I use a .22 on squirells and rabbits. Possums, Coons, coyotes in close, all get a load of 00 buck from a 1187.
when I was working, and had to put an animal down, I found that .38s 9s, and .40s were not reliable. I was shooting a lot of pit bulls at the time. I once responded to an officer needs assistance call to find a cop standing on the roof of her cruiser trying to shoot two pit bulls who had her surrounded. Her Sig P226 with Federal 165gr hollowpoints seemed to just bounce off those big thick chests and heads. I got out of my car, shotgun in hand, and finalized the disposition of the call. Ever since then, the 12 gauge is my go to critter gun under 50 yards. (slugs on the side saddle.) Longer shots seldom present at my house, but if they did, it would be 5.56.