I carry a Ruger Redhawk 44 magnum when I hunt in the mountains whether predators are common in the area or not. It is a little heavy, but built like a tank and can shoot some heavy HSM bear loads. I decided on the Ruger over the S&W due to the stronger build on the Rugers. I read somewhere that some S&W revolvers cannot shoot the really heavy and hot for caliber rounds because the frames aren't built for it. In fact, if I remember correctly, its printed on the box of HSM bear loads not to shoot them in S&W revolvers.
I am not sure how "necessary" it is to carry a defensive sidearm for four legged creatures, but everyone else in our hunting party carries one. That said, I also don't live in the mountains where I would be exposed to predators on a daily (or at least frequent) basis. I think it is more of a "better to have it and not need it; than need it and not have it" kind of deal (for me anyway).