A snake is a reptile, and like all reptiles, snakes are ectothermic, or cold blooded, and covered in scales. They are distinguished from legless lizards by their lack of eyelids, limbs, and external ears. The 2,900 species of snakes spread across every continent except Antarctica and range in size from the tiny, 4-inch-long thread snake, to pythons and anacondas over 23 feet long.
Venomous snakes comprise a minority of the species of snakes. A snake's venom is primarily for killing and subduing prey rather than for self-defense.
All snakes are carnivorous. They eat small animals including lizards, other snakes, small mammals, birds, eggs, fish, snails or insects. They use smell to track their prey, and are very sensitive to vibration, thus a snake is able to sense other animals approaching through detecting faint vibrations in the air and on the ground.
Snakes do not bite or tear their food to pieces. Instead they swallow their prey whole. The body size of a snake influences its eating habits. Smaller snakes eat smaller prey, adult pythons, on the other hand, are able to eat small deer or antelope.
The snake's jaw is the most unique jaw in the animal kingdom. It behaves like a hinge, opening up to 180°. A snake's chin, which is detached in the middle, spreads apart to accommodate its prey.
Once they have eaten, snakes become torpid while the process of digestion takes place. Digestion is an intense activity for snakes, and requires a large amount of metabolic energy. Due to this heightened state of digestion, if a snake is disturbed after recently eating, it will often regurgitate its prey in order to have the ability to escape the perceived threat. When undisturbed, the digestive process is highly efficient, dissolving and absorbing everything but hair, teeth, and claws.
The skin of a snake is covered in scales and has a smooth, dry texture. Most snakes use specialized belly scales to travel and grip surfaces. A snake's eyes are covered by transparent "spectacle" scales.
The shedding of scales is called moulting or sloughing. Snake scales are extensions of their skin. They are not shed separately, but are removed as one complete outer layer of skin during each moult, much like a sock being turned inside out.
Moulting is repeated periodically throughout a snake's life and serves two major functions for snakes: the old and worn skin is replaced, and it helps get rid of parasites such as mites and ticks.
