CaliforniaHerps.com

A Guide to the Amphibians
and Reptiles of California


Baja California Treefrog -
Pseudacris hypochondriaca hypochondriaca

(Hallowell, 1854)

(See Alternate Names)
Click on a picture for a larger view



California Treefrogs Range Map
Approximate Range in
California
: Red

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to the other species


Listen to this frog:



Solo Calls




observation link





Baja California Treefrog Baja California Treefrog Baja California Treefrog Baja California Treefrog
Adult, San Gabriel Mountains, Los Angeles County Adult, San Diego County
Adult, San Diego County
Baja California Treefrog Baja California Treefrog Baja California Treefrog Baja California Treefrog
Adult male, San Diego County Adult, Tejon Pass, Los Angeles County Nearly patternless adult, Orange County © Craig Hoover
Baja California Treefrog Baja California Treefrog Baja California Treefrog Baja California Treefrog
Adult female, Tehachapi Mountains, Kern County Adults, Orange County © Jeff Ahrens Adult, Orange County © Jeff Ahrens
Baja California Treefrog Baja California Treefrog Baja California Treefrog Baja California Treefrog
Adult, Orange County © Jeff Ahrens Adult, Orange County © Jeff Ahrens Adult, Riverside County © Jeff Ahrens
Baja California Treefrog Baja California Treefrog Sierran Treefrog  
Adult, Kern County Using the enlarged pads on their toes, Baja California Treefrogs are excellent climbers. They can even climb up glass.
Adult Sierran treefrog, showing the yellow "flash color" markings on the inner thighs which are also evident on this species.  When the frog fears an attack from a predator, it jumps away, stretching the legs out and exposing the bright color. The predator automatically focuses on the bright color when it pursues the frog, but the color suddenly disappears when the frog lands and folds up its legs. This can confuse the predator long enough to allow the frog to escape.  
       
Breeding Adults
Baja California Treefrog Baja California Treefrog Baja California Treefrog  
Calling adult male, Orange County
© Jason Jones
Calling adult male, Los Angeles County Adults in amplexus, Riverside County.
© Mike Pecora
 
       
Identification
Baja California Treefrog Baja California Treefrog Baja California Treefrog  
Suction-cup-like, enlarged toe pads, seen from underneath. Comparison of a California Treefrog (bottom) and a Baja California Treefrog (top) coexisting in the same creek in the San Gabriel Mountains, Los Angeles County. Note the dark mask through the eye of the Baja California Treefrog which is not present on the California Treefrog. Comparison of the undersides of a California Treefrog (top) and a Baja California Treefrog (bottom) coexisting in the same creek in the San Gabriel Mountains, Los Angeles County  

Click here to see pictures illustrating Baja California Treefrog Eggs and Tadpoles



Habitat
Baja California Treefrog Habitat Baja California Treefrog Habitat Baja California Treefrog Habitat Baja California Treefrog Habitat
Habitat, pond in San Diego County coastal chaparral Habitat, riparian desert canyon,
Riverside County
Desert riparian canyon habitat,
San Bernardino County
Habitat, 340 ft. Kern County
Baja California Treefrog Habitat Baja California Treefrog Habitat Baja California Treefrog Habitat Baja California Treefrog Habitat
Habitat, small creek, San Gabriel Mountains, Los Angeles County Habitat, creek, coastal
San Diego County
Habitat,2,500 ft. Tehachapi Mountains, Kern County
Habitat, 2,500 ft. Kern County
Baja California Treefrog Habitat Baja California Treefrog Habitat    
Habitat (riparian) 800 ft.,
San Diego County
Egg-laying habitat, San Diego County 
© Jeff Ahrens
   
       
Short Videos
  Baja California Treefrog Baja California Treefrog  
  A male Baja California Treefrog calls at night as part of a chorus of frogs in Kern County. He starts with the two-parted call, then speeds up a bit slurring the two parts together into what is almost a one-part call which he then alternates with the two-parted call.  A Baja California Treefrog in a small mountain stream.  
     
Description
 
Size
Adults are .75 - 2 inches long from snout to vent (1.9 - 5.1 cm). (Stebbins, 2003)

Appearance
A small frog 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.
Color and Pattern
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.
Male/Female Differences
The male's throat is darkened and wrinkled.
Young
Similar to adults.
Larvae (Tadpoles)
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.

