New guest in our menagerie

The other day I saw the cat playing with the biggest mouse I've ever seen. The wife and mother-in-law jump straight to "rat" but I swear its not a rat. The wife saw it wandering through the yard today followed by a fairly disinterested catdangling from the cat's mouth and squirming to get out. Apparently it is just not as exciting as a mouse. Our new yard pet? Looks like a gerbil. I suppose the neighbors got rid of theirs.