A cat will work for Mice, but not for a rat.. Rats have been known to kill and eat the cat. A 3 pound cat is out classed by a 10 pound+ rat on the rats worst day. Snakes love rats...the bigger the rats get the bigger the snake grows to eat them. I have though "shot" 15 to 20 pound rats on Docks and wharfs in the pacific. 
the cat in the pic above is at least 15 pounds, and ive seen him kill grown possums, he's a true hunter
unfortunately i haven't seen the old boy in 3 days
