Snake

What is a snake?	A snake is a long, legless reptile that can be found on every continent except Antarctica.
How many species?	There are over 3,400 species of snakes in the world.
Where do they live?	Snakes live in forests, deserts, grasslands, and even underwater in some species.
Interesting fact	Some snakes can fly glide through the air using their bodies.

Snakes are long, limbless reptiles that belong to the suborder Serpentes. They are ectothermic, meaning they need the sun or warm places to change their body temperature. Their bodies are covered in overlapping scales. Many snakes have flexible skulls, which help them swallow food bigger than their heads. To fit in their slim bodies, their internal organs are stacked one in front of the other, and most snakes have just one working lung.

Snakes live on every continent except Antarctica. You can find them in forests, deserts, and many other places. There are about thirty families of snakes, with over 4,170 species. They come in many sizes, from the tiny Barbados threadsnake, which is about 10.4 cm long, to the huge reticulated python, which can be nearly 7 meters long. Scientists think snakes came from lizards, maybe during the Jurassic period, a very long time ago.

Most snakes are not venomous. The ones that have venom use it mostly to catch their food, but some venoms can be harmful to people. Snakes that are not venomous usually catch their food by swallowing it whole or by using constriction to hold it still.

Etymology

The word snake comes from Old English snaca, a word that means "to crawl or creep." This idea is also found in other languages, such as Sanskrit. As time passed, snake became the common word we use today. Other older words like adder changed their meanings. The word serpent also has roots meaning "to creep," linking back to very old languages.

Taxonomy

Legless lizards

Main article: Legless lizard

Snakes are reptiles without limbs, but there are lizards that also lack limbs. These lizards look like snakes but are not snakes. Examples include glass snakes and amphisbaenians.

Evolution

The fossil record for snakes is not very complete because their small, delicate skeletons do not turn into fossils easily. The oldest known snake fossils are from the Cretaceous period, about 112 to 94 million years ago. These early snakes often still had hind limbs.

Scientists think snakes came from lizards. Some early snakes, like pythons and boas, have tiny hind limbs, showing that their lizard ancestors had legs. Over time, snakes lost their limbs, perhaps as they adapted to living underground or in water.

Fossils

Fossil evidence suggests snakes may have evolved from lizards that lived underground during the Cretaceous Period. An early fossil snake relative, Najash rionegrina, was a two-legged animal that lived underground. Another important fossil is Tetrapodophis amplectus, a 113-million-year-old fossil that looks like a snake but has four legs. Scientists are still studying whether it was a true snake or another type of lizard.

Genetic basis of snake evolution

Main article: Limb development

Studies show that the loss of limbs in snakes is linked to DNA changes in a part of the sonic hedgehog gene, which helps with limb development. More advanced snakes have no signs of limbs, but some, like pythons and boas, still have small, leftover hind limbs. Even python embryos start with fully developed hind limb buds, but these stop growing because of the DNA changes.

Family	Taxon author	Genera	Species	Common name	Geographic range
Infraorder Alethinophidia 25 families
Acrochordidae	Bonaparte, 1831	1	3	Wart snakes	Western India and Sri Lanka through tropical Southeast Asia to the Philippines, south through the Indonesian/Malaysian island group to Timor, east through New Guinea to the northern coast of Australia to Mussau Island, the Bismarck Archipelago and Guadalcanal Island in the Solomon Islands.
Aniliidae	Stejneger, 1907	1	1	False coral snake	Tropical South America.
Anomochilidae	Cundall, Wallach, 1993	1	3	Dwarf pipe snakes	West Malaysia and on the Indonesian island of Sumatra.
Atractaspididae	Günther, 1858	12	72	Burrowing asps	Africa and the Middle East
Boidae	Gray, 1825	14	61	Boas	Northern, Central and South America, the Caribbean, southeastern Europe and Asia Minor, Northern, Central and East Africa, Madagascar and Reunion Island, the Arabian Peninsula, Central and southwestern Asia, India and Sri Lanka, the Moluccas and New Guinea through to Melanesia and Samoa.
Bolyeriidae	Hoffstetter, 1946	2	2	Splitjaw snakes	Mauritius.
Colubridae	Oppel, 1811	258	2055	Typical snakes	Widespread on all continents, except Antarctica.
Cyclocoridae	Weinell & Brown, 2017	5	8	Cyclocorids	The Philippines
Cylindrophiidae	Fitzinger, 1843	1	14	Asian pipe snakes	Sri Lanka east through Myanmar, Thailand, Cambodia, Vietnam and the Malay Archipelago to as far east as Aru Islands off the southwestern coast of New Guinea. Also found in southern China (Fujian, Hong Kong and on Hainan Island) and in Laos.
Elapidae	Boie, 1827	55	389	Elapids	On land, worldwide in tropical and subtropical regions, except in Europe. Sea snakes occur in the Indian Ocean and the Pacific.
Homalopsidae	Bonaparte, 1845	28	53	Homalopsids	Southeastern Asia and northern Australia.
Lamprophiidae	Fitzinger, 1843	16	89	Lamprophiids (formerly included Atracaspididae, Psammophiidae, and several other families)	Africa (including the Seychelles)
Loxocemidae	Cope, 1861	1	1	Mexican burrowing snake	Along the Pacific versant from Mexico south to Costa Rica.
Micrelapidae	Das et al., 2023	1	4	Two-headed snakes	Eastern Africa and the Levant
Pareidae	Romer, 1956	3	20	Snail-eating snakes	Southeast Asia and islands on the Sunda Shelf (Sumatra, Borneo, Java, and their surrounding smaller islands).
Prosymnidae	Kelly, Barker, Villet & Broadley, 2009	1	16	Shovel-snout snakes	Subsaharan Africa
Psammodynastidae	Das et al., 2024	1	2	Mock vipers	Tropical Asia
Psammophiidae	Bourgeois, 1968	8	55	Psammophiids	Africa (including Madagascar), Asia and southern Europe
Pseudaspididae	Cope, 1893	2	2	Pseudaspidids	Subsaharan Africa
Pseudoxyrhophiidae	Dowling, 1975	22	89	Pseudoxyrhophiids	Mostly Madagascar and the Comoros; 5 species in subsaharan Africa, 1 in Socotra
Pythonidae	Fitzinger, 1826	8	40	Pythons	Subsaharan Africa, India, Myanmar, southern China, Southeast Asia and from the Philippines southeast through Indonesia to New Guinea and Australia.
Tropidophiidae	Brongersma, 1951	2	34	Dwarf boas	West Indies; also Panama and northwestern South America, as well as in northwestern and southeastern Brazil.
Uropeltidae	Müller, 1832	8	55	Shield-tailed snakes	Southern India and Sri Lanka.
Viperidae	Oppel, 1811	35	341	Vipers	The Americas, Africa, and Eurasia east to Wallace's Line.
Xenodermidae	Cope, 1900	6	18	Dragon and odd-scaled snakes	East Asia, Southern and southeastern Asia, and islands on the Sunda Shelf (Sumatra, Borneo, Java, and their surrounding smaller islands).
Xenopeltidae	Bonaparte, 1845	1	2	Sunbeam snakes	Southeast Asia from the Andaman and Nicobar Islands, east through Myanmar to southern China, Thailand, Laos, Cambodia, Vietnam, the Malay Peninsula and the East Indies to Sulawesi, as well as the Philippines.
Xenophidiidae	Wallach & Günther, 1998	1	2	Spine-jawed snakes	Borneo and peninsular Malaysia.

