Western Toad
Anaxyrus boreas
Western Toad
Anaxyrus boreas
Other names: Bufo boreas, Boreal Toad, Northwestern Toad
The Western Toad is a medium-large sized toad reaching up to 14.5 cm in length, with females growing larger than males. Characteristic of toads, it has dry, warty skin and relatively short limbs. There are prominent parotid glands behind the eyes that can expel a toxin when threatened. Western Toads lack cranial crests that are typical of other toad species in Canada. Western Toads are usually green or brown with a light strip down the middle of the back. The warts and are often reddish and may be circled by black rings. The belly is a dull white with dark mottling. The eyes are gold-flecked and have distinctive horizontal oval pupils. Western Toad tadpoles have long tails with a large fin and are usually black with cloudy tails and no patterning. Tadpoles will grow up to 4 cm before metamorphosis.
Listen to the Indigenous words for “frog” here!
Western Toad Call
The breeding call of the Western Toad is a quiet peeping, like little chicken chicks.
The Western Toad is the only true toad found in British Columbia. In British Columbia, the Western Toad may resemble the Great Basin Spadefoot. The Great Basin Spadefoot lacks parotid glands and has vertical pupils.
Western Toad
Great Basin Spadefoot
The Western Toad has a historical range along the entire Pacific Coast from Baja California to Alaska and southern areas of the Yukon and parts of Alberta. In British Columbia, it is found throughout the province with the exception of the extreme northeast corner. Western Toads are the only amphibian native to Haida Gwaii.
In Canada, Western Toads hibernate during the winter and are active from March until October, depending on latitude and elevation. Individuals often return to the same breeding sites year after year, and may make substantial migrations between breeding sites, summer habitats, and hibernation sites. Toads are more terrestrial than frogs and can be seen quite far from permanent water bodies. The Western Toad can breed in a variety of natural and artificial habitats, with or without tree canopy cover, coarse woody debris, or emergent vegetation. The preferred breeding areas are shallow aquatic habitats with sandy substrates. In the northern part of their range, they are commonly found breeding in beaver ponds. Despite their tolerance of drier conditions, Western Toads prefer damp conditions and will dig their own burrows or use small mammal burrows to escape the heat and to take shelter in moist soils. They will generally hibernate in burrows or cavities that dip below the frostline, up to 1.3 m below ground.
Adult Western Toads migrate to communal breeding areas in early spring, congregating in small ponds and pools. Males call to attract females during the breeding season from April to early June. Fertilization occurs externally in aquatic habitats; the female lays eggs while the male grasps her in . The female will lay up to 12,000 eggs in two long strings that may be over 20 m in length. Eggs develop rapidly and hatch within 2 weeks, but sometimes as early as 3 days. Tadpoles transform into juvenile toads within 4-12 weeks, depending on water temperature. Males reach sexual maturity after 3-4 years, while females do not reach sexual maturity until 4-6 years of age. The lifespan of the Western Toad is over 10 years.
Over 95% of the adult Western Toad diet is flying insects, ants, beetles, sowbugs, crayfish, spiders, centipedes, slugs, and earthworms. Tadpoles feed on aquatic plants and algae.
Western Toads have seen significant losses throughout their overall distribution, although there is little evidence of major declines in Canada. Western Toads are explosive breeders with many females laying eggs at the same time which can lead to population crashes if breeding sites are impacted by random catastrophes like extreme weather or large-scale anthropogenic disturbance. Intense UV radiation may also impact the hatching success of Western Toads. Game fish that are stocked in lakes where Western Toads occur may be a major threat as fish may predate tadpoles and introduce pathogens. Due to the dense migration of newly transformed toadlets, roads and cars may cause high levels of mortality to migrating individuals. The biggest threat to Western Toads in British Columbia is habitat loss and fragmentation. The draining and eradication of wetlands removes breeding sites, and reduces the potential for re-establishment of depleted or extirpated populations. Pathogens, such as Chytrid fungus and Ranavirus, can cause mass mortality of frog and toad populations. Although these pathogens are present in Western Toad populations in Canada, population decline and extirpation from disease outbreaks appears to be rare.
