The Decline of The Canadian Toad

The Decline of The Canadian Toad in Alberta was first noted in the mid 1980's by Roberts (1992,1994). In an overview of the status of amphibians and reptiles in Alberta Cottonwood Consultants (1986) noted that there was no problem apparent up to this time. Russel and Bauer (1993) made the observation that the Canadian Toad at Elk Island National Park declined between 1971 and the mid 1980's and that this was typical of the decline elsewhere in central Alberta. This is based on two reports one made well before the decline and one made during or after the decline. 1971 report by Dierdre Grifiths and 1980. The decline did not occur within the 1970's and the available evidence from many sites in central Alberta suggests that populations of this species remained robust until the 1980's and some into the early 1990's

The decline of this species was first noted along a transect running east and west from near Big Valley to The Red Deer River about 10 km NW of Innisfail Alberta. Sites along this transect were visited on a weekly (or bi-weekly) basis from April to October from 1980-1994. The presence of Canadian toads was noted on the basis of calling males during the spawning period (April -June) and observations of adults and sub adults seen in terrestrial (riparian) habitat, tadpoles, and recently transformed toadlets from June to late summer. During the early 1980's many sites were home numerous adult and sub adult toads and large herds of toadlets in midsummer indicated that reproduction was successful. During the early and mid 1980's low numbers of Canadian Toads were noted at a few sites west of Innisfail along the Red Deer River but it was not until the latter years of the decade that it became apparent that entire populations had disappeared.(for example along the lower Medicine River and adjacent portions of the Red Deer River).

Skeptics and the scientifically cautious will frequently point out that animal populations typically fluctuate in size; sometimes in an irregular fashion and sometimes in a rather regular cycle. What we are seeing with the Canadian toad is the complete disappearance of many breeding populations of this species over large geographic areas. The habitat within this area is often shared with other anurans such as the wood frog and boreal chorus frog which not only persist in these habitats but have shown increases in numbers during the past few years.

Wayne Roberts June 1995

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