Comparison with sympatric California Treefrogs - Pseudacris cadaverina
Adults

Baja California Treefrogs have a dark stripe through each eye.
California Treefrogs do not have a dark stripe through each eye.

Baja California Treefrogs are found in a variety of colors including greens, greys and browns.
California Treefrogs are mostly pale with some dark markings.


Tadpoles

Baja California Treefrog tadpoles have eyes that when seen from above are on the edge of the outline of the head.
California Treefrog tadpoles have eyes that, when viewed from above, are set barely within the outline of the head.

California Treefrog tadpoles have a flatter body than those of Baja California Treefrogs, and a more acute snout.
(Stebbins & McGinnis, 2012)

Life History and Behavior
Activity
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.

The name "treefrog" is not entirely accurate. 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.

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.
Defense
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.
Territoriality
Males are territorial during the breeding season, producing a slow trilled encounter call to warn other males.
Longevity
Not known.
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 very loud 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 the beginning of the fall 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 any of these species were used as movie sound effects.)
Diet and Feeding
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.
Breeding
Reproduction is aquatic.
Fertilization is external, with the male grasping the back of the female and releasing sperm as the female lays her eggs.

The reproductive cycle is similar to that of most North American Frogs and Toads. Mature adults come into breeding condition and move to ponds or ditches where the males call to advertise their fitness to competing males and to females. Males and females pair up in amplexus in the water where the female lays her eggs as the male fertilizes them externally. The adults leave the water and the eggs hatch into tadpoles which feed in the water and eventually grow four legs, lose their tails and emerge onto land where they disperse into the surrounding territory.
Breeding and egg-laying occurs between November until July, depending on the location.

Adults probably become reproductively mature in their first year. Mature adults come into breeding condition and move to ponds or ditches where the males call to advertise their fitness to competing males and to females. 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.

Males and females pair up in amplexus in the water where the female lays her eggs as the male fertilizes them externally. The adults leave the water and the eggs hatch into tadpoles which feed in the water and eventually grow four legs, lose their tails and emerge onto land where they disperse into the surrounding territory.

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.
Eggs
Females lay on average between 400 - 750 eggs in small, loose, irregular clusters of 10 - 80 eggs each.
(Rorabaugh & Lannoo, Lannoo, 2005)
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 and Young
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.

Geographical 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 throughout southern California, south of Santa Barbara County and Bakersfield and on the offshore islands, excluding most of the southeast deserts. It ranges farther east into Nevada, and south into Baja California. Also present on Santa Catalina, Santa Cruz, and Santa Rosa Islands.

There are a number of isolated desert locations, including Afton Canyon, Zzyx Springs, Pushawalla Palms, Harper's Well, Little Lake, Trona, Tecopa, Saratoga Springs, the Panamint Mountains, and scattered locations along the Mojave River including Barstow, Oro Grande, and NE of Yermo. Populations at California City and Soda Springs (probably Zzyx) are probably introduced (Stebbins, 2003). Also shown as present along the Colorado River at Lake Havasu, but I find no records yet. I have heard them calling at a pond near Fort Mohave Arizona, just across the river.

Introduced populations in Arizona at plant nurseries near Phoenix and in cattle ponds in the Virgin Mountains (Rorabaugh and Lannoo - Amphibiaweb) might be this species since it is closest to those areas, but they could also have been transported from other locations such as the P. regilla transports in Christmas trees.


The northern contact zone with Pseudacris sierra is unlear. It ranges at least as far north as Bakersfield, and into the Owens Valley, but how far north it ranges in the southern San Joaquin Valley, and whether it occurs in the southern Sierra Nevada mountains, including the Kern Plateau, and the northern Owens Valley, is not clear.

Specific named localities are:

San Diego County, Pala junction on Hwy. 76
Los Angeles County, Santa Monica Mountains
Santa Barbara County, Buellton
Inyo County, Surprise Canyon
Inyo County, Little Lake
Inyo County Indian Joe Canyon
Kern County, Bakersfield
Nye County Nevada, Beatty

  Full Species Range Map
Elevational Range
The former species Pseudacris regilla ranged from sea level to (11,600 ft) in the Sierra Nevada Mountains (3,536 m.) (Rorabaugh and Lannoo - Amphibiaweb).

