Q: How can snakes climb up trees?
A: Snakes use “concertina locomotion” to climb trees – the act of gripping with some parts of the body while pulling or pushing with other parts of the body in the general direction of movement. Ripples of muscle travel along the snake’s length while the spaces in between
Concertina locomotion is very irregular and appears to be quite strenuous. So, it takes snakes much longer to climb a tree than they could move on the ground or in the water.
This push/pull motion is made possible by scales that are keeled, or ridged. Think of the keel on the bottom of a boat. Unlike smooth scales, keeled scales have raised ridges on the center of each scale which enables the snake to get a grip on rough surfaces, much like a tire with a good tread grips the road better than a bald tire.
Snakes cannot stick to smooth walls the way insects and lizards often do; the snake must have something for the keel to rest on in order to push up. So working in concert with the body muscles, the keeled scales lodged in bark crevices help the snake push against the bark on the tree and inch upward. And yes, sometimes snakes do lose their grip and fall out of a tree.
All snakes either have smooth or keeled scales, and one way to distinguish is that smooth scales typically reflect light, making the color pattern of these snakes shiny, glossy, or iridescent, whereas keeled scales tend to make snakes appear dull and non-reflective because of the raised ridge. Because snakes climb with their bellies to the tree trunk, the scales on their undersides of some snakes may be keeled while the scales on the topside may not be.