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Home »» Frogs & Toads »» Budonidae (Toads) »» Black Toad (Anaxyrus exsul)


Black Toad (Anaxyrus exsul)vulnerable species





Description: The toad's black skin is covered in white and tan speckles and it sports a white midline down its spine from head to rump. Adults are approximately 2.0 inches in length. They are active during the warmer months and overwinter underground near their native springs. This species walks rather than hops, and never strays far from water. Male black toads do not have vocal sacs and do not make a real advertisement call, but rather a small chirping noise as a territorial call around other males; much like its close relative the western toad.


Habitat: The Black Toad's primary habitat is watercourses, irrigation ditches, and marshes (grass, sedge, dwarf bulrush, and watercress) formed by waterflow from springs, surrounded by cold desert steppe. Adults are more aquatic than other toad species in California, and breed in shallow marsh and pond waters. The toads retreat to rodent burrows or other refuges in winter. At present, there do not appear to be any major threats to this species. However, potential future threats might include habitat destruction from changes in irrigation schemes or other factors resulting in water table alteration, well-intentioned but non-scientifically based conservation efforts, changes in water availability, recreational vehicle use, collection by humans, changes in grazing regimes and predation by introduced fish. Other desert toads in nearby areas have done well, and even thrived, with more active management. Black toad adults prefer habitats with short plant cover and unobstructed access to still or slowly flowing water. In recent years, fencing some springs to exclude cattle has resulted in an overgrowth of vegetation requiring hand cutting to keep the habitat accessible for toads. The toads have been able to maintain a fairly stable population regardless of changes in agriculture and grazing practices over the past 20 years.


Range: lives only in scattered oases in the Deep Springs Valley of Inyo County, California. In fact, its original scientific name, Bufo exsul, means "exiled toad," which refers to its species' isolation in a tiny spot in the high desert wilderness of the Californian Great Basin.


Found in these States: CA | NV


Diet: The diet of black toads consists mainly of insects. These insectivores eat smaller insects such as ants and beetles. They hunt mainly in the early mornings and late evenings to avoid mid-day heat. The main difference in eating habits between adults and developing young is the size of their prey. Tadpoles feed on organic material and minerals suspended in the water. Younger toads eat ants, wasps, and mites, while fully mature toads eat larger insects such as beetles and Lepidoptera larvae. Diptera, Coleoptera, and Hymenoptera species were present most frequently in adult and juvenile black toad stomachs. Mites and mollusks were found most frequently in juveniles.


Reproduction: Breeding occurs in water sources such as marshy areas and ponds. Black toads are polygynandrous. Due to their lack of vocal sacs, male black toads have a weaker, high pitch release call but do not have a specific advertisement call. Females can also produce release calls. During breeding, black toads join in amplexus where a male attaches to a female's back. Males externally fertilize the female's eggs. Once complete, the eggs are left hidden in vegetation in the water.

Black toad mating season takes place in the spring from March to April. Females are oviparous and iteroparous, meaning that they lay multiple clutches of eggs across multiple seasons. They can ovulate in November, but lay their eggs in the spring. Once external fertilization occurs, eggs are linked together and commonly dropped in close proximity to each other in shallow vegetated areas. Approximately 16,000 eggs are laid at one time, and they take three to five days to hatch. Birth mass has not been reported.

Adults leave their eggs after breeding, young are fully independent upon hatching. There is no reported age at sexual maturity. Once fully developed, the average female snout-vent length is 52 mm while the average male SVL is 50 mm.


Status: The habitat of the black toad is relatively intact, however it is still considered a vulnerable species because although it is abundant within its habitat, the black toad has a very limited range. Deep Springs College continues a program to care for the wild population of this species, and owns much of the land where its habitat is found. Livestock grazing has occurred in much of the toad habitat for more than one hundred years, and grazing, vegetation management, and irrigation have been suggested as possibly increasing the suitable habitat for the species, which breeds in otherwise comparatively rare open water. As noted in the IUCN Red List, the population of this species was reported to be more or less stable in the early 1970s, and no significant change was reported in 1990 or 1999. The population at Antelope Springs was once reported to have died out, but was found by researchers in 2003, and is now apparently thriving where vegetation has been maintained in a suitable state. In 1977 it was estimated that there were more than 80,000 individuals in the population.


Subspecies: None


Taxonomy:

»» Kingdom: Animalia - Animals
   »» Phylum: Chordata - Chordates
     »» Subphylum: Vertebrata - Vertebrates
       »» Class: Amphibia - Amphibians
         »» Order: Anura - Frogs & Toads
           »» Family: Bufonidae - Toads
             »» Genus: Anaxyrus
               »» Species: Anaxyrus exsul - Black Toad
                 »» Subspecies: None

This article uses material from the Wikipedia article "Black Toad", which is released under the Creative Commons Attribution-Share-Alike License 3.0. Content may have been omitted from the original, but no content has been changed or extended.

 

 

 

 


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Disclaimer: ITIS taxonomy is based on the latest scientific consensus available, and is provided as a general reference source for interested parties. However, it is not a legal authority for statutory or regulatory purposes. While every effort has been made to provide the most reliable and up-to-date information available, ultimate legal requirements with respect to species are contained in provisions of treaties to which the United States is a party, wildlife statutes, regulations, and any applicable notices that have been published in the Federal Register. For further information on U.S. legal requirements with respect to protected taxa, please contact the U.S. Fish and Wildlife Service.

 
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