In our second house we heard a lot of noises coming from our fireplace one week. Now this was a huge old house and the fireplace was sized the same way. The opening was 4 feet across and 3 feet high. You could actually stand up in the firepit since the flue was about 2' X 4'. After a few days we saw the culprits - a whole family of racoons were living right on the flue damper. Not wanting to take any chances we called the exterminator who managed to remove 4 babies. The mother was another matter - she didn't want to leave. He finally managed to smoke her out and she tried to jump back into the large tree that overlooked the house. Well she slipped off the branch and fell the 3 stories to the ground. Boy what a splat! Fortunately she shook it off and ran away along with her babies to a new home. The exterminator put a screen over the chimeny opening and no more racoons.