I saw this little guy in 2006, before I was really deeply into wildlife watching. I saw it at the Calgary Zoo, in Alberta, Canada. It was running through the portion of the zoo located on an island in the Bow River. Unfortunately I don’t have a photo of the tail, and memory serves me poorly as to how long it was proportionately. If anyone can surmise any clues as to the identity of this mustelid from this rather lackluster photo, I would appreciate it!
It’s impossible to be sure, but in my experience, ermines (a.k.a. short-tailed weasels) tend to have more rounded ears. Also, in areas where both they and long-tailed weasels occur, the former tend to inhabit upland habitats while the latter are more common around rivers and lakes. So I’d say long-tailed weasel is more likely. Besides, it looks kind of large compared to the prey (assuming it’s an adult vole, which it might or might not be).
Thank you, that’s kind of my gut feeling. My impression of it was it was quite large, not as large as a mink but nearly so, and the vole seemed to be adult sized.