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Arroyo toad

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Title: Arroyo toad  
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Subject: Bufo, Julie A. MacDonald, List of threatened reptiles and amphibians of the United States, San Mateo Creek (Southern California), Santa Clara River (California)
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Arroyo toad

Arroyo toad
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Amphibia
Order: Anura
Family: Bufonidae
Genus: Bufo
Species: B. californicus
Binomial name
Bufo californicus
Camp, 1915

Anaxyrus californicus

The arroyo toad (Anaxyrus californicus) (syn. Bufo californicus), is a stocky, blunt-nosed, warty-skinned species of toad, 5 to 7.5 cm (2.0 to 3.0 in) long. It has horizontal pupils, and is greenish, grey or salmon on the dorsum with a light-colored stripe across the head and eyelids. It has light sacral and mid-dorsal patches, large, oval and widely-separated parotoid glands, and weak or absent cranial crests.

The juvenile of this species are ashy-white, olive or salmon on the dorsal side, with or without black spotting. It has red-tipped tubercles on its back.


  • Habitat 1
  • Behavior 2
    • Reproduction 2.1
    • Diet 2.2
    • Defense Mechanisms 2.3
    • Predators 2.4
  • Reasons for being endangered 3
  • Adaptations 4
  • References 5
  • Further reading 6


Anaxyrus californicus prefers sandy or cobbly washes with swift currents and associated upland and riparian habitats, in Southern California and Baja California. An arroyo is also called a wash; it is a dry creek or stream bed. It fills and flows after sufficient rain, but only temporarily during specific seasons. The arroyo toad inhabits these areas alongside rivers with shallow pebble-like rocks near sandy terrains. Adults take refuge into the sandy soil for protection and shelter. Most importantly the sandy soil enables the female adults to safely lay their eggs. Areas with very little to no vegetation are the primary target. The arroyo toad is a terrestrial and freshwater species. They are prominently nocturnal with a breeding season that revolves around the months of late winter and early spring after seasonal rains. This time is the best for males to forage for breeding supplies. Their eggs are laid at the calling sites of males which take place near shallow gravelly areas near sandy terraces as mentioned earlier. The male may stay latched onto the female for days until she disperses the eggs so he can fertilize them. Outside the breeding season the arroyo emphasizes its terrestrial characteristics, traveling over a kilometer from their normal stream sites. During the dry season the arroyo toad goes into a state of hibernation called aestivation to prevent dehydration. This dormant state normally takes place within the soil or clay-like sand and is from August to January. Due to deforestation they live in small isolated populations. These populations change due to climatic conditions, fires and human cause. When its suitable habitat is disturbed it is hard to estimate an accurate population size. The isolated populations of northern and southern Baja has risen excitement as to whether there would be any genetic diversity among the different populations. Different clades have been supported for the species inhabiting Southern Baja. At least three sub species of the Arroyo Toad inhabit Southern Baja, California. The arroyo toad is evaluated as Endangered on the IUCN Red List of Threatened Species because of habitat destruction.



The male Arroyo toad will choose a satisfying spot near a river or water bank where he will make mating calls to attract a female toad. They mate in an amplex position, and the female toad returns to the location to lay her eggs by the water. The eggs are laid in a two-row formation with an average of 4,700 eggs. The placement of the eggs by the water is very crucial due to the water flow: if some of the eggs are too far from hydration they will dry up and die; eggs can also drop into the depth of the water and be eaten by predators.[1] The eggs that survive hatch in between four and six days.


Once the eggs hatch, the larvae feed on microbes found in the sand by the water where they hatch.[1] For the most part, young Arroyo toads feed on ants and other small insects.[2] When they grow their diet changes to feeding on small beetles. The diet of an adult toad usually consists of caterpillars, moths, crickets, snails, and in some instances eggs and larvae of other Arroyo toads.

Defense Mechanisms

The Arroyo toad's defense mechanism is a poisonous skin secretion, to which some common predators such as the garter snake and American Bullfrog have developed immunity. Another method of defense is hiding in vegetation or underwater from attackers.[3]


The Arroyo toad is fairly cryptic, but often vulnerable to a variety of predators. Eggs and larvae are susceptible to being preyed on by fish, other species of frogs (not excluding adult forms of the Arroyo toad), birds, snakes, and insects that inhabit the waters where the eggs and larvae are developing.[3]

Adult Arroyo toads are also vulnerable to predators such as American Bullfrogs and garter snakes. Although they may escape, they have a high likeliness of dying from wounds caused by their attackers (1). The American Bullfrog has a tendency to prey on males during their mating calls, and will attack toads while they are in amplex thereby preventing reproduction rates in the population.[3] This has a great influence on the decrease in the species population number.

