To me, a slow death is horrible. But I've also seen what happens to mice with rat poison.. basically they bleed to death all over the place. It's horrific, plus if a predator finds the carcass, they can die the same death because they're eating the poison too. If you have to kill something, do it fast. Mouse trap, shoe, whatever. That's why I try to take bugs away from the cats if they're not killing it fast enough. I hate seeing the cats deleg a poor spider and then bat it around while it's alive. I usually get a piece of papertowel & squish it and then give the kitty a pompom to torture.
