The prairie rattlesnake occurs in SE British Columbia, far southern Alberta and Saskatchewan. Studies aimed at sustainability and protection of habitat are ongoing in Alberta.

The largest predator in Alberta is the cougar or mountain lion, the largest subspecies in North America is resident here. Licensed winter hunting is (unfortunately) available.
A cougar recently made a kill (deer) on my daughter's place near Calgary. Her camera set-up caught the cougar. See http:wareabouts.ca/cougar.html