The Arizona toad (''Anaxyrus microscaphus'') is a species of toad in the family Bufonidae. It is endemic to the south-western United States, where its natural habitats are temperate lowland forests, rivers and streams, swamps, freshwater marshes, freshwater springs, ponds, open excavations, irrigated land, and seasonally flooded agricultural land.

Taxonomy

The Arizona toad was first described by the American herpetologist

Edward Drinker Cope Edward Drinker Cope (July 28, 1840 – April 12, 1897) was an American zoologist, paleontologist, comparative anatomist, herpetologist, and ichthyologist. Born to a wealthy Quaker family, Cope distinguished himself as a child prodigy interested ...

in 1867. He named it ''Bufo microscaphus'' and the type locality was Fort Mohave, Arizona. It was commonly known as the southwestern toad and for many years, three subspecies were recognized, ''B. m. microscaphus'', ''B. m. californicus'' and ''B. m. mexicanus''. In 1998, the American herpetologist A. W. E. Gergus raised all three to full species status on the basis of

allozyme Alloenzymes (or also called allozymes) are variant forms of an enzyme which differ structurally but not functionally from other allozymes coded for by different alleles at the same locus. These are opposed to isozymes, which are enzymes that perfo ...

evidence, allopatry and morphology. The large genus '' Bufo'' was split by Frost et al. in 2006, with the North American species being included in the genus '' Anaxyrus''.

Description

The Arizona toad grows to a snout-to-vent length of . The dorsal colour is variable but is often gray or beige with reddish-brown warts. The parotoid glands are oval and widely separated and there is often a pale stripe or patch on the head or spine. Juveniles are often salmon-coloured or greenish-brown.

Distribution and habitat

This species' range is continuous along the Virgin River and its tributaries in southwestern Utah, and southern Nevada, and in locations across Arizona and western New Mexico. It is a protected species in Utah, Nevada and Arizona. Protected populations occur in the Virgin River and its tributaries in Zion National Park. The toads are usually found in sandy areas within about of streams, often in locations with flood channels and dense clumps of willow, or on nearby sandy terraces with live oaks and cottonwoods. In Arizona and New Mexico they sometimes occur at higher altitudes, up to about in forested areas in riparian corridors during rainy periods in summer. They also move into irrigated fields after the breeding season is over, and are found around reservoirs, ponds and other impounded areas.

Behavior

Breeding takes place in backwaters, the edges of streams and side-pools. Trees and shrubs growing at the streamside include

Fremont's cottonwood ''Populus fremontii'', commonly known as Frémont's cottonwood, is a cottonwood (and thus a poplar) native to riparian zones of the Southwestern United States and northern through central Mexico. It is one of three species in ''Populus'' sect ...

(''Populus fremontii''), willows (''Salix'' spp.), and seep willows (''Baccharis salicifolia''). Breeding starts in late February in Arizona but does not commence at higher altitudes in Arizona and in Utah until several weeks later. The male's call is a trill lasting about six seconds. Calling males are often outnumbered by satellite males which opportunistically mate with approaching females. Amplexus takes place and a clutch of about 4,500 eggs is laid in shallow water. The eggs take three to six days to hatch and the development period of the tadpoles before

metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some inse ...

depends largely on the water temperature. The tadpoles probably feed on algae and other organisms attached to underwater surfaces but the diet of adults has not been studied. The toads are nocturnal, spending the day in sandy burrows. They enter a state of torpor and remain underground from about September to February. They may live for four or five years and the main cause of mortality is probably predation, with raccoons (''Procyon lotor''), a medium-sized plover the killdeer (''Charadrius vociferus''), and the wandering garter snake (''Thamnophis elegans vagrans'') feeding on the toads.

Status

The population size of the Arizona toad is believed to be decreasing at a slow rate, probably due to human disturbance of their habitat, and in some localities, such as central Arizona, they are being replaced by Woodhouse's toad (''Anaxyrus woodhousii''). One threat faced by the Arizona toad is

hybridization Hybridization (or hybridisation) may refer to: *Hybridization (biology), the process of combining different varieties of organisms to create a hybrid *Orbital hybridization, in chemistry, the mixing of atomic orbitals into new hybrid orbitals *Nu ...

between these two species. They occupy similar habitat but theoretically should not hybridise because they breed at different seasons. However the male Arizona toad has occasionally been observed to mate with the female Woodhouse's toad. The Arizona toad has also been known to attempt mating with the Great Basin spadefoot toad (''Spea intermontana''), the

Great Plains toad The Great Plains toad, ''Anaxyrus cognatus'', is a relatively large species of true toad native to central North America. Distribution The amphibian is native throughout the Canadian Prairies (northern Great Plains) in southern Alberta, Manitoba ...

(''Bufo cognatus''), the

red-spotted toad The red-spotted toad (''Anaxyrus punctatus'', formerly ''Bufo punctatus'') is a toad in the family Bufonidae found in the southwestern United States and northwestern Mexico. Description It is a small toad species growing to in length. It has a f ...

(''Bufo punctatus''), the

canyon tree frog The canyon tree frog (''Dryophytes arenicolor'') is a species of tree frog native to the rocky plateau areas of southern United States, primarily in New Mexico and Arizona, but it also ranges to Utah, Texas, and Colorado, and as far south as the ...

(''Hyla arenicolor''), the

American bullfrog The American bullfrog (''Lithobates catesbeianus''), often simply known as the bullfrog in Canada and the United States, is a large true frog native to eastern North America. It typically inhabits large permanent water bodies such as swamps, po ...

(''Lithobates catesbeiana''), and the lowland leopard frog (''Lithobates yavapaiensis''). The Arizona toad has a wide range and is assumed to have a large total population. It is an adaptable species and able to tolerate some degree of habitat modification so the International Union for Conservation of Nature has assessed it as being of " least concern".

References

* {{Taxonbar, from=Q2237121 Anaxyrus Amphibians of the United States Endemic fauna of the United States Amphibians described in 1867 Taxa named by Edward Drinker Cope Taxonomy articles created by Polbot