Here in the mountains of Arizona (at 6500 ft), we kill 3/4 every year, usually out around the horses. My wife prefers to use a shovel (!), I use a Charter Arms .44 Spl. A shot load #1, JHP's (for 2 & 4 legged varmints) in the other 4. usual shot is 6/7 feet.
Last year, I came across a snake where the front 1/2 was bright red, and the back 1/2 was rattler. It was very aggressive, and two shot loads had no apparent effect - it continued to come towards me and my dogs. I put the dogs in the house, and got my friend Mr. Remington 870. A load of #7's blew him to pieces.
I guess if I was 1/2 red, I'd be aggressive too.