Yesterday I watched a beautifully colored Garter Snake about 20" in length and the width of my middle finger squirm his way across a palm branch until he lost his friction with the dried leaf and fell to the forest floor 15 feet below. The fall didn't kill him, just knocked him upside down. He writhed upright and began a quirky-jerky circle looking for the culprit that had pulled the proverbial rug out from under him (maybe it could also have been checking for predators). Then he nonchalantly squirmed away. Guess you could say he is "alergic to gravity."