Notes on Taxonomy
One species (Pseudacris regilla) becomes three species:

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. I am using this taxonomy on this website because it has been adopted by reputable Herpetological associations, but it is not universally accepted, and, in fact, some herpetologist believe that it is not accurate and that there are no obvious differences between the three species of frogs.


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 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.


In a paper published April 2016 * William E. Duellman, Angela B. Marion & S. Blair Hedges present a new phylogenetic tree of hylid frogs (Family Hylidae Rafinesque, 1815) that consists of three families, nine subfamilies, and six resurrected generic names and five new generic names. The family Hylidae contains 7 subfamiles, based on molecular information, not necessarily morphologic characters. Using this tree, the four hylid species found in California become part of the subfamily Acridinae (Acridinae Mivart, 1869) which contains two genera, Pseudacris, and Hyliola (Hyliola Mocquard, 1899.) Our treefrogs (formerly placed in the genus Pseudacris) are placed in the genus Hyliola:

Hyliola cadaverina
(Cope),
Hyliola hypochondriaca (Hallowell),
Hyliola regilla (Baird and Girard) &
Hyliola sierra (Jameson, Mackey, and Richmond.)

* William E. Duellman, Angela B. Marion & S. Blair Hedges. Phylogenetics, classification, and biogeography of the treefrogs (Amphibia: Anura: Arboranae)
Zootaxa 4104 (1): 001–109 http://www.mapress.com/j/zt/ Copyright © 2016 Magnolia Press.
 
Alternate and Previous Names (Synonyms)

The Generic name of this species was changed from Hyla (Treefrogs) to Pseudacris (Chorus Frogs). This creates confusion when some continue to use Treefrog (as I do here, along with the SSAR and the CNAH) because it has been used for many years, and others use Chorus Frog, which is more accurate.


Pseudacris regilla - Pacific Chorus Frog (Pacific Treefrog) (Stebbins & McGinnis 2012)
Hyla regilla - Pacific Treefrog (Stebbins 1966, 1985)
Hyla regilla - Pacific Tree-Frog (Stebbins 1954)
Hyla regilla - Pacific Tree Frog (Pacific Tree Toad, Pacific Hyla, Wood Frog, Pacific Coast Tree Toad) (Wright & Wright 1949)
Hyla regilla - Pacific Tree-toad (Storer 1925)
Hyla curta (Van Denburgh 1905)
Hyla scapularis (Hallowell 1854)
Hyla nebulosa (Hallowell 1854)
Hyla regilla (Baird & Girard 1852)

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 hypochondriaca Baja California Treefrog

(Hallowell, 1854)
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

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

The species name does not mean that this species is a hypochondriac - it refers to the hypochondrium, though I'm not sure why.

hypochondriac - Greek - pertaining to the hypochondrium, the upper lateral region of the abdomen, marked by the lower ribs.

Alternate Names
The Generic name of this species was changed from Hyla (Treefrogs) to Pseudacris (Chorus Frogs). This creates confusion when some continue to use Treefrog (as I do here, along with the SSAR and the CNAH) because it has been used for many years, and others use Chorus Frog, which is more accurate.


Pseudacris hypochondriaca - Baja California Chorus Frog

Pseudacris regilla
- Pacific Chorus Frog

Pseudacris regilla - Pacific Treefrog

Hyla regilla - Pacific Treefrog

Related or Similar California Frogs
Pseudacris regilla - Northern Pacific Treefrog

Pseudacris sierra - Sierran Treefrog

Pseudacris cadaverina - California 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.

Storer, Tracy I. A Synopsis of the Amphibia of California. University of California Press Berkeley, California 1925.

Wright, Albert Hazen and Anna Wright. 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 are copied from the 2017 Special Animals List and the 2017 Endangered and Threatened Animals List which are published by the California Department of Fish and Wildlife.

If no status is listed here, the animal is not included on either CDFW list. This most likely indicates that there are no serious conservation concerns for the animal. To find out more about an animal's status, you can go to the NatureServe and IUCN websites to check their rankings.

Check here to see the most current complete lists.


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
NatureServe Global Ranking
NatureServe State Ranking
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
IUCN
 

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