The rats are common occurences, according to my now ensign. I sent him mouse and rat traps during plebe year. It is my understanding that if a mid catches a live rat/mouse, the rodent is selected for one of the following by the mid: sub school (flush); parachute school (flung out the window of an upper deck Bancroft dorm room. There was a third option as well, which I don't remember.
It breaks my heart to think they hurt animals this way.