When I was in Costa Rica ('84) I climbed a tree to pet one on the head. He was hanging upside down, as usual. I watched him take 30 minutes to travel the length of a branch - about 6 feet - because he stopped 6 times to take a nap. I knew that if I stayed away from his front paw moving in the direction of his tail I would be safe because that's the only motion he can do quickly. I wasn't prepared for the snarl he gave me though. Kinda scary!!