Snakes have no legs, and they have no outside ears. Snakes have no eyelids, so they cannot blink, and instead of eyelids, a snake has a clear scale over each eye, called a spectacle or eye cap, that protects it. A snake's body is covered with scales, and its scales are made of keratin, the same material as human fingernails. Snakes shed their old skin as they grow, and they shed it in one piece.

Snakes live on every continent except Antarctica, and they live in many kinds of places: sidewinders in sandy deserts, and king cobras in rain forests and plains. Green anacondas live in South America, in rivers and swamps, and anacondas spend most of their time in the water. Some snakes live up in trees, and blind snakes, or threadsnakes, live underground and eat ants and termites. A wild snake is best left alone: it will usually go its own way. If one is near a home, a grown-up can call animal control.

The most common way snakes move is serpentine movement: the snake bends its body in a series of curves and pushes against surfaces. In concertina movement a snake coils its body into alternating curves, then straightens out to push itself forward, and in rectilinear movement a snake moves forward in a straight line, flexing the skin of its belly. Wide, flat scales on a snake's belly grip the ground like the treads of a tire, which helps the snake move. In sidewinding, a snake bends in waves both side to side and up and down, and sidewinder rattlesnakes are experts at it. Georgia Tech scientists studied desert sidewinder rattlesnakes climbing sand dunes and built a snake-like robot that could climb nearly any hill.

A snake's sharpest sense is smell. Jacobson's organs are two small organs in the roof of a snake's mouth, and each opens to the mouth through a tiny hole in the palate. A snake flicks its forked tongue to pick up chemicals from the air, the ground or the water. After a flick, the tongue goes back into its mouth and fits into the Jacobson's organ, which sends signals to the same part of the brain as the nose. A snake's two tongue tips each deliver chemicals to their own Jacobson's organ, so the brain can compare the two sides, as your two ears let you tell where a sound comes from.

A snake senses moving prey by feeling vibrations, which it picks up through its jawbones and body. Snakes can detect vibrations between 50 and 1,000 hertz, while people hear between 20 and 20,000 hertz, so a snake senses a much narrower range of vibrations than we hear. Some snakes have heat-sensing pits on the sides of the head that sense the warmth given off by warm-blooded prey. A snake's pit organ, which sits between the eye and the nostril in rattlesnakes, can sense infrared radiation, which is heat. The pit gives the snake a picture of its surroundings made from infrared radiation, a thermal image.

Many snakes are ambush hunters. They hide and wait for an animal to come close, instead of chasing it. A boa constrictor squeezes its prey until the heart stops pumping blood. It does not kill by suffocating the prey. Some snakes, called constrictors, catch food by wrapping their body coils around an animal and squeezing. Boa constrictors eat birds, lizards, rats, squirrels, bats and other small to medium animals, and rattlesnakes eat small animals such as mice, rats, squirrels, rabbits and lizards. Garter snakes eat small animals such as earthworms, slugs and insects, and eastern coral snakes mostly eat other reptiles and amphibians, such as lizards, frogs and smaller snakes.

Snakes eat other animals, and depending on the snake, the food can be mice, rats, rabbits, fish, frogs or even other snakes. The king cobra feeds mainly on other snakes. Snakes do not chew their food. They swallow their prey whole, and a snake's mouth bones are loosely attached to each other and to the skull, and teeth that face inward trap prey once it is in the mouth. Together these let a snake swallow animals bigger than its head. After a big meal a snake does not need to eat again for a long time, and Burmese pythons can go four to six weeks between meals.

Five kinds of snakes can glide through the air from tree to tree, in southern and southeast Asia. A flying snake flattens its body by spreading its ribs, which makes a shape that catches the air. As of June 2020, Virginia Tech researchers described how a paradise tree snake begins a glide by curving into a J-shaped loop and springing up and out. It then flattens its body everywhere but the tail, so the body works like a morphing wing that makes lift and drag as air flows over it, while waves run down its length. Paradise flying snakes launched from a tower typically landed about 10 meters away, and one glided as far as 21 meters.

Words to know

• serpentine: curvy, snaking
• concertina: folding, accordion-like
• rectilinear: straight-line
• infrared: heat energy
• ambush: hidden attack