Arroyo Toad (Anaxyrus californicus)
Federally Endangered (USFWS)
CA Species of Special Concern (CDFW)
The Arroyo Toad (ARTO) is endemic to California and Baja California. As adults, they are primarily active at night while they burrow during the daytime in sandy substrates. Toadlets, newly metamorphosed juveniles, are diurnal. ARTO are active generally from the first substantial rains in January-March through August/September.
The male advertisement call is a fast trill that rises in pitch before stopping suddenly, lasting approximately 10 seconds.
Suitable BREEDING Habitat
ARTO habitat requirements are very specialized as they require exposed sandy banks along streamsides for burrowing, scattered vegetation to use for shelter from predators and increased humidity, and pools of calm water that contain silt-free, sand or gravel bottoms.
Breeding occurs between March through July, where a male selects an ideal breeding site and starts his advertisement call to try and attract a female. The prospective female will go to the male, check him out, and if all goes well, he amplexes her. Approximately 4,700 eggs are laid in very long, double-stranded, chains that are laid along the quiet margins of the nearby shallow stream/pools.
Tadpoles hatch between 4-6 days and stay close to the egg mass for approximately 2 weeks. They start out black in coloration, making them hard to distinguish between small Western Toads. As they grow, they become a very cryptic sandy color in order to blend in with the stream bottom. ARTO tadpoles have highly specialized mouthparts that allow them to sift (the only California tadpole capable of this) the stream bottom for food. Tadpoles metamorphose after 72-80 days from late May to early July.
Toadlets forage during the day on exposed gravel for several weeks before transitioning to becoming nocturnal and burrowing during the day.
To determine presence/absence of a site, at least 6 surveys are conducted during the breeding season between March 15 through July 1, where there are at least 7 days in between each survey round. At least one survey must be conducted during the months of April, May, and June. Each survey round must consist of a daytime and nighttime component within the same 24 hour period. Night surveys must be conducted between one hour after dusk and midnight where ambient temperature at dusk is at least 55 degrees Fahrenheit. Night surveys cannot be conducted during a full moon or near full moon illumination or during adverse weather conditions. It should be noted that receiving negative results during extreme weather conditions (i.e. drought) may yield the year's survey results inconclusive.
ARTO was listed as federally endangered on December 16, 1994. There is currently a petition to downlist the species to threatened and the USFWS is currently reviewing the public comments in response to the petition and expected they would publish the final determination by March 27, 2015. The current status of the petition and the associated documents can be found here.
CaliforniaHerps.com. Anaxyrus californicus- Arroyo Toad. http://www.californiaherps.com/frogs/pages/b.californicus.html 2015.
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.