First post here, and it's mostly because I've been driven to the brink of insanity by these damned raccoons!
I just don't understand how they are getting in. I've had the fortress sealed so tightly that a HYDRA couldn't get inside without getting caught (I know, cause I've got the bastard in a cage, waiting on my DM to arrive to turn him into an awesome door guard). Yet somehow, not one but TWO raccoons managed to sneak past SIX guard dogs in a straight 3x3 corridor (Restrained against the walls with ropes in pairs), past TWO lines of traps that went wall to wall (One with massive corkscrews, the second with cages), past a stationed squad of 5 armed dwarves, into my clothing stockpile (Which is in the middle of my stockpile room, one of the busiest rooms in my 120 dwarf fortress), steal several exceptional cloth items, and then sneak all the way back out and exit the map, without EVER being seen.
This is not the first time it's happened either. I've checked every last thing I can think of. The only other 'entrances' into my fortress are the flood tunnels for my farms and my well. The flood entrances are blocked with floodgates, and the well goes down 3 z levels before taking a diagonal turn to kill the pressure and hooking back up, all under 7/7 water. What the heck kind of tags do those little buggers have that lets them do that?