Snakes have no legs. Scientists think snakes evolved from lizards more than 100 million years ago, though the fossil record is thin. As of November 2019, a study of the fossil snake Najash found that legged snakes living nearly 100 million years ago still had a cheekbone, the jugal. This bone has almost vanished in modern snakes. As of November 2019, the team also concluded that snakes kept small hind legs for the first 70 million years of their history. As of August 2016, Bangor University researchers changed the Oct4 gene in mouse embryos, and the mice grew more trunk vertebrae, which supports the idea that a change in when Oct4 turns on and off helped make snakes' long trunks.

Snakes eat other animals. Many snakes are ambush hunters. They hide and wait for an animal to come close, instead of chasing it. Snakes do not chew their food. They swallow their prey whole. A snake's mouth bones are loosely attached to each other and to the skull. 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. 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.

In rectilinear movement a snake moves forward in a straight line, flexing the skin of its belly. In concertina movement a snake coils its body into alternating curves, then straightens out to push itself forward. In sidewinding, a snake bends in waves both side to side and up and down. As of October 2014, Georgia Tech researchers measured that sidewinder rattlesnakes climbing sandy slopes do not dig deeper as the slope steepens, and instead put more of their body on the sand at each moment, which lowers the chance of slipping.

Five kinds of snakes can glide through the air from tree to tree, in southern and southeast Asia. Flying snakes are tree snakes of tropical forests. A flying snake flattens its body by spreading its ribs, which makes a shape that catches the air. As of June 2020, a Virginia Tech study filmed more than 100 glides of paradise tree snakes and built a 3D model, and showed that flying snakes ripple as they glide: with the ripples switched off in the model, the snake tumbled, and with them on, its body stayed steady and glided farther.

As of November 2026, the green anaconda is the heaviest snake, weighing up to about 550 pounds (250 kg). As of November 2026, the reticulated python is the longest snake species in the world today. As of November 2026, the longest wild snake measured with proof is a reticulated python called the Baroness, found in Indonesia in December 2025 and measured at 23 feet 8 inches (7.22 m) in January 2026.

Words to know

• fossil: ancient remains
• jugal: cheekbone
• gene: body instruction
• vertebrae: backbone pieces