A Guide to the Amphibians
and Reptiles of California

Sonoran Desert Toad - Incilius alvarius

(Girard, 1859)

(= Bufo alvarius)

Click on a picture for a larger view

Description • Taxonomy • Species Description • Scientific Name • Alt. Names • Similar Herps • References • Conservation Status

Red: Historical Range in California
(Now apparently not found anywhere in California)

Click on the map for a topographical view

Map with California County Names

Listen to this toad:

One short call

More Sounds of
Sonoran Desert Toad

Formerly present, possibly extirpated in California.

All toads shown here were found outside of California.

Adult, Yuma County, Arizona

Adult, Pima County, Arizona

Adult, in breeding pool,
Pima County, Arizona

Adult, Pima County, Arizona

Adult, Maricopa County, Arizona

Juvenile, Pima County, Arizona

Adult, Graham County, Arizona.

Tadpole, Graham County, Arizona
© Albert Most

Former California Habitat / Current Habitat in Arizona

Former habitat - Imperial valley agricultural drain, Imperial County

Sonoran Desert Toads were once recorded from this area between Winterhaven and the Laguna Dam in Imperial County which is now all farmland.

The toad from Yuma County, Arizona, shown above on the top left, was found one night in August on a road between two plowed agricultural fields next to this agricultural drain northeast of Yuma Arizona, about 20 miles east of California. The Sonoran Desert Toad utilized similar developed habitat in California along with undisturbed desert habitat before its disappearance in the state (see the Imperial County photos to the left.) This begs the question, why does this toad still persist in similar agricultural habitat nearby in Arizona and not in California?

Breeding habitat, temporary rain pool, Maricopa County, Arizona

Breeding pool in a flooded wash, Pima County, Arizona. The night before this picture was taken, Sonoran Desert toads sat in the water and on the ground nearby.

Short Video

Sonoran Desert Toads in a rain pool at night in Arizona, including an interaction between two toads where one makes a release call. Lowland Burrowing Treefrogs and Couch's Spadefoots are calling loudly in the background, which might be why these weak-voiced toads were not calling, only waiting around on the banks and in the water for females to come.

Several Sonoran Desert Toads out at night in Arizona, hopping and running quickly across desert roads.

Description

Size

Adults are 4 - 7 1/2 inches from snout to vent (10.1 - 19 cm). (Stebbins, 2003)
The largest toad in California before its presumed extirpation.

Appearance

A large toad with relatively smooth skin, prominent cranial crests, and long parotoid glands behind the eyes.
There is a large white wart near the corner of the mouth and large warts on the hind legs.

Color and Pattern

Olive, dark brown, or dark gray.
The throat is pale on males and females.

Young

Young have light warts set in dark spots.

Larvae (Tadpoles)

Tadpoles are gray to golden brown in color.

Life History and Behavior (based on toads studied outside of California)

Activity

Primarily nocturnal. Active on rainy nights, most often from May to July during summer rains.
Often seen on desert roads in Arizona during the summer monsoons where they frequently suffer from road mortality.
During daylight and hot periods, they will take refuge in rodent burrows amd rocky outcrops. How this toads aestivates or survives over long periods of heat and cold is not known, but one radio-tracked toad remained in the same hiding burrow from late September to mid June, where it may have been in a state of torpor.

Movement

Capable of moving very quickly with huge leaps, and by running across the ground on all four legs.

Defense

As a defense, Sonoran Desert Toads use their large parotoid glands and other warty glands to excrete poisons that may cause paralysis and even death if ingested by dogs and other small animals. Toads assume a butting pose, aiming the parotoid glands at an adversary. They also inflate to increase their body size.

Skin secretions have hallucinogenic properties.
(This is the toad involved in reports of toad licking or the smoking of dried parotoid gland secretions. Some states have passed laws against toad licking or smoking, and classify the secretions of these toads as a controlled substance.)

Longevity

Longevity in the wild is estimated to be at least 4-5 years.

Voice (Listen)

A weak, low-pitched whistling screech, 1/2 - 1 second in duration that cannot be heard as far away as many frogs and toads.
The vocal sac is only vestigial or absent.
Calls at night in small groups, after summer rains.

