This is not a pleasant story. Sometime in the 1960s, a hunting dog shimmied up a hollow space inside a tree, presumably after some smaller animal, and when the hollow narrowed, got stuck. There was no rescue. The poor dog died of thirst, alone in the dark, and then its body was mummified by tannins in the wood, and remained there for decades until the tree was cut down. And there he was.
Now its on display in a museum, which is rather grim. I hope none of you are claustrophobes, because this would give me the heebie-jeebies.