Fifty years ago a dog went up a tree chasing a racoon or something. He never came down.
Fast forward twenty years. A group of loggers cut down a chestnut oak somewhere in a forest in the state of Georgia, the United States of America. When they sawed off the trunk, they discovered the mummified corpse of a dog entombed inside. Apparently, the dog had chased his prey down a hollow in the tree where it became stuck and then died of starvation. Dry conditions inside the hollow of the tree allowed the corpse to dry without rotting. The upward draft of air apparently carried the scent of the dead animal away, so it wasn't devoured by insects or other creatures. The tannic acid of the oak, which is a natural desiccant, also helped absorb the moisture and hardened the animal's skin.
Photo credit: Scott Beahan/The Newsweek