Rat poison does NOT kill that fast generally it is made from warferine (spell?) or similar which thins the rat's blood so when it knocks itself (as rats frequently do) they bleed internally and suffer an agonising death!!!
I know this cos I had rats in my attic a few years ago and the rat lady that came to get rid of them told me (I sorta thought I wouldnt mind living with them after hearing that!!)...all 4 of the houses on my side of the close got them... I got them cos my semi was joined to next door whose garage was joined to their next doors garage they got into the garage and into the loft thus into my loft!
BTW the poison only got a few and the rest vacated or side of the close and went over to the other side
