltd, Richmond Hill, Ontario, and Buffalo, New York. 175 pp.

Campbell, R. W., M. G. Shepard, B. M. Van Der Raay, and P. T. Gregory. 1982. A bibliography of Pacific Northwest herpetology. British Columbia Provincial Museum Heritage Record (14):i-vi, 1-151.

Case, S. M., P. G. Haneline, and M. F. Smith. 1975. Protein variation in several species of Hyla. Systematic Zoology 24(3):281-295.

Collins, J. T., and T. W. Taggart. 2002. Standard Common and Current Scientific Names for North American Amphibians, Turtles, Reptiles & Crocodilians. Fifth Edition. The Center for North American Herpetology, Lawrence, Kansas.  44 pp.

Cook, F. R. 1984. Introduction to Canadian Amphibians and Reptiles. National Museums of Canada, Ottawa. 200 pp.

Crother, B. I., J. Boundy, J. A. Campbell, K. de Quieroz, D. Frost, D. M. Green, R. Highton, J. B. Iverson, R. W. McDiarmid, P. A. Meylan, T. W. Reeder, M. E. Seidel, J. W. Sites, Jr., S. G. Tilley, and D. B. Wake. 2003. Scientific and standard English names of amphibians and reptiles of North America north of Mexico:  Update. Herpetological Review 34(3):196-203.

Crother, B.I. (chair). Committee on Standard and English and Scientific Names. 2008. Scientific and standard English names of amphibians and reptiles of North America north of Mexico, with comments regarding confidence in our understanding. Society for the Study of Amphibians and  Reptiles Herpetological Circular. No. 37. iii + 86p.

Dornburg, A., and R. E. Weaver. 2007. Geographic distribution. Pseudacris pacifica (Pacific treefrog). USA: Washington. Herpetological Review 38(3):349-350.

Duellman, W. E., and S. S. Sweet. 1999. Distribution patterns of amphibians in the Nearctic Region of North America. Pp. 31-109. In: W. E. Duellman (editor). Patterns of Distribution of Amphibians. A Global Perspective. The Johns Hopkins University Press, Baltimore. 633 pp.

Faivovich, J., C. B. F. Haddad, P. C. A. Garcia, D. R. Frost, J. A. Campbell, and W. C. Wheeler. 2005. Systematic review of the frog family Hylidae, with special reference to Hylinae: Phylogenetic analysis and taxonomic revision. Bulletin of the American Museum of Natural History 294:1-240.

Frost, D. R. (editor). 1985. Amphibian Species of the World. A Taxonomic and Geographical Reference. Allen Press, Inc. and The Association of Systematics Collections. Lawrence, Kansas. 732 pp.

Frost, D. [R.] (compiler). 2000 [2001]. Anura—frogs. Pp. 6-17. In: B. I. Crother (chair), and Committee on Standard English and Scientific Names (editors). Scientific and standard English names of amphibians and reptiles of North America north of Mexico, with comments regarding confidence in our understanding. Society for the Study of Amphibians and Reptiles Herpetological Circular (29):i-iii, 1-82.

Frost, D. [R.] 2007. Amphibian Species of the World 5.1, an Online Reference. American Museum of Natural History, New York. Available on URL:

Frost, D. R., T. Grant, J. Faivovich, R. H. Bain, A. Haas, C. F. B. Haddad, R. O. De Sá, A. Channing, M. Wilkinson, S. C. Donnellan, C. J. Raxworthy, J. A. Campbell, B. L. Blotto, P. Moler, R. C. Drewes, R. A. Nussbaum, J. D. Lynch, D. M. Green, and W. C. Wheeler. 2006. The amphibian tree of life. Bulletin of the American Museum of Natural History 297:1-370 + Fig. 50 foldout.

Frost, D. R., R. W. McDiarmid, and J. R. Mendelson III. 2008. Anura—frogs. Pp. 2-12. In: B. I. Crother (chair), and Committee on Standard English and Scientific Names (editors). Scientific and standard English names of amphibians and reptiles of North America north of Mexico, with comments regarding confidence in our understanding. Sixth Edition. Society for the Study of Amphibians and Reptiles Herpetological Circular (37):1-84.