Along with natural predators, the Arroyo toad is suffering from human-caused threat due to their influence on the toad's environment. Factors such as urbanization and the building of roads, as well as mining and agriculture are decreasing the size of their habitat, and environmental changes such as droughts and wildfires also cause a disturbance in their population.

Reasons for being endangered

The most important threats to the arroyo toad are due to human activities.[4][5] These activities include encroachment by agriculture, construction of roads, off-road vehicle use, grazing by livestock and mining. All can result in substantial habitat destruction and/or alteration of river hydrology. Other more minor threats are due to introduced nonnative predators such as bullfrogs and predatory fish, invasive nonnative plants, drought, fire and fire suppression, unseasonal water releases from dams, and light and noise pollution from adjacent developments.

On March 27, 2014, the Department of Fish and Wildlife recommended the Arroyo Toad's status be upgraded from Endangered to Threatened. The agency stated that the arroyo toad still faces "significant threats", in particular operation of dams and water diversions; urban development; introduced predator species; and drought. However, they felt that conditions had improved, saying, "The overall magnitude of threats impacting the arroyo toad has decreased since the time of listing, due in part to implementation of conservation and management actions."[6]


Anaxyrus californicus or Arroyo Toad defends itself with a toxin found on the skin. The toxin is released from the parotoid glands which can be identified as pale spots found towards the head. The main component found in the venom is called Bufotoxin. All of the venom found on the toad’s skin is enough to cause serious symptoms or even death in the attacker. Though some natural predators have built an immunity and regularly feed on the toads, their toxin should not be underestimated. If a human comes in contact with the toad’s skin symptoms include: serious irritation and pain to the throat, eyes, nose, and mouth, cardiovascular and respiratory systems, seizures and paralysis, vomiting, hallucinations or even death. There is no anti-venom and treatment varies based on the symptoms exhibited. The Arroyo toad is nocturnal, spending most of the day underground with exception to mating season. During the mating season may be found during the day along the shallows of a pond. It travels by quickly hopping, as opposed to walking or striding. When hunting for food the toad lunges towards the targets, usually ants, and extends its large sticky tongue to trap and consume them.


  1. ^ a b Sweet, Samuel S., and Brian K. Sullivan. "Anaxyrus Californicus." AmphibiaWeb. Berkeley, California, n.d. Web. 27 Oct. 2013.
  2. ^ Hammerson, Geoffrey, and Georgina Santos-Barbera. "Anaxyrus Californicus." (Arroyo Toad). IUCN Red List of Threatened Species, n.d. Web. 15 Oct. 2013
  3. ^ a b c Dodd, C. Kenneth. "Anaxyrus Californicus." Frogs of the United States and Canada. Baltimore: Johns Hopkins UP, 2013. N. pag. Google Books. Web. 24 Oct. 2013.
  4. ^  
  5. ^ United States Fish and Wildlife Service (24 March 2014). Arroyo toad (Anaxyrus californicus) Species Report (PDF) (Report). Prepared by the Ventura Fish and Wildlife Office, Ventura, California. p. 114p. Retrieved 5 July 2015. 
  6. ^  

Further reading

  • Pauly, G. B., D. M. Hillis, and D. C. Cannatella. (2004) The history of a Nearctic colonization: Molecular phylogenetics and biogeography of the Nearctic toads (Bufo). Evolution 58: 2517–2535.
  • Hammerson & Santos-Barrera (2004). Bufo californicus. 2006. IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 11 May 2006. Database entry includes a range map and justification for why this species is endangered
  • This article is based on a description from A Field Guide to the Reptiles and Amphibians of Coastal Southern California, Robert N. Fisher and Ted J. Case, USGS,
  • Sahagun, L. Endangered arroyo toads cling to existence in the Tehachapi Mountains. Los Angeles Times August 26, 2011. Retrieved August 30, 2011.
  • Hammerson, Geoffrey, and Georgina Santos-Barbera. "Anaxyrus Californicus." (Arroyo Toad). IUCN Red List of Threatened Species, n.d. Web. 15 Oct. 2013
  • Miller, David AW, et al. "Joint estimation of habitat dynamics and species interactions: disturbance reduces co‐occurrence of non‐native predators with an endangered toad." Journal of Animal Ecology 81.6 (2012): 1288-1297.
  • Blumm, Michael C., and George A. Kimbrell. "Flies, Wolves, Spiders, Toads, and the Constitutionality of the Endangered Species Act's Take Provision."Environmental Law 34 (2004): 309.
  • Mitrovich, Milan J., et al. "Habitat Use and Movement of the Endangered Arroyo Toad (Anaxyrus californicus) in Coastal Southern California." Journal of Herpetology 45.3 (2011): 319-328.
  • Griffin, Paul C., and Ted J. Case. "Terrestrial habitat preferences of adult arroyo southwestern toads." The Journal of wildlife management (2001): 633-644.
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