Snake

A snake is a reptile belonging to the order Serpentes. It is characterized by a long, slender body, the absence of limbs, and scales (small plates covering the skin). Snakes evolved from lizards with limbs, which were lost over a long period of biological development.

Every species of snake is carnivorous. They consume live animals that they swallow whole, such as rodents, birds, frogs, insects, and sometimes other snakes. Because they lack legs to run with, snakes move across the ground by contracting their body muscles and using their ventral scales.

Skeletal structure

The spine consists of many distinct vertebrae, providing great flexibility. Internal organs are elongated and arranged in sequence; in many species one lung is functional while the other is reduced or absent. Snakes lack an external ear; they sense ground vibrations instead. They have no eyelids; instead, a transparent scale covers the eye and is shed along with the rest of the outer skin.

Sensing and hunting

Snakes extend the tips of their forked tongue outside the mouth to collect particles from the air, then draw it back into a specialized organ in the roof of the mouth that combines taste and smell. Some species, such as pit vipers, have heat-sensing pits that allow them to detect warm-blooded prey in darkness. Snakes use two main hunting methods: ambush, or active pursuit until the prey stops breathing.

Venom and effects on humans

Most snake species are venomous, but some—including cobras, vipers, and mambas—have fangs that deliver venom. Venom affects either the nervous system or the blood, depending on the species. Snake bites are a significant public health concern in many countries in Africa, Asia, and Latin America; the primary treatment is antivenom. Snake venom is also studied for medical research.

Habitat and ecological role

Snakes inhabit all continents except Antarctica and also occur in warm seas. They live in forests, mountains, deserts, and freshwater environments. Many species lay eggs, while others give birth to live young. They play a role in their ecosystems by controlling populations of rodents and small animals.