Gregory, P. T., and R. W. Campbell. 1984. The reptiles of British Columbia. [Second edition.] British Columbia Provincial Museum Handbook (Victoria) (44):i-viii, 1-103.
Hodge, R. P. 1976. Amphibians & Reptiles in Alaska, the Yukon & Northwest Territories. Alaska Northwest Publishing Company, Anchorage. 89 pp.

Howland, J.M. 1996. Herps of Arizona. The Desert Monitor 27(1):12-17.

Jameson, D. L., J. P. Mackey, and R. C. Richards. 1966. The systematics of the Pacific tree frog, Hyla regilla. Proceedings of the California Academy of Sciences, Fourth Series 33(19):551-620.

Kricher, J. C. 1993. A Field Guide to the Ecology of Western Forests. Houghton Mifflin Company, Boston. 554 pp.

Leonard, W. P., H. A. Brown, L. C. Jones, K. R. McAllister, and R. M. Storm. 1993. Amphibians of Washington and Oregon. Seattle Audubon Society, Seattle. 168 pp.

Nussbaum, R. A., E. D. Brodie Jr., and R. M. Storm. 1983. Amphibians and Reptiles of the Pacific Northwest. The University Press of Idaho, Moscow, Idaho. 332 pp.

Powell, R., J. T. Collins, and E. D. Hooper, Jr. 1998. A Key to Amphibians & Reptiles of the Continental United States and Canada. University Press of Kansas, Lawrence. 131 pp.

Recuero, E., Í. Marínez-Solano, G. Parra-Olea, and M. García-París. 2006a. Phylogeography of Pseudacris regilla (Anura: Hylidae) in western North America, with a proposal for a new taxonomic rearrangement. Molecular Phylogenetics and Evolution 39(2):293-304.

Recuero, E., Í. Marínez-Solano, G. Parra-Olea, and M. García-París. 2006b. Corrigendum to “Phylogeography of Pseudacris regilla (Anura: Hylidae) in western North America, with a proposal for a new taxonomic rearrangement.” Molecular Phylogenetics and Evolution 41(2):511.

Ripplinger, J. I., and R. S. Wagner. 2004. Phylogeography of northern populations of the Pacific treefrog, Pseudacris regilla. Northwestern Naturalist 85(3):118-125.

Smith, H. M. 1978. A Guide to Field Identification. Amphibians of North America. Golden Press, New York. 160 pp.

Stebbins, R. C. 1954. Amphibians and Reptiles of Western North America. McGraw-Hill Book Company, Inc., New York.537 pp.

Stebbins, R. C. 1985. A Field Guide to Western Reptiles and Amphibians. Second Edition, Revised. Houghton Mifflin Company, Boston. 336 pp.

Stebbins, R. C. 2003. A Field Guide to Western Reptiles and Amphibians. Third Edition. Houghton Mifflin Company, Boston. 533 pp.

Stebbins, R. C., and N. W. Cohen. 1995. A Natural History of Amphibians. Princeton University Press, Princeton. 316 pp.

Test, F. C. 1898. A contribution to the knowledge of the variations of the tree frog Hyla regilla. Proceedings of the U. S. National Museum 21 1899(1156):477-492, pl. xxxix.

Waters, D. L. 1992. Geographic distribution: Pseudacris regilla (Pacific chorus frog). USA: Alaska: Alexander Archipelago, Revillagigedo Island. Herpetological Review 23(1):24-25.

Waters, D. L., T. J. Hassler, and B. R. Norman. 1998. On the establishment of the Pacific chorus frog, Pseudacris regilla (Amphibia, Anura, Hylidae), at Ketchikan, Alaska. Bulletin of the Chicago Herpetological Society 33(6):124-127.

Werner, J.K., B.A. Maxwell, P. Hendricks, and D.L. Flath. 2004. Amphibians and reptiles of Montana. Mountain Press Publishing Company, Missoula, Montana.

Wright, A. H., and A. A. Wright. 1949. Handbook of Frogs and Toads of the United States and Canada. Third Edition. Cornell University Press, Ithaca and London. 640 pp.

Author: Louis A. Somma, and Robert S. Powell

Revision Date: 8/17/2015

Citation Information:
Louis A. Somma, and Robert S. Powell, 2018, Pseudacris regilla (Baird and Girard, 1852): U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL,, Revision Date: 8/17/2015, Access Date: 1/16/2018

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.

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Citation information: U.S. Geological Survey. [2018]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [1/16/2018].

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