Ted, I once caught a glimpse of a cougar in the UP. They are around, but not very numerous.

As far as snakes go, if you go very far west in SD, you will find them. They're definitely present on the Ft Pierre Grasslands. My dogs aren't snake broke either. If I go out that way, I use the rattler vaccine. There's some question about how effective it is, but I know a vet out there who recommends it, and another vet from here in WI who uses it on his dogs when he goes on an early prairie grouse hunt.