E-Fauna BC: Electronic Atlas of the Wildlife of British Columbia

Anaxyrus boreas Baird & Girard, 1852
Boreal Toad; Western Toad
Family: Bufonidae

Species account author: Prepared with contributions by Hugh Griffith and Brent Matsuda.

© Larry Halverson  Email the photographer   (Photo ID #1194)

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Distribution of Anaxyrus boreas in British Columbia
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AmphibiaWeb US Distribution Map

Introduction


The Western Toad is found in North America from Alaska and the Yukon south to Baja, California (Mexico). It is found throughout British Columbia. Two subspecies are recognized for this species, with one subspecies found in British Columbia: Anaxyrus boreas boreas (Boreal Toad).

Species Information

The Western Toad is in the family Bufonidae, the true toads. Toads are easily recognized by their relatively short limbs and rough, warty skin that typically appear as spots on the body. Behind the eyes are prominent parotoid glands, which can exude a toxin as a defensive measure. Toads are more terrestrial than frogs, and can be found relatively far from permanent bodies of water. Twenty-five species of the genus Bufo occur in North America (Natureserve Explorer, 2005), but B. boreas is the only Bufonid toad found in British Columbia.

The BC Frogwatch Program (BC Ministry of Environment 2009) descibes Western Toads as follows: 'Adult Western Toads have stocky bodies with short legs, and tend to walk rather than hop. Their thick skin appears dry and bumpy and can range in colour from pale green to grey, dark brown, and red. They typically have pale-coloured bellies mottled with black, and a pale coloured stripe down their backs. Their beautiful gold-flecked eyes have distinctive horizontal oval pupils. Behind each eye is a prominent oblong or kidney-shaped swelling called a parotoid gland. Adults range from 5.5 to 14.5 centimetres in body length, excluding the hind legs. Males are generally smaller than females and have dark pads on their thumbs that help them cling to the female during mating. Their skin is usually less rough and blotched than the females' skin.'

Western Toads are mostly nocturnal, but can be found during the day at higher elevations and latitudes (BC Ministry of Environment, 2009).

Identification and Subspecies Information

Biology

Reproduction

Adult Western Toads migrate to communal breeding sites in early spring' (BC Ministry of Environment 2009), and congregate in small ponds and pools (Matsuda et al. 2006). They are reported to return to the same breeding sites each year (Matsuda et al. 2006). Females lay eggs in long strings (several metres long) that are wrapped around vegetation. A female can produce up to 12,000 eggs in a single clutch, and these hatch in seven to ten days, developing into toadlets in six to ten weeks (Matsuda et al. 2006). As they transform, they gather along the edges of breeding ponds. Tiny toadlets emerge on mass, usually in early July, and disperse overland. At this stage, they are so small that they are easily trampled and are also easy prey. Later in the summer they are easily recognizable by their bright yellow foot tubercles.
Diet

Western Toads eat a variety of insects and invertebrates. Over 95 percent of their adult diet consists of flying insects, ants, beetles, sowbugs, crayfish, spiders, centipedes, slugs, and earthworms, while tadpoles feed on aquatic plants and algae (BC Ministry of Environment 2009).

Habitat


Western Toads breed in a variety of natural and artificial aquatic habitats, with or without tree or canopy cover, coarse woody debris, or emergent vegetation (Wind and Dupuis, 2002). Although they disperse widely, Wester Toads prefer damp conditions, and will either dig their own burrows, or take shelter in small mammal burrows, beneath logs and within crevices: they hibernate in burrows below the frostline, up to 1.3 metres below ground (BC Ministry of Environment 2009).

Distribution


The Western Toad can be found from sea level to elevations of several thousand feet. The historical range of this species includes the Pacific Coast from Baja California, Mexico to Alaska and southern areas of the Yukon Territory. It is found in parts of Nevada, Colorado, Utah and Montana, western Alberta, and most of B.C., excluding much of the northern interior. The Western Toad is the only amphibian native to Haida Gwaii (Matsuda et al. 2006).

Conservation

Conservation Concerns

There have been significant losses throughout the overall distribution, as populations have declined or been extirpated. Western Toads are explosive breeders, many females laying eggs at same time, which can result in population crashes if breeding sites are subject to random extremes in weather, or harmful anthropogenic activities. The stocking of lakes with game fish is thought to be a major threat to toads, either through larval predation or introduction of non-native pathogens with the fish (Wind and Dupuis, 2002). Toadlets tend to emerge en masse, and dozens or even hundreds of tiny, newly metamorphosed “toadlets” can be found dispersing over an area shortly after emerging from their aquatic tadpole stage. Like any amphibian, toads can experience high mortality on roadways, particularly when these newly metamorphosed toadlets are dispersing. This also makes them more vulnerable to predation. Probably the biggest threat to toads in B.C., as in all amphibians, is habitat loss and fragmentation. The draining and elimination of wetlands has removed breeding sites, and the criss-crossing of natural ranges by roads and other barriers prevents re-establishment of depleted or extirpated populations

Status Information

Origin StatusProvincial StatusBC List
(Red Blue List)
COSEWIC
NativeS4YellowSC (Nov 2012)
BC Ministry of Environment: BC Species and Ecosystems Explorer--the authoritative source for conservation information in British Columbia.

Additional Notes

Western Toads are nocturnal at low elevations and diurnal at higher elevations (AmphibiaWeb 2009).

Tiny, newly transformed Western Toads leave their nursery ponds and lakes in late June and early July, heading for their summer and winter territories. During this period, they move over the ground in the thousands, and are very much at risk from trampling and crushing by vehicles and pedestrians.

Synonyms and Alternate Names

Bufo boreas Baird & Girard, 1852

Additional Range and Status Information Links

Additional Photo Sources

Species References

Matsuda, Brent, David M. Green, and Patrick T. Gregory. 2006. Amphibians and Reptiles of British Columbia. Handbook. Royal BC Museum, Victoria.

General References


Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2017. E-Fauna BC: Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. [Accessed: 25/05/2018 3:44:28 PM]
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