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A Guide to the Amphibians
and Reptiles of California


Arroyo Toad - Anaxyrus californicus

(Camp, 1915)

(= Bufo californicus)
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arroyo toad range map
Range in California: Red

Dot-locality range map

Listen to this toad:

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One short call



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Adult male, desert side of San Bernardino Mountains, San Bernardino County
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Adult male, desert side of San Bernardino Mountains, San Bernardino County
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Adult, San Diego County,
© Stuart Young
Adult, San Diego County,
© Stuart Young
Adult, San Diego County,
© Jason Jones
     
Juveniles
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Juvenile, Santa Ana mountains,
Riverside County
Juvenile, Ventura County
© Patrick Briggs
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Recently-metamorphosed juveniles in early July, San Bernardino County
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Recently-metamorphosed juveniles in early July, San Bernardino County This recently-metamorphosed juvenile blends in with the sand background on which it spends its early life.
     
Beeding, Eggs and Tadpoles
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Close-up of egg strings, San Bernardino County  © 2005 Chris Brown, USGS Adults in amplexus, Baja California
© James R. Buskirk
Tadpoles, San Bernardino County
© 2005 Chris Brown, USGS
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Young Tadpoles in May, San Bernardino County © Mark Gary
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Young Tadpoles in May, San Bernardino County © Mark Gary Tadpole, Santa Barbara County,
© Ronn Altig
 
 
Herpetologist Sam Sweet has posted some outstanding descriptions of the biology of Arroyo Toads - their breeding, egg deposition, tadpoles and metamorphs, illustrated with many excellent photographs, and including comparisons with sympatric California Toads. These are on public herping forums where you can see them here and here.
 
Habitat
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Habitat, desert side of San Bernardino Mountains, San Bernardino County Habitat, Mojave River north of Lancaster, Los Angeles County
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Habitat, San Diego County Habitat, Santa Ana Mountains,
Riverside County
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Habitat, San Gabriel Mountains,
Los Angeles County
Habitat, San Diego County Habitat, Ventura County
© Patrick Briggs
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Habitat, Ventura County
© Patrick Briggs
Habitat with tadpoles in May, San Bernardino County © Mark Gary Habitat with recently-metamorphosed juveniles in early July, San Bernardino County © Mark Gary
arroyo toad habitat sign arroyo toad habitat sign  
Los Angeles County sign,
© William Flaxington
Arroyo Toad sign, Riverside County  
     
Short Video
  arroyo toad habitat  
  A male Arroyo Toad calls three times at night from the edge of a creek in San Bernardino County. The video has been edited - the original calls were about a minute apart.  

Description
 
Size
Adults are 1.75 - 3.2 inches from snout to vent ( 4.6 - 8.6 cm). (Stebbins & McGinnis 2012)

Appearance
A plump and stocky toad with dry, uniformly warty skin.
No cranial crests are present.
Paratoid glands are oval, widely separated, and pale in color toward the front.
Pupils are horizontal.
Color and Pattern
Greenish, gray, olive, dull brown above.
Warts set on dark blotches have brown tips on the tubercles.
No stripe is present down the middle of the back.
There is typically a light stripe or patch across the head and eyelids.
Often there is a patch of light coloring on the sacral humps (in the middle of the lower back.)
Whitish  in color below, with no spots or mottling.
The throat is pale on both males and females.
Young
Young are pale, often with no dark spots, and warts have tubercles with yellow tips.
Larvae (Tadpoles)
Tadpoles grow to about 1.5 inches long (3.7 cm) before undergoing metamorphosis.
Color is forming a cryptic pattern enabling a tadpole to blend in with the sandy stream substrate.
Tadpoles begin black in color, then begin to show areas of lighter color on top of the tail white patches on their bottoms. Eventually the body coloring becomes a light cryptic shade of tan or olive or gray with black or brown mottling which renders them almost invisible in the sandy substrate.
Look here to see some great pictures of Arroyo Toad tadpoles.
Comparison with Sympatric California Toads
(From Sweet, 2010, 1 and 2)

Adults


Arroyo toads typically have a light stripe or V across the head and eyelids which is lacking on California Toads.
Mature California Toads typically have a pale dorsolateral stripe (a pale light stripe down the middle of the back) which is lacking on Arroyo Toads.


Juveniles

Juvenile Arroyo Toads show the pale V between the eyes, pale spots on the sacral humps, yellow tubercles, and are unmarked ventrally.
Juvenile Calfornia Toads have no pale V or pale sacral hump spots, rust-colored turbercles, a pale dorsolateral stripe, and are marked with dark spots ventrally.

Juvenile Arroyo toads are typically found fully exposed in direct sunlight on the sandy banks of the natal creek.
Juvenile California toads are typically found dug into wet sand at the edge of the creek, or in shade under vegetation.


Tadpoles

Hatchling California Toad tadpoles and Arroyo Toad tadpoles appear very dark.
As they age, Arroyo Toad tadpoles develop white markings on the top of the tail and white patches on their bottom while California Toad tadpoles remain dark.