Diet and Feeding

Like most toads, Sonoran Desert Toads eat anything that it can overtake and capture, mainly a variety of invertebrates, but lizards, mice, and toads have also been observed in its stomach contents. Sometimes this toad can be seen sitting at night under a street light, eating passing flying insects.

Tadpoles are presumed to eat algae and detritus.

Reproduction

Reproduction is aquatic.
Fertilization is external, with the male grasping the back of the female and releasing sperm as the female lays her eggs.
Amplexus is axillary - the male grabs the female around her shoulders or arpits.

The reproductive cycle is similar to that of most North American Frogs and Toads. Mature adults come into breeding condition and migrate to ditches and rain pools 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 locations include seasonal and permanent pools, stock tanks, and irrigation ditches.
Adults breed late spring through early fall, May to September, with the onset of the summer rains.
Breeding often occurs on one night 1 to 3 days after a heavy rain, but if the rain is so heavy that there is substantial flooding, they will wait 2 or 3 days until the water level subsides. ¹
Adults travel up to several hundred meters to water.

Males sometimes give an advertisement call, either by themselves or in a small chorus, but they also travel around and search for females, or sit without calling waiting for females to come close enough to grab them.

Eggs

An average of 7,500 - 8.000 eggs are laid in still or slow-moving water, in long, single, jelly-coated strings or tubes. ¹

Tadpoles and Young

Eggs hatch into tadpoles which are gray to golden brown.
Metamorphosis takes place quickly, usually in less than a month.
Tadpoles grow up to 2.24 inches in length (57 mm).

Hybrids

Presumed hybrids with Woodhouse's Toad have been found in central Arizona. (Stebbins, 2003)

Habitat

Outside of California, this toad inhabits a variety of habitats including grasslands, arid desert lowlands, mountain canyons with oaks and sycamores, and pinyon-oak-juniper mountain forests. Found near washes, river bottoms, springs, reservoirs, canals, irrigation ditches, stock ponds, streams, temporary pools, and sometimes away from water sources.

Geographical Range

The last verified record from California was in 1955, from 7 km north of Winterhaven, but there have been reports of records from near the Arizona side of the Colorado River: near the Cibola National Wildlife Refuge; on the Parker Strip in La Paz County, Arizona; above the confluence of the Gila and Colorado Rivers in yuma County, Arizona; and along the Bill Williams River, Mohave County, Arizona.
(Thomson, Wright, & Shaffer, 2016)

Formerly found in extreme southeast California along the lower Colorado River and in irrigated lowlands of the southern Imperial Valley. It is not known whether toads naturally occured in the Imperial Valley or if they expanded their range there after the development of agricultural irrigation. (Stebbins, 1951 - Thomson, Wright, & Shaffer, 2016)

Outside of California, the species is found in southern Arizona, extreme southwest New Mexico, and in Sonora and northwest Sinaloa, Mexico, and extreme northern Baja California.

Elevational Range

From sea level to 5,784 ft. (1,763 m.) (Stebbins, 2003)

Notes on Taxonomy

The name Colorado River Toad was formerly used for this toad.

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

Changed from Bufo to Ollotis until Frost et al in 2009 showed that Ollotis should be changed to Incilius, Cope 1863.

Darrel R. Frost, Joseph R. Mendelson III, and Jennifer Pramuk Copeia 2009(2): 418

Alternate and Previous Names (Synonyms)

Ollotis alvaria
Bufo alvarius - Sonoran Desert Toad (Colorado River Toad) (Stebbins 1985, 2003, 2012)
Bufo alvarius - Colorado River Toad (Storer 1925, Stebbins 1954, 1966)
Bufo alvarius - Colorado River Toad - Girard's Toad; Colorado Toad (Grinnell and Camp 1917)
Bufo alvarius (Girard 1859)

Conservation Issues (Conservation Status)

In their survey of 1994, Jennings and Hayes noted that this toad is apparently extirpated from most or all of its sites in California. This is likely due to loss of habitat and to pesticide use brought about by modern agricultural methods. According to a California Department of Fish and Game report, no toads have been collected or observed in California since 1955. This toad has also declined in New Mexico, but is abundant in many parts of Arizona.