Family	Taxon author	Genera	Species	Common name	Geographic range
Infraorder Scolecophidia 5 families
Anomalepidae	Taylor, 1939	4	18	Primitive blind snakes	From southern Central America to northwestern South America. Disjunct populations in northeastern and southeastern South America.
Gerrhopilidae	Vidal, Wynn, Donnellan and Hedges 2010	2	18	Indo-Malayan blindsnakes	Southern and southeastern Asia, including Sri Lanka, the Philippines, and New Guinea.
Leptotyphlopidae	Stejneger, 1892	13	139	Slender blind snakes	Africa, western Asia from Turkey to northwestern India, on Socotra Island, from the southwestern United States south through Mexico and Central to South America, though not in the high Andes. In Pacific South America they occur as far south as southern coastal Peru, and on the Atlantic side as far as Uruguay and Argentina. In the Caribbean they are found on the Bahamas, Hispaniola and the Lesser Antilles.
Typhlopidae	Merrem, 1820	18	266	Typical blind snakes	Most tropical and many subtropical regions around the world, particularly in Africa, Madagascar, Asia, islands in the Pacific, tropical America and in southeastern Europe.
Xenotyphlopidae	Vidal, Vences, Branch and Hedges 2010	1	1	Round-nosed blindsnake	Northern Madagascar.

Distribution

Approximate world distribution of snakes

There are about 3,900 kinds of snakes. They live nearly everywhere except Antarctica. They can be found as far north as Scandinavia and as far south as Australia. Snakes live on land, in water, and even as high as 16,000 feet in the Himalayan Mountains.

Some islands, like Ireland, Iceland, and New Zealand, don’t have snakes. But New Zealand’s northern waters are sometimes visited by the yellow-bellied sea snake and the banded sea krait.

Biology

Snakes are long, limbless reptiles known for swallowing prey bigger than their heads. They are covered in overlapping scales and cannot control their own body temperature, so they rely on the environment to stay warm or cool.

Snakes have special ways to sense the world. Some, like pit vipers, have pits that sense heat to find prey. They use their forked tongues to pick up scent particles, which they analyze to find food or danger. Most snakes can feel vibrations to detect sounds around them. Vision varies, but many can track movement well.

The skin of a snake is covered in dry, smooth scales that protect them and help them move easily. These scales are made of keratin and are shed in a process called molting. Snakes have flexible skulls, which helps them swallow large prey. Their bodies have a skull, hyoid bone, spine, and ribs, with some small remains of hind limbs. Inside, snakes have a three-chambered heart and one functional lung, which suits their long, slender shape well. Some snakes, like cobras and vipers, use venom from fangs to catch prey or defend themselves.

Behavior and life history

Snakes have special ways to survive and find food. In cold places, snakes enter a resting state called brumation. During brumation, snakes stay awake but do not move much. They rest in places like burrows or under rocks.

All snakes eat meat. They hunt small animals such as lizards, frogs, birds, and even other snakes. Snakes are ambush predators, meaning they wait for the right moment to catch their food. They swallow their prey whole because they cannot bite or tear food into pieces. Their jaws are very flexible, allowing them to open wide to eat animals larger than their heads. Some snakes use venom to help with their food, while others wrap around their prey to hold it tight. After eating, snakes rest to digest their food, which can take a long time.

Interactions with humans

Snakes usually stay away from people and won't attack unless they feel scared or hurt. Most snakes, especially those that aren't venomous, are not dangerous to people. A bite from a non-venomous snake might hurt a little but is usually not serious. Venomous snakes are more dangerous, and their bites can be very serious.

In some places, people used to have shows with snakes, called snake charming. These shows happen less now because of rules to protect animals and new types of entertainment. Some people catch snakes to take away venom for making medicine, then let the snakes go. In many cultures, eating snake meat is popular, and snakes are also kept as pets in some countries. Snakes have been part of stories and symbols for thousands of years, standing for different ideas in many cultures and religions.