Home: Species at Risk: Hognose Snake

Western Hognose Snake

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The Plains Hognose Snake reaches the northern limit of its range in Alberta. The species' occurrence in the province is loosely associated with the major river drainages of the extreme southeast comer of the province, as these were no doubt used as post glacial dispersal corridors into the north. Historically, most records have fallen east of a line drawn connecting Orion and Medicine Hat, and south of the Red Deer River. Current records extend this known range to the west, perhaps as far as Rolling Hills. There have also been unconfirmed records of Plains Hognose Snakes from the Dinosaur Provincial Park area and from the Fort Macleod area that, if credible, extend the known limits of this species range in Alberta even further west. The Fort Macleod record, however, given its distance from the known range, may represent a case of species misidentification.

The range of the Plains Hognose Snake in Alberta appears to be discontinuous west from the Cypress Hills area, resulting in what has been historically portrayed as separate populations of this snake in the province. The "south population" occurs in the Milk River Canyon/ Wild Horse/ Manyberries region and is likely contiguous with a Montana population. Meanwhile, the north population is centered along the South Saskatchewan River from the area of Medicine Hat in the south to the area of Empress in the north. Undiscovered populations of this snake may still exist west of the Cypress Hills in suitable habitat along the species' dispersal routes. Conversely, the "north population" of this species in Alberta may be the result of a separate migration of snakes northward through Saskatchewan, and around the east end of the Cypress Hills. Whichever the case, this snake should be looked for in suitable habitat along all of southeast Alberta's post glacial spillway drainages, especially the Etzikom, the Chin, and the Forty Mile Coulees.

It is interesting to note that the bulk of the records for the Plains Hognose Snake in this province fall within the eastern boundary of the range of the Northern Pocket Gopher. The fact that the ranges of these two species closely overlap in the southeast comer of the province may suggest a close association between these two animals in Alberta. The Richardson's Ground Squirrel, in comparison, was largely absent on the study area at Suffield, so it was not possible to determine whether the snakes also favour the colonies of this rodent where their populations overlap. The lack of records points out that the actual range of the Plains Hognose Snake in Alberta has yet to be accurately defined. It is therefore impossible, at present, to determine whether this species has a stable, expanding or contracting range in the province. 

Recent findings that place Plains Hognose Snakes in a broader variety of prairie habitats than was formerly expected are heartening. Based on these findings, potentially suitable areas for this snake exist in large tracts from the area north of, but adjacent to, the Red Deer River, west to at least the longitude of Bassano, and south to the U.S. border. In contrast, the amount of what we consider "pristine" prairie remaining in Alberta is relatively small. If it is shown that the Plains Hognose Snake requires such conditions, then a large portion of the area outlined above would not be suitable habitat, and lightly impacted areas such as Canadian Forces Base Suffield and the Pinhorn Grazing Reserve could be crucial to the survival of this species in Alberta.

Reprinted from Alberta Wildlife Status Report No. 15 (1998), with permission from Alberta Sustainable Resource Development.

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