The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

Pseudacris hypochondriaca
Pseudacris hypochondriaca
(Baja California Treefrog)
Native Transplant

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Pseudacris hypochondriaca (Hallowell, 1854)

Common name: Baja California Treefrog

Synonyms and Other Names: San Lucan chorus frog,

Taxonomy: available through www.itis.govITIS logo

Identification: Pseudacris hypochondriaca 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 (Stebbins, 1972, 2003; Lamar, 1997; Brennan and Holycross, 2006).  Unlike Pseudacris cadaverina, the California chorus frog, a black or dark brown eyestripe or mask is more often present, green is the more common dorsal color, and the toe pads are not as large and conspicuous (Stebbins, 2003).  Unlike Hyla wrightorum, the Arizona Treefrog, the eyestripe rarely extends beyond the shoulder (Powell et al., 1998; Grismer, 2002; Stebbins, 2003; Brennan and Holycross, 2006).  See the species account titled “Hyla wrightorum Taylor, 1938” on this website. Distinct morphological criteria for distinguishing P. hypochondriaca from its sister species the Northern Pacific Treefrog, Pseudacris regilla, have not yet been established. See the species account titled “Pseudacris regilla (Baird and Girard, 1852)” on this website. The Baja California Treefrog’s call is the stereotypical, loud, two-part “kreck-ek” or “ribbit” most commonly used on Hollywood movie soundtracks regardless of the locality depicted in the movie (Davidson, 1995, 1996; Bogert, 1998; Stebbins, 2003; Beltz, 2005). Recordings of their calls are even used for plastic toy and novelty frogs. It is shorter, lower-pitched, and less musical than the call made by P. cadaverina (Stebbins, 2003). Recordings of the calls of P. hypochondriaca are widely available on CDs, but under the name P. regilla (Wilson, 1993; Elliott, 1994; Davidson, 1995, 1996; Bogert, 1998). The tadpoles of P. hypochondriaca are light greenish gray or olive brown, have high tail fins, and the internal viscera can be seen ventrally (Stebbins, 1972, 2003).

Baja California Treefrogs have been illustrated by a variety of authorities under the name Pacific chorus frog (Test, 1989; Wright and Wright, 1949; Stebbins, 1972, 1985, 2003; Smith, 1978; Behler and King, 1979; Kricher, 1993; Stebbins and Cohen, 1995; Lamar, 1997; Grismer, 2002; Beltz, 2005; Brennan and Holycross, 2006). Halliday (2002) illustrates skeletal deformities found in natural populations.

Size: SVL is 19-50 mm

Native Range: Pseudacris hypochondriaca is indigenous to Pacific and western regions of North America, from Nevada, most of southern California (except for some desert regions, but including some offshore islands), northwestern Arizona (Mohave County along the Colorado River), and Baja California, Mexico (Test, 1898; Stebbins, 1954, 1972, 2003; Jameson et al., 1966; Glaser, 1970; Smith and Smith, 1973, 1976, 1993; Flores-Villela, 1993; Lamar, 1997; Duellman and Sweet, 1999; Grismer, 2002; Brennan and Holycross, 2006; Recuero et al., 2006a; Luja et al., 2007).  

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Nonindigenous Occurrences:

Table 1. States with nonindigenous occurrences, the earliest and latest observations in each state, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Pseudacris hypochondriaca are found here.

StateFirst ObservedLast ObservedTotal HUCs with observations†HUCs with observations†
CA198519851Antelope-Fremont Valleys
CO198219942Big Thompson; Colorado Headwaters-Plateau

Table last updated 4/21/2024

† Populations may not be currently present.

Ecology: Pseudacris hypochondriaca frequents a variety of habitats and elevations, from sea level to mountains, from grasslands and chaparral, to forests, farmlands, and desert oases (Grismer and McGuire, 1993; Kricher, 1993; Grismer, 2002; Stebbins, 2003). This adaptable little hylid is chiefly a terrestrial, nonclimber, preferring to remain among low plants near or along water (Grismer, 2002; Stebbins, 2003; Brennan and Holycross, 2006). Individuals of varying colors will preferentially select microhabitat substrates that most closely match their individual color (Morey, 1990; Stebbins and Cohen, 1995).  They breed and lay their eggs in a variety of waters including marshes, ponds, lakes, reservoirs, slow streams, and roadside ditches (Kricher, 1993; Grismer, 2002; Stebbins, 2003; Luja et al., 2007).

Means of Introduction: The Baja California chorus frogs brought into plant shops in Larimer and Mesa Counties, Colorado, were clearly transported on plants.

It is not entirely known how a nonindigenous species of the P. regilla complex was introduced to Arizona although plant nurseries are involved in a some cases (Brennan and Holycross, 2006). Indigenous populations of P. hypochondriaca exist in the northwestern region of the state (Stebbins, 1985, 2003; Brennan and Holycross, 2006; Recuero et al., 2006a).

