I pit people using rat poison unnecessarily. (Mercy killing of mouse)

I googled the active ingredient Bromadiolone (I got the ingredient by going to your link). It’s just a potent anticoagulant, so the critter dies from internal bleeding. I wouldn’t call that mummification.

ETA - Your link itself also says it’s an anticoagulant (just glanced at it the first time before googling).

(tried to “nm” my last message but didn’t do it in time - I see I have been well ninja’ed AND it is a zombie - sorry!)