Description
Other names: Bufo boreas, Boreal Toad, Northwestern Toad
The Western Toad is a medium-large sized toad reaching up to 14.5 cm in length, with females growing larger than males. Characteristic of toads, it has dry, warty skin and relatively short limbs. There are prominent behind the eyes that can expel a toxin when threatened. Western Toads lack cranial crests that are typical of other toad species in Canada. Western Toads are usually green or brown with a light strip down the middle of the back. The warts and parotid glands are often reddish and may be circled by black rings. The belly is a dull white with dark mottling. The eyes are gold-flecked and have distinctive horizontal oval pupils. Western Toad tadpoles have long tails with a large fin and are usually black with cloudy tails and no patterning. Tadpoles will grow up to 4 cm before metamorphosis.
Listen to the Indigenous words for “frog” here!
Western Toad Call
The breeding call of the Western Toad is a quiet peeping, like little chicken chicks.
Similar Species
The Western Toad is the only true toad found in British Columbia. In British Columbia, the Western Toad may resemble the Great Basin Spadefoot. The Great Basin Spadefoot lacks parotid glands and has vertical pupils.
Western Toad
Great Basin Spadefoot
Distribution
The Western Toad has a historical range along the entire Pacific Coast from Baja California to Alaska and southern areas of the Yukon and parts of Alberta. In British Columbia, it is found throughout the province with the exception of the extreme northeast corner. Western Toads are the only amphibian native to Haida Gwaii.
Habitat
In Canada, Western Toads hibernate during the winter and are active from March until October, depending on latitude and elevation. Individuals often return to the same breeding sites year after year, and may make substantial migrations between breeding sites, summer habitats, and hibernation sites. Toads are more terrestrial than frogs and can be seen quite far from permanent water bodies. The Western Toad can breed in a variety of natural and artificial habitats, with or without tree canopy cover, coarse woody debris, or emergent vegetation. The preferred breeding areas are shallow aquatic habitats with sandy substrates. In the northern part of their range, they are commonly found breeding in beaver ponds. Despite their tolerance of drier conditions, Western Toads prefer damp conditions and will dig their own burrows or use small mammal burrows to escape the heat and to take shelter in moist soils. They will generally hibernate in burrows or cavities that dip below the frostline, up to 1.3 m below ground.
Reproduction
Adult Western Toads migrate to communal breeding areas in early spring, congregating in small ponds and pools. Males call to attract females during the breeding season from April to early June. Fertilization occurs externally in aquatic habitats; the female lays eggs while the male grasps her in . The female will lay up to 12,000 eggs in two long strings that may be over 20 m in length. Eggs develop rapidly and hatch within 2 weeks, but sometimes as early as 3 days. Tadpoles transform into juvenile toads within 4-12 weeks, depending on water temperature. Males reach sexual maturity after 3-4 years, while females do not reach sexual maturity until 4-6 years of age. The lifespan of the Western Toad is over 10 years.
Diet
Over 95% of the adult Western Toad diet is flying insects, ants, beetles, sowbugs, crayfish, spiders, centipedes, slugs, and earthworms. Tadpoles feed on aquatic plants and algae.
Threats
Western Toads have seen significant losses throughout their overall distribution, although there is little evidence of major declines in Canada. Western Toads are explosive breeders with many females laying eggs at the same time which can lead to population crashes if breeding sites are impacted by random catastrophes like extreme weather or large-scale anthropogenic disturbance. Intense UV radiation may also impact the hatching success of Western Toads. Game fish that are stocked in lakes where Western Toads occur may be a major threat as fish may predate tadpoles and introduce pathogens. Due to the dense migration of newly transformed toadlets, roads and cars may cause high levels of mortality to migrating individuals. The biggest threat to Western Toads in British Columbia is habitat loss and fragmentation. The draining and eradication of wetlands removes breeding sites and reduces the potential for re-establishment of depleted or extirpated populations. Pathogens, such as Chytrid fungus and Ranavirus, can cause mass mortality of frog and toad populations. Although these pathogens are present in Western Toad populations in Canada, population decline and extirpation from disease outbreaks appear to be rare.
Did You Know?
Unlike most toads, Western Toads walk rather than hop.
When threatened, Western Toads sometimes display a defensive posture by raising up on their legs and puffing up with air, making it more difficult for predators to swallow them.
Newly transformed Western Toads are very tiny and leave their nursery ponds en masse in late June or early July to find summer and winter territories. During these migrations they may cover the ground or roads by the thousands, leading to some major roads and highways being temporarily closed for “toad crossings”!