I woke up, went to check on MKitten (he usually sleeps with me) and found him patting the body of a still warm tiny mouse! 
So I knew MCat had murderous tendencies in the past (including stoats), but MKitten's a Devon Rex, who apparently make friends with a creature rather than kill it! I found a frog in the house a couple months back, but he was just patting it gently. I thought he'd brought it in order to make friends with it. [naive]
Feel guilty for buying him lots of life-like toy mice.
Did I encourage him to kill?