My particular rat was about 5 inches long (with a 5 inch-long tail). He loved the Intruder rat trap. For three nights I placed peanut butter in the trap and each time he licked the trap clean -- and never got caught. The first two times the trap sprung shut after-the-fact (perhaps the rat bumped into it while cleaning off his whiskers after his lovely peanut butter meal). The third time the trap didn't even bother to shut. It sat there in the morning, still open, with the peanut butter stolen by my rat. Finally I placed a small bit of peanut butter on a rat-sized glue trap and place the trap against one of my baseboards. Mr. Nibbles was caught in about 3 hours. He is now very much a dead Mr. Nibbles. But don't feel too sorry for him, he enjoyed many lovely peanut butter meals thanks to the Intruder Rodent Restaurant -- I mean Rodent Trap.