I guess a large rat would be okay to?
LOL! If you haven't read "King Rat" by James Clavell, you should.
Actually, in my opinion, it's one of those books that should be required reading in high school.
As a side note, Clavell was indeed a prisoner in Changi, Singapore during WWII, and the hidden radio described in the book really existed. It's on display in the Imperial War Museum in London. I've seen it.