Can you climb a tree?
Can you climb a tree without branches to grasp?
Now imagine climbing a tree without the benefit of hands or feet!
I found this 5-ish foot rat snake easing up a white oak. Notice how it bends to find any slight protrusion in the rough bark. By pressing against many points of contact, it distributes its weight and supports itself as it inches up the trunk. It isn’t a fast process, but snakes are patient. Besides bark, I’ve seen snakes on brick walls as well.
That explains the how, but what about the why? For the same reason a snake does most things – the quest for food. The serpent searches for nests, consuming bird eggs or young squirrels. Snakes may also hide in trees to escape their own predators. Wetland snakes such as cottonmouths often bask in the branches of trees, plopping back into the water when startled.
The red-cockaded woodpecker has developed an impressive defense to deter slithery predators. These birds make their nests in cavities they excavate in longleaf pines. The woodpeckers smooth the rough bark on the nest trees as well as surrounding pines. They also excavate small holes (“resin wells”) above, around, and below the nest cavity. Resin flows from these wells, forming a smooth coating on the tree truck that snakes find difficult to cross.