Mature California Toad tadpoles appear dark with light mottling.
Mature Arroyo Toad tadpoles appear light with dark mottling.

Arroyo Toad tadpoles tend to remain motionless more than California Toad tadpoles. About a quarter of a small group of Calfornia Toad tadpoles will be active at any moment, while only a few individuals in a small group of Arroyo Toad tadpoles will be moving at any moment.

Metamorphosing Arroyo Toad tadpoles show the pale V between the eyes, pale spots on the sacral humps, and yellowtubercles.
Metamorphosing California Toads are darker with no pale V or sacral hump coloring, and rust-colored tubercles.

Life History and Behavior
Activity
Adults are nocturnally active, remaining underground in the daytime, but occasionally seen moving about in daylight or resting at the edge of breeding pools in the breeding season.
Newly-transformed juveniles are diurnal.
Arroyo Toads are active from the first substantial rains from January to March, through August or September.
Movement
Moves by quickly hopping, instead of walking.
Defense
This toad uses poison secretions from parotoid glands and warts to deter predators.
Some predators are immune to the poison, and will consume toads.
Territoriality
Toads do not seem to be territorial, but they tend to be fairly sedentary and faithful to breeding sites.
Longevity
Life expectancy is generally four years. Females live a bit longer than males.
Voice   (Listen)
The advertisement call of the Arroyo Toad is a fast musical trill, about 10 seconds, rising in pitch, and ending abruptly.
This call is similar to that of Anaxyrus punctatus - Red-spotted Toad, but with a lower pitch. It can be heard at a distance.
Diet and Feeding
Adults eat a wide variety of invertebrates, but mostly consume ants, especially nocturnal, trail-forming tree ants.
Juveniles feed mostly on ants and small flies.
Prey is located by vision then the toad lunges with a large sticky tongue to catch the prey and bring it into the mouth to eat.
Unlike all other California tadpoles, Arroyo Toads sift a substrate of fine sediments for food, making them extremely dependant on their unique and fragile habitat of streams with wet sandy stable shorelines.
Breeding
Breeding 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 migrate to streams 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.

Most males become reproductively mature in their second year, females in their third year.

Mating and egg-laying takes place at the quiet margins of shallow streams from March to July.
Breeding is not triggered by rainfall, but seems to require an increase in air and water temperature to above 11-13 degrees C. (51.8 - 55.4 degrees F.)

Males do not form large calling groups and satellite breeding behavior has not been observed. A single male will take a position at night at a good egg-laying location, typically a flat exposed stream bank with still shallow water, but always with some current flowing through it. There he makes his trilled advertisement call. Females select a male by his sound, then move toward the streamside area when they are ready to breed.  The male amplexes the female grabbing her behind her forelimbs then she lays her eggs at the male's calling site. She does not typically carry him to another site.
Eggs
Egg-laying sites are exposed shallow flowing water without any twigs, roots, or debris to tangle the eggs.
Eggs are laid in long strings with two strands of ova, containing an average of 4,700 eggs.
Eggs are subject to mortality from water level changes, from both declines in water level, and flooding: eggs that are stranded when water level drops dry up and do not hatch; eggs that are swept into cooler deeper water are usually attacked by fungus and do not survive.
Tadpoles and Young
Tadpoles hatch from the eggs after about 4 - 6 days, but they cannot swim for several days, during which time a change in the water level can wash them away or strand them.
Eggs and tadpole hatchlings are protected by toxins and are ignored by predators.
Tadpoles begin black in color, then begin to show areas of lighter color on the tails and body, eventually turning to a light cryptic shade which renders them almost invisible in the sandy substrate.

Larvae reach metamorphosis in 72 - 80 days. Most metamorphosis occurs from late May to early July. Sometimes it occurs as early as late April and as late as early October.

Newly metamorposed toads stay 3 - 5 weeks on the exposed sand and gravel bars where they forage in full sunlight in high heat. They take shelter in damp depressions in the gravel. Eventually they become nocturnal, burrowing into dry sand during daylight, and disperse farther from the stream, typically as the stream dries up.

Habitat
Inhabits washes, arroyos, sandy riverbanks, riparian areas with willows, sycamores, oaks, cottonwoods.

Arroyo Toads have extremely specialized habitat needs, which include exposed sandy streamsides with stable terraces for burrowing with scattered vegetation for shelter, and areas of quiet water or pools free of predatory fishes with sandy or gravel bottoms without silt for breeding.

"Arroyo toads are closely associated with low gradient drainages from near sea level to about 1,400 m elevation [4,600 ft.] (to a maximum of 2,440 m  [8,005 ft.] in Baja California del Norte), with most remaining populations residing in the 300–1,000 m range [984 - 3280 ft.] (USFWS, 1999a)."    (Sweet & Sullivan in Lanoo, 2005).

Geographical Range
Endemic to California and northern Baja California. Ranges west of the desert in coastal areas, from the upper Salinas River system in Monterey county to northwestern Baja California del Norte.

