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Canadian Toad

Canadian Toad DrawingThe Canadian Toad (Bufo hemiophrys), sometimes considered a subspecies of the American Toad (Bufo americanus), is one of three species of the genus Bufo found in Alberta, along with the Western Toad (Bufo boreas) and the Great Plains Toad (Bufo cognatus). The Canadian Toad was once a common inhabitant of the northern Interior Plains, and was not considered to be declining in Canada as recently as the mid-1980s. Over the past 10 years, however, Canadian Toads have declined sharply in numbers or disappeared in some areas of central Alberta and populations in other areas of the range such as Manitoba and Wyoming may be declining as well. In Alberta, the Canadian Toad is included on the Red List of species that current information suggests are at risk of declining to nonviable population levels in the province.

Relatively little is known about the habitat requirements of Canadian Toads. The species has historically been found in grassland, aspen parkland, and boreal forest regions across its range. The Canadian Toad is thought to be more aquatic than other bufonids. For example, Canadian Toads are found frequently in meadows and willow bogs near water in northeastern Alberta, and are the only toad species occupying a habitat of plentiful wetlands amid tall grass prairie, aspen and willow in northwestern Minnesota. 

Wetlands occupied by Canadian toads sometimes contain little or no vegetation, and may have currents and high wave action. In some of these habitats, Canadian Toads may be the only species of amphibian present. Although the Canadian Toad appears to be more aquatic than other toads in Alberta, the species spends only about two months of the year (breeding season) in the water or in adjacent riparian habitats. After the breeding season, individuals tend to move to the upslope areas, where they remain until the following breeding season.

Canadian Toads move to the hibernation site by early to mid-September in Alberta and the Northwest Territories, but such movements may begin as early as late August in Minnesota. Adults tend to begin hibernating earlier than juveniles. Both age classes show strong homing abilities to specific wintering sites. In northern regions, hibernacula often contain many individuals. For instance, aggregations of several hundred individuals have been observed near the Alberta/Northwest Territories border, and in Minnesota. Individuals occupy separate burrows within wintering sites, and may change depth in response to soil temperatures. Individual burrows as deep as 117 centimetres have been reported.

Emergence, which occurs over a five to six week period, begins in late April and peaks in mid-may. Adults tend to emerge earlier in the spring than juveniles, and males tend to emerge slightly earlier than females.

Reprinted from Alberta Wildlife Status Report No. 12 (1998), with permission from Alberta Sustainable Resource Development.

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