The means of introduction for P. hypochondriaca population in Kern County is unknown, and it is possible it may be an indigenous population (Stebbins, 1985; Recuero at al., 2006). Perhaps it is a relict population.

Status: The P. hypochondriaca from Larimer and Mesa Counties, Colorado, were collected and not established (Livo et al., 1998).

Nonindigenous chorus frogs are established in Arizona (Brennan and Holycross, 2006), but it is not clear which species is involved.

Suspected nonindigenous P. hypochondriaca are established in Kern County, California (Stebbins, 2003). They seem confined to a desert oasis.

Impact of Introduction: There was no impact caused by nonindigenous P. hypochondriaca in Colorado as they were all collected from plant shops (Livo et al., 1998).

The impact of suspected nonindigenous Pseudacris in Arizona and California will remain unclear as long as their exact species identity or status as nonindigenous or indigenous populations remains uncertain.

Remarks: The taxonomy of P. hypochondriaca and 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; Faivovich et al., 2005; Frost et al., 2006, 2008; Recuero et al., 2006a, b). Recuero et al. (2006a, b) revised the Pacific chorus frog complex by splitting it into three species: P. hypochondriaca, P. sierra, and P. regilla. See the species accounts titled “Pseudacris sierra (Jameson, Mackey, and Richmond, 1966)” and “Pseudacris regilla (Baird and Girard, 1852)” on this website. Further research may reveal that P. hypochondriaca consists of two or more species (Recuero et al., 2006a). Vernacular names used in Mexico are provided by Liner (1994).  The natural history and biology of P. hypochondriaca and its sister species P. sierra are summarized by Wright and Wright (1949), Stebbins and Cohen (1995), Grismer (2002), and Stebbins (2003).  Scientific and standard English names follow Crother (2008).

 Populations in central Baja California, Mexico, are threatened by predation from nonindigenous bullfrogs (Lithobates catesbeianus), nonindigenous fishes, and anthropogenic habitat degradation (Grismer and McGuire, 1993).

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.

Bogert, C. M. 1998. Sounds of North American Frogs. The Biological Significance of Voice in Frogs. Smithsonian Folkways Recordings, Washington, D.C. Audio CD Recording.

Brennan, T. C., and A. T. Holycross. 2006. Amphibians and Reptiles in Arizona. Arizona Game and Fish Department, Phoenix. 150 pp.

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.

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.

Davidson, C. 1995. Frog and Toad Calls of the Pacific Coast. Vanishing Voices. Library of Natural Sounds, Cornell Laboratory of Ornithology, Ithaca. Audio CD Recording.

Davidson, C. 1996. Frog and Toad Calls of the Rocky Mountains. Vanishing Voices. Library of Natural Sounds, Cornell Laboratory of Ornithology, Ithaca. Audio CD Recording.

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.

Elliott, L. 1994. A Guide to Night Sounds. NatureSound Studio, NorthWood Press, Inc., Minocqua, Wisconsin. Audio CD Recording.

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.

Flores-Villela, O. 1993. Herpetofauna Mexicana. Carnegie Museum of Natural History Special Publication (17):i-iv, 1-73.

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: http://research.amnh.org/herpetology/amphibia/index.php.

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.

Glaser, H. S. R. 1970. The Distribution of Amphibians and Reptiles in Riverside County, California. Riverside Museum Press, Riverside. 40 pp

Grismer, L. L. 2002. Amphibians and Reptiles of Baja California. University of California Press, Berkeley and Los Angeles. 391 pp.

Grismer, L. L., and J. A. McGuire. 1993. The oases of central Baja California, México. Part I. A preliminary account of the relict mesophilic herpetofauna and the status of the oases. Bulletin of the Southern California Academy of Sciences 92(1):2024.

Halliday, T. R. 2002. Declining amphibian populations. Pp. 30-33. In: T. [R.] Halliday and K. Adler (editors). Firefly Encyclopedia of Reptiles and Amphibians. [U. S. Edition.] Firefly Books (U. S.) Inc., Buffalo. 240 pp.

Howland, J. M. 1996. Herps of Arizona. The Desert Monitor (Phoenix) 27(1):12-17.
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Livo, L. J., G. A. Hammerson, and H. M. Smith. 1998. Summary of amphibians and reptiles introduced into Colorado. Northwestern Naturalist 79(1):1-11.

Luja, V. H., Ma. C. Blázquez, and R. Rodríguez-Estrella. 2007. Pseudacris hypochondriaca (San Lucan chorus frog). Reproduction. Herpetological Review 38(4):442.

Morey, S. R. 1990. Microhabitat selection and predation in the Pacific treefrog, Pseudacris regilla. Journal of Herpetology 24(3):292-296.

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.

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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.

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Author: Somma, L.A.

Revision Date: 5/16/2018

Citation Information:
Somma, L.A., 2024, Pseudacris hypochondriaca (Hallowell, 1854): U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?SpeciesID=2781, Revision Date: 5/16/2018, Access Date: 4/21/2024

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. [2024]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [4/21/2024].

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