"The arroyo toad has been recorded at six locations on the desert slope (Patton and Myers 1992): the Mojave River, Little Rock Creek, Whitewater River, San Felipe Creek, Vallecito Creek, and Pinto Canyon." CDF&G

1 Ervin et al (2013) presented evidence that "the arroyo toad (Anaxyrus californicus) is not confirmed to occur within the Sonoran Desert portions of Riverside, San Diego, and Imperial counties, California. In the Mojave Desert, the species is currently known from two areas, Littlerock Creek, Los Angeles County and the Mojave River Watershed, San Bernardino County. The validity of the Banner Canyon record reported here remains in question."

The Whitewater River, San Felipe Creek, Vallecito Creek, and Pinto Canyon records are shown to be based on errors.

Full Species Range Map
Elevational Range
Found at elevations in California from near sea level to above 3,900 ft. (1190 m.) (High elevation record from USGS surveys at Cuyamaca Rancho State Park 2003, 2005.)

Notes on Taxonomy
In 1998 Bufo microscaphus was split into two species, Bufo californicus, and B. microscaphus.
Some sources still list Bufo californicus as a subspecies of Bufo microscaphus, Bufo microscaphus californicus.

Formerly included in the genus Bufo. In 2006, Frost et al replaced the long-standing genus Bufo in North America with Anaxyrus, restricting Bufo to the eastern hemisphere. Bufo is still used in many existing references.


Alternate and Previous Names (Synonyms)

Bufo californicus
- Arroyo Toad (Stebbins 2003, Stebbins & McGinnis 2012)
Bufo microscaphus californicus - Arroyo Toad (Stebbins 1954, 1966, 1985)
Bufo californicus - Southern California Toad (Arroyo Toad) (Wright and Wright 1949)
Bufo cognatus californicus - Arroyo Toad (Storer 1925)
Bufo cognatus (Say 1823)

Conservation Issues  (Conservation Status)
This toad is estimated to be absent from 65 to 75 per cent of its historic range. It is possible that this number is even higher because the historic estimate may be based only on remaining populations, when toads actually also inhabited streams in areas that were urbanized or altered before the toadswere known. Remaining population densities of this toad, once historically high, are now relatively low, especially at montane and foothill locations. They are a bit higher at coastal stream locations. These remaining populations are extremely vulnerable due to isolation from other populations, and to specialized habitat needs which include fragile sandy streamside habitat and streams that have not been heavily silted. The loss or degradation of this specialized habitat is a major problem. Causes for habitat loss include the results of mining, urban development, grazing cattle, and other sources of stream trampling such as excessive human recreational use, including campgrounds and vehicles driving across streams. Streamside trampling crushes and destroys all the juveniles, since they feed by remaining on sandy stream-banks. Exotic aquatic predators such as bullfrogs, fish and crayfish, also reduce toad populations.

Taxonomy
Family Bufonidae True Toads Gray, 1825
Genus Anaxyrus North American Toads Tschudi, 1845
Species californicus Arroyo Toad

(Camp, 1915)
Original Description
Bufo californicus Camp, 1915 - Univ. California Publ. Zool., Vol. 12, p. 331

from Original Description Citations for the Reptiles and Amphibians of North America © Ellin Beltz

Meaning of the Scientific Name
Bufo - toad
Anaxyrus -
Greek - A king or chief
Californicus refers to belonging to the state of California - the type locality is Ventura County, CA, 1912

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

Related or Similar California Frogs
Anaxyrus boreas boreas
Anaxyrus boreas halophilus

Anaxyrus woodhousii
Anaxyrus canorus
Anaxyrus exsul

More Information and References

California Department of Fish and Wildlife

AmphibiaWeb

SD Natural History Museum

Pasadena Audubon

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.

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.

1 Edward L. Ervin, Kent R. Beaman, and Robert N. Fisher. Correction of Locality Records for the Endangered Arroyo Toad (Anaxyrus californicus) from the Desert Region of Southern California.
Bull. Southern California Acad. Sci.112(3), 2013, pp. 197–205 © Southern California Academy of Sciences, 2013  DOI
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.


Special Animals List Notes:

1) Formerly Bufo microscaphus californicus, now considered a full species.

2) At the time of listing, arroyo toad was known as Bufo microscaphus californicus, a subspecies of southwestern toad. In 2001 it was determined to be its own species, Bufo californicus. Since then, many species in the genus Bufo were changed to the genus Anaxyrus, and now arroyo toad is known as Anaxyrus californicus (Frost et al. 2006).

Organization
Status Listing
NatureServe Global Ranking G2G3 Imperiled - Vulnerable
NatureServe State Ranking S2S3 Imperiled - Vulnerable
U.S. Endangered Species Act (ESA) FE - 1/17/95 Endangered
California Endangered Species Act (CESA) None
California Department of Fish and Wildlife SSC Species of Special Concern
Bureau of Land Management None
USDA Forest Service None
IUCN EN Endangered
 

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