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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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Juvenile, Santa Ana mountains,
Riverside County |
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| Adult, San Diego County, © Stuart Young |
Adult, San Diego County, © Stuart Young |
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Herpetologist Sam Sweet has posted some outstanding descriptions of the biology of Arroyo Toads - their breeding, egg deposition, tadpoles and metamorphs - including comparisons with sympatric Bufo (Anaxyrus) boreas, illustrated with many excellent photographs. These are on public herping forums where you can see them here and here.
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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, Riverside County |
Habitat, Riverside County |
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Habitat, San Diego County |
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Arroyo Toad sign, Riverside County |
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Short Video
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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. |
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Description |
Size |
| Adults are 1 4/5 - 3 2/5 inches from snout to vent ( 4.6 - 8.6 cm). |
| Appearance |
| Plump and stocky with dry, uniformly warty skin. No cranial crests. Oval, widely separated parotoid glands that are pale toward the front. Pupils are horizontal. Greenish, gray, olive, dull brown above. No stripe down the middle of the back. Warts have brown tips on the tubercles. Usually with a light stripe or patch on the head and eyelids. Whitish below, with no spots or mottling. Male and female throats are pale. Young are pale, often with no dark spots, and tubercles on back are yellowish. Moves by quickly hopping, instead of walking. |
| 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. |
| Behavior |
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. Toads are active from the first substantial rains from January to March, through August or September.
For defense, this toad uses parotoid glands and warts which can secrete a poison that deters some predators. Other predators are immune to the poison, and will consume the toads.
Toads do not seem to be territorial, but they tend to be fairly sedentary and faithful to breeding sites.
Life expectancy is generally four years. Females live a bit longer than males. |
| Diet |
| 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. The 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. |
| Reproduction and Young |
Reproduction is aquatic. Fertilization is external. 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.)
Most males become reproductively mature in their second year. Most females are mature in their third year.
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 are when they are ready to breed.
The male amplexes the female and she lays her eggs at the male's calling site. She does not typically carry him to another site.
Eggs are laid in long strings with two strands, containing an average of 4,700 eggs. Egg-laying sites are exposed shallow flowing water without any twigs, roots, or debris to tangle the 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 hatch from the eggs after about 4 - 6 days, but remain with the decaying egg matter for another two weeks.
Tadpoles begin as black in color, turning to a lighter cryptic shade to render them almost invisible in the sandy substrate. Unlike all other California tadpoles, Arroyo Toads sift a substrate of fine sediments for food, making them extremely dependant on this specialized habitat. 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. |
| Range |
Endemic to California and northern Baja California. Ranges west of the desert in coastal areas from the upper Salinas River system in San Luis Obispo county to northwestern Baja California.
"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 |
| Habitat |
Inhabits washes, arroyos, sandy riverbanks, riparian areas with willows, sycamores, oaks, cottonwoods. Extremely specialized habitat needs, including 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.
Sea level to 3,000 ft. (900 m.) |
| Taxonomic Notes |
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 most existing references. |
| 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. |
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Taxonomy |
| Family |
Bufonidae |
True Toads |
| Genus |
Anaxyrus |
North American Toads |
| Species |
californicus |
Arroyo Toad
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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
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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
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Alternate Names |
Formerly Bufo microscaphus microscaphus, Arroyo Toador Arroyo Southwestern Toad.
Bufo californicus
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Related or Similar California Frogs |
Anaxyrus boreas boreas
Anaxyrus boreas halophilus
Anaxyrus woodhousii
Anaxyrus canorus
Anaxyrus exsul
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More Information and References |
Natureserve Explorer
California Dept. of Fish and Game
AmphibiaWeb
SD Natural History Museum
Pasadena Audubon 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.
Wright, Anna. 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.
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The following status listings come from the Special Animals List which is published several times each year by the California Department of Fish and Game.
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Organization
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Status Listing
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| U.S. Endangered Species Act (ESA) |
FE |
Endangered |
| California Endangered Species Act (CESA) |
None |
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| California Department of Fish and Game |
DFG:SSC |
California Species of Special Concern |
| Bureau of Land Management |
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| USDA Forest Service |
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| Natureserve Global Conservation Status Ranks |
G2G3 S2S3 |
Imperiled, Vulnerable |
World Conservation Union - IUCN Red List
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IUCN:EN |
Endangered |
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