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).  

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Nonindigenous Occurrences: A single, nonindigenous P. hypochondriaca was found in the early 1980s in a plant shop in Estes Park, Larimer County, Colorado (A. Livo in L. Livo et al., 1998).  Another P. hypochondriaca was collected in a plant nursery in Palisade, Mesa County, Colorado, soon after a shipment of plants arrived from California (Horstman in Livo et al., 1998). (It is possible that these Colorado specimens may actually represent P. sierra, the Sierran chorus frog.)

Howland (1996) lists “P. regilla” as being nonindigenous in Arizona without providing specific locality data. Moreover, Brennan and Holycross (2006) list “P. regilla” populations in Maricopa and Pima Counties, and extreme northwestern Mohave County as nonindigenous. As these publications came out before P. hypochondriaca was split from P. regilla by Recuero et al. (2006a), it is not clear what species of chorus frog is involved.

Stebbins (1985, 2003) suspects that Baja California chorus frogs in California City, Kern County, California, are introduced.  

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). It is interesting to note that Howland (1996) seemed unaware that 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).

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). 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)

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Author: Louis A. Somma

Revision Date: 10/26/2009

Citation Information:
Louis A. Somma. 2017. Pseudacris hypochondriaca. USGS Nonindigenous Aquatic Species Database, Gainesville, FL. Revision Date: 10/26/2009

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Citation information: U.S. Geological Survey. [2017]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [3/30/2017].

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