Taxonomy
Family	Bufonidae	True Toads	Gray, 1825
Genus	Incilius	Central American Toads	Cope, 1863
Species	alvaria	Sonoran Desert Toad	(Girard, 1859)
Original Description
Bufo alvarius Girard, 1859 - in Baird, Report U.S. Mex. Bound. Surv., Vol. 2, Rept., p. 26, pl. 41, figs. 1-6 from Original Description Citations for the Reptiles and Amphibians of North America © Ellin Beltz
Meaning of the Scientific Name
*Incilius* I can't find a definition of Incilius. Incilius appears to be first used for toads by Cope, 1863. Assuming it's a Latin word, incile or incilis means a ditch or trench. The Latin suffix -ius is used to form adjectives from nouns ( similar to -ious in English.) (Eg. Rex = king, Regius = kingly) Using these roots, Incilius should mean - characterized by a ditch or trench. Toads are often found in ditches with water in them, so this could be the meaning. Or it might refer to a feature on toads, but I can't think of one that fits, other than for toads with cranial crests. *alvarius* arius - belonging to alvus - the womb or belly from Scientific and Common Names of the Reptiles and Amphibians of North America - Explained © Ellin Beltz
Related or Similar California Frogs
Anaxyrus boreas halophilus - California Toad Anaxyrus woodhousii - Rocky Mountain Toad Anaxyrus cognatus - Great Plains Toad Anaxyrus punctatus - Red-spotted Toad
More Information and References
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. Flaxington, William C. Amphibians and Reptiles of California: Field Observations, Distribution, and Natural History. Fieldnotes Press, Anaheim, California, 2021. Samuel M. McGinnis and Robert C. Stebbins. Peterson Field Guide to Western Reptiles & Amphibians. 4th Edition. Houghton Mifflin Harcourt Publishing Company, 2018. 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. Degenhardt, William G., Painter, Charles W. , & Price, Andrew H. Amphibians and Reptiles of New Mexico. University of New Mexico Press, 1996 Davidson, Carlos. Booklet to the CD Frog and Toad Calls of the Pacific Coast - Vanishing Voices. Cornell Laboratory of Ornithology, 1995. ¹ Fouquette Jr., Painter, Nanjappa in Lannoo, 2005 Robert C. Thomson, Amber N. Wright, and H. Bradley Shaffer. California Amphibian and Reptile Species of Special Concern. University of California Press, 2016. Joseph Grinnell and Charles Lewis Camp. A Distributional List of the Amphibians and Reptiles of California. University of California Publications in Zoology Vol. 17, No. 10, pp. 127-208. July 11, 1917.

Conservation Status
The following conservation status listings for this animal are taken from the January 2024 State of California Special Animals List and the January 2024 Federally Listed Endangered and Threatened Animals of California list (unless indicated otherwise below.) Both lists are produced by multiple agencies every year, and sometimes more than once per year, so the conservation status listing information found below might not be from the most recent lists. To make sure you are seeing the most recent listings, go to this California Department of Fish and Wildlife web page where you can search for and download both lists: https://www.wildlife.ca.gov/Data/CNDDB/Plants-and-Animals. A detailed explanation of the meaning of the status listing symbols can be found at the beginning of the two lists. For quick reference, I have included them on my Special Status Information page. If no status is listed here, the animal is not included on either 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 also go to the NatureServe and IUCN websites to check their rankings. Special Animals List Notes, January, 2024: "Formerly Bufo alvarius. Between 2006-2009, the scientific name has been changed to Cranopsis alvaria, Ollotis alvaria, Incilius alvarius, back to Ollotis alvarius, and then back to Incilius alvarius. The common name has changed from Colorado River toad to Sonoran Desert toad."
Organization	Status Listing	Notes
NatureServe Global Ranking	G5	Secure
NatureServe State Ranking	SH	All California sites are historical; the element has not been seen for at least 20 years, but suitable habitat still exists.
U.S. Endangered Species Act (ESA)	None
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	LC	Least Concern

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