The western toad (Anaxyrus boreas) is a large toad species, between long, native to western North America. A. boreas is frequently encountered during the wet season on roads, or near water at other times. It can jump a considerable distance for a toad. Breeding occurs between March and July in mountainous areas, and as early as January in lower-elevation regions. The female lays up to 17,000 eggs stuck together in strings that adhere to vegetation and other objects along water edges.
Description
It has a white or cream dorsal stripe, and is dusky gray or greenish dorsally with skin glands concentrated within the dark blotches. Its parotoid glands are oval, widely separated, and larger than the upper eyelids. It has a mottled venter and horizontal pupils but lacks cranial crests. Compared to females, males have smoother skin, reduced dorsal blotching, and nuptial pads (thickened skin) on their forefeet during breeding season. In juveniles of this species, the dorsal stripe is weak or absent. Large young have prominent dorsal and ventral spotting and yellow feet.
Subspecies
There are two known subspecies of the western toad and the ranges of subspecies are as follows:
Distribution
The range of the western toad extends from western British Columbia and southern Alaska south through Washington, Oregon, and Idaho to northern Baja California, Mexico; east to Montana, western and central Wyoming, Nevada, the mountains and higher plateaus of Utah, and western Colorado. Occurrences of the boreal toad from Yukon Territory, the Northwest Territories, and northwestern and north-central British Columbia have been reported. Southern records of boreal toads in New Mexico have been published, but the species is considered extirpated from the state, with a reintroduction in progress.
Habitat
The boreal toad is found in the Rocky Mountains in aspen (Populus spp.) groves and riparian forests. In Colorado, the largest populations are typically found in areas characterized by willows (Salix spp.), bog birch (Betula glandulosa), and shrubby cinquefoil (Potentilla fruticosa). In the Pacific Northwest, the western toad occurs in mountain meadows and less commonly in Douglas-fir forests (Pseudotsuga menziesii).
In California, optimum habitat for the western toad includes wet or dry mountain meadows or riparian deciduous forest with available open water for breeding. Suitable habitat includes blue oak (Quercus douglasii) savanna, gray pine-oak forest (Pinus sabiniana-Quercus spp.), mixed conifer forest, and alpine meadows. Marginal habitats include annual grasslands, chaparral, ponderosa pine forests, California black oak woodlands, Jeffrey pine forests, and red fir forests.
In the Sierra Nevada, the western toad occurs in mid-elevation pine forests (including Jeffrey pine (Pinus jeffreyi) at higher elevations and ponderosa pine (Pinus ponderosa) at lower elevations), California black oak woodlands (Quercus kelloggii), giant sequoia groves (Sequoiadendron giganteum), montane fir forest (which includes white fir (Abies concolor), red fir (Abies magnifica), and western white pine (Pinus monticola), and redwood forest (Sequoia sempervirens). It is also found in riparian areas within sagebrush-pinyon communities (Artemisia spp.-Pinus spp.), oak-pine woodland and savanna (including coast live oak (Quercus agrifolia), interior live oak (Quercus wislizenii), and canyon live oak (Quercus chrysolepis), and California coastal forest and scrub.
Western toads have been collected from sedge meadows near a pond occurring in a creosotebush (Larrea tridentata) community, and from aspen (Populus spp.)-willow groves within big sagebrush (Artemisia tridentata)-grassland.
Life cycle
Western toads are active from January to October, depending on latitude and elevation, and hibernate over the winter. Boreal toads in one Colorado population used natural chambers near a small stream bed. The high water table, constantly flowing stream, and deep winter snow served to maintain the air temperature within the hibernaculum at a point slightly above freezing. Emergence from hibernation followed a few days of warm temperatures that freed the entrance and increased temperatures within the chamber to about .