Unless y'all have some scary huge minks over there, I think a 2 1/2 inch wide bite is a bit large for a mink... but it does seem to fall into the range for otters, at least the otters we have here. Also, otters are a bit more at home in the water than minks are, so I'm going to tentatively say "otters done it".
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“Trouble rather the tiger in his lair than the sage among his books. For to you kingdoms and their armies are things mighty and enduring, but to him they are but toys of the moment, to be overturned with the flick of a finger.”
― Gordon R. Dickson, Tactics of Mistake
― Gordon R. Dickson, Tactics of Mistake