I've been noticing some strange behavior in the animals in my fort lately. I'm not terribly experienced in handling animals in Dwarf Fortress so I'm not entirely sure which, if any, of these issues are actually bugs. The two things I want to focus on are ways animals are misbehaving due to doors.
The first strange behavior was encountered when I noticed a lot of animals were running through my woodshop. The way I had built my workshops, I made large rooms dedicated to different types of building. Each of these workshops has several double-doors on its sides, leading to a five-square wide 'main road'. The main road is set to high traffic, so the dwarves all use it for getting around, but the animals don't pay any heed to traffic labels and were walking through the workshop with gleeful abandon, in order to catch up to their various owners. I didn't like this, so I decided to set the doors to the woodshop to 'shut tightly', and not let animals through. There were still some animals in the room, so I left one pair of double-doors pet passable.
To my surprise, the animals did not leave the room. They became confused and started flashing question marks, the way they would if I put them in a room with only blocked exits. Worse yet, as I left it for a while, more and more animals were piling up against the shut door. After a bit, I realized what was going on. The animals were pathfinding through the doors, even though they couldn't pass them, and were unable to take the longer path out of the room, even though it was the only path available. I set all the doors as pet-passable and let them get back to their lives.
I had ignored it at the time, but something else is happening that made me remember this problem. The second strange behavior. I just cleared out the monsters in a cave pool and mined out the area around it to make an indoor park for my dwarves. I walled off a small area in a corner and put a single door sealed tightly against pets. I also set it to restricted traffic, to keep nosy dwarves out. It's a web farm; the idea is to give the cave spiders someplace to do their thing without dwarves crushing the webs, or cats killing them.
While passing by the web farm I noticed something... there was a kitten standing at the door, trying to get at the spiders inside. He could pathfind in to where there were spiders, but couldn't pass the door. This is a really annoying problem, since it means my cats will constantly be standing at the door trying to get in. I figure it's a pathfinding bug in animals... And decided to report it.