Description A medium sized toad with relatively short limbs, it is stocky and blunt-nosed. It has oval parotoid glands, and its cranial crests are weak or not present. The warts are small and dark. The skin varies from light tan to light olive with darker blotching. Underside a uniform, lighter color than dorsal surface. All Arroyo Toads possess a distinctive light colored "V"-shaped stripe spanning the eyes (Fisher and Case 1997; Stebbins 1985).
The Arroyo Toad occurs exclusively in streams in southern California and northwestern Baja California, Mexico.
Life History, Abundance, Activity, and Special Behaviors The Arroyo Toad is found near streams and pools with slow-moving shallow areas. Adults burrow in sandy soil near water during the day, and hunt nocturnally. Breeding begins in April and lasts until July. The male call is a high musical trill (Myers 1930).
Juveniles remain near their pools of origin (due to lack of burrowing ability) for 3 to 8 weeks, then disperse to surrounding shady areas and burrow for winter season. Toads normally require 2 years to reach breeding maturity (Fisher and Case 1985). The longevity of this species is presently unknown.
The larvae require sandy bottom streams with nutrient sediment for filter feeding. After approximately 3 weeks of development, the tadpole's black coloration changes to a mottled brown, to blend in with the sandy bottom where they live (Fisher and Case 1985).
Trends and Threats Threats: Damming water systems or otherwise destroying shallow sandy habitat. Illegal collection. Predation on larva by exotic fish (Jennings and Hayes 1994). Predation by bullfrogs.
The Arroyo Toad has been extirpated from an estimated 75 percent
of its former range. Threats to the survival of this species include:
habitat degradation (from off-road vehicle use and damming of creeks),
predation on larvae by exotic fish, and small population sizes
(Jennings and Hayes 1994), and predation by introduced bullfrogs (Rana catesbeiana. Only 6 of the 22
extant populations south of Ventura are known to contain more than a
dozen adults (Jennings and Hayes 1994).
Relation to Humans Collecting of this species is one of the greatest threats to its survival, and therefore the U.S. Department of Fish and Wildlife keeps the specific locations of populations confidential.
Possible reasons for amphibian decline
Intensified agriculture or grazing Urbanization Disturbance or death from vehicular traffic Mining Predators (natural or introduced)
Comments Anaxyrus californicus has been classified as a distinct species, separate from A. microscaphus due to both morphological
(Myers 1930) and genetic differences (Gergus 1998).
Rescuing an endangered Arroyo Toad from a bullfrog which had eaten it, by cutting it out of the stomach of the euthanized bullfrog (warning: blood).
Runtime: 2:08. Language: English.
Video submitted by: Robert Fisher.
This species was featured as News of the Week on 2 July 2018:
How amphibians will respond to ongoing climate change is uncertain and doubtless will vary among taxa and environments. A study of the Arroyo Toad (Anaxyrus californicus) examined skeletochronology and marked populations to determine age of individuals and age-related population structure of local populations in their environment in coastal southern California (Fisher et al. 2018). This area is affected by periodic multiyear droughts. Age structure of populations of toads in areas of predictable water availability is younger than for areas of surface water unpredictability. The toads are estimated to live seven to nine years. This means that periods of extreme drought, extending across a number of consecutive years, might surpass the life span of frogs. Amphibians such as Arroyo Toads are thus vulnerable to local and regional extinction in ephemeral freshwater systems (Written by David B. Wake).
Fisher, R. N., and Case, T. J. (1997). A Field Guide to the Reptiles and Amphibians of Coastal Southern California. Lazer Touch, San Mateo, California.
Gergus, E. W. A. (1998). ''Systematics of the Bufo microscaphus complex: allozyme evidence.'' Herpetologica, 54(3), 317-324.
Jennings, M. R., and Hayes, M. P. (1994). ''Amphibian and reptile species of special concern in California.'' Final Report #8023 Submitted to the California Department of Fish and Game. California Department of Fish and Game, Sacramento, California..
Myers, G. S. (1930). ''The status of the Southern California Toad, Bufo californicus (Camp).'' Proceedings of the Biological Society of Washington, 43, 73-78.
Stebbins, R. C. (1985). A Field Guide to Western Reptiles and Amphibians. Houghton Mifflin, Boston.