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A Guide to the Amphibians
and Reptiles of California


Arizona Toad - Anaxyrus microscaphus

(Cope, 1866)

(= Bufo microscaphus)
Click on a picture for a larger view



Arizona Toad California Range Map
Possible Former Range in
California
: Red



Listen to this toad:

speaker
One short call



observation link





Formerly present, possibly extirpated in California.

All toads shown here were found outside California.
Arizona Toad Arizona Toad Arizona Toad
Adult, Washington County, Utah Adult, Washington County, Utah
Arizona Toad Arizona Toad Arizona Toad
Adult, Washington County, Utah Adult, emerging from the sand at sunset, Washington County, Utah Adult, Washington County, Utah
Arizona Toad Arizona Toad Arizona Toad
Adult, Yavapai County, Arizona Adult, Arizona. Arizona-Sonora
Desert Museum
Arizona Toad Arizona Toad Arizona Toad
Adult, Washington County, Utah
Underside of adult
   
Juveniles
Arizona Toad Arizona Toad  
Juvenile, Washington County, Utah
 
   
Possible California Habitat
Arizona Toad Habitat Arizona Toad Habitat Arizona Toad Habitat
Possible habitat along the Colorado River near Needles, San Bernardino County
Possible habitat near the Colorado River near Fort Mojave, San Bernardino County
   
Short Videos
Arizona Toads Arizona Toad Arizona Toad
Several male Arizona Toads calling and interacting at night at the edge of a small creek next to a river in Washington County, Utah, including two examples of a male attempting amplexus with another male who then makes release calls. Canyon Treefrogs can be heard in the background.
A short example of a male calling at night. Several Arizona Toads seen hanging around the edge of a small creek at night in Washington County, Utah.
Arizona Toad Arizona Toad  
A male gives a release call 
when he is picked up.
Tiny recently-metamorphosed toadlets hop and swim around a breeding creek full of tadpoles of several species of frogs and toads.  
     
Description
 
Size
Adults are 1.8 - 3.4 inches from snout to vent (4.6 - 8.6 cm). (Stebbins, 2003)

Appearance
A plump, stocky toad with dry, skin with low warts and few tubercles. No cranial crests. Oval, widely separated parotoid glands that are pale toward the front. Pupils are horizontal.
Color and Pattern
Color is usually gray, but can be beige, pale yellow, pink, rusty, and brown.
There is no stripe down the middle of the back.
Often paler on front of parotoids, upper eyelids, and central upper back.
Whitish below, with no spots or mottling.
Male and female throats are pale.
(Has fewer warts and spots and tubercles than related A. californicus.)
Young
Young are salmon-colored or light olive with reddish warts.

Life History and Behavior
Activity
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.
Movement
Moves by hopping instead of walking.
Defense
Like most toads do for defense, this toad relies on parotoid glands and warts which can secrete a poison that deters some predators.
Longevity
Probably 4 - 5 years.
Voice (Listen)
A loud, fast high-pitched trill averaging 5.7 seconds in length, rising in pitch, and ending abruptly. Calls are made at night.
Diet and Feeding
Diet consists of a variety of invertebrates.
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.
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 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 takes place from early to Late February at some locations, and late March to early April at higher-elevation locations, ending as late as July. Breeding is not dependant on rainfall, but by warming temperatures and water levels. Spring flooding delays breeding. Breeding may occur for 10 - 12 days at a location, then stop due to rain and floods, and continue again following warmer drier weather.

Breeding sites are shallow stream edges and side pools with minimal current. Males gather at a breeding site and make an advertisement call to attract females, but many males are satellite breeders, either searching for females, or waiting and grabbing a female who is attracted to another male's call.
Eggs
Egg strings are laid on the bottom of pools.
An average of 4,500 eggs per clutch has been estimated. (Schwaner and Sullivan in Lanoo, 2005)
Eggs hatch in 3 - 6 days.
Tadpoles and Young
Tadpoles undergo metamorphosis 3 - 4 months after hatching, depending on varying environmental conditions.
Predation and flooding can cause high tadpole mortality.

Hybrids
Hybridizes with A. woodhousii in some areas.

Habitat
Inhabits riparian areas from lowlands near the Colorado River drainage in California, into uplands and pine-oak woodland.

Geographical Range
The overall range of this toad is fragmented, from the Colorado River drainage near Fort Mojave, east across central Arizona into western New Mexico, and around the area where the Nevada, Utah, and Arizona borders meet.

In his 1972 book California Amphibians and Reptiles, Robert Stebbins states that this toad is present at the Colorado River near Needles, but I have not yet found any records of museum specimens from that area of California. In the range map of his subsequent 2003 field guide, Stebbins does not indicate that B. microsacphus occurs (or even formerly occured) in California. Many sources do show the range of this toad extending into California, as in this US Forest Service map, and this IUCN map.

I list the species as formerly present in California due to these and other indications of its occurance in California across the Colorado River from known populations around Fort Mojave, Arizona. More recent range maps which do not show this species occurring in California are interpreted as illustrating that the species no longer occurs in the state due to habitat alteration.

Full Species Range Map
Elevational Range
From 600 - 6,000 ft. (190 - 1,829 m.) (Stebbins, 2003)

Notes on Taxonomy

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

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.


Alternate and Previous Names (Synonyms)

Fort Mojave Toad

Bufo microscaphus - Arizona Toad (Stebbins 2003)
Bufo microscaphus microscaphus - Arizona Toad (Stebbins1954, 1966, 1985)

Conservation Issues  (Conservation Status)
I can't find any information about the current presence and status of this toad in California. It has been estimated to be absent from 75% of its historic range, but others note that a general decline has not occurred throughout Arizona. Impoundments which restrict the flow of stream water, create quiet waters which are more favored for breeding by a competing toad species, A. woodhousii, with which A. microscaphus hybridizes. Introduced predators, land alteration, and human recreational land use may also contribute to declines.
Taxonomy
Family Bufonidae True Toads Gray, 1825
Genus Anaxyrus North American Toads Tschudi, 1845
Species microscaphus Arizona Toad

(Cope, 1866)
Original Description
Cope, "1866" 1867 - Proc. Acad. Nat. Sci. Philadelphia, Vol. 18, Oct., p. 301

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
microscaphus - mikros -
Greek - small
                          skaphis
Greek - shovel - refers to this toad's tarsal spade

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 californicus - Arroyo 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.

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.

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 come from the Special Animals List and the Endangered and Threatened Animals List which are published by the California Department of Fish and Wildlife.


This toad is not on the Special Animals List, meaning there are no significant conservation concerns for it in California according to the Dept. of Fish and Game. However, this might be because they do not recognize it as a distinct species. If it still occurs in California, this toad is definitely at risk.



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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