Because snakes have a flexible lower jaw, they can open their mouths very wide and swallow prey that is wider than they are. Their skin also offers the needed elasticity for the prey to fit in. After a big meal, a snake moves very slowly, so that the prey can be digested. Digestion needs so much energy that some snakes, like the Mexican rattlesnake, increase their temperature by 14 Â°C (57 Â°F). Once digestion is complete, a snake excretes the hair and claws of its prey.Note: Snakes cannot digest plants.