I used to have a terrible problem with cat poo, then I got sweep and after the first year I've never seen any since. They don't tend to hang around in the garden anymore as he likes to chase them. They get a,fair head start as he barks his head off first and I've made sure there's plenty of places for them to get out where he can't follow. He caught up with a hare once, the hare sat down, then so did sweep. I think the cats are safe! Didn't know about snakes but it could be true, we do get them in the garden too.