Grass Snake
Overview
 
The grass snake sometimes called the ringed snake or water snake is a Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

an non-venomous snake
Snake
Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...

. It is often found near water and feeds almost exclusively on amphibians.
The name natrix is probably derived from the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 nare or natare "to swim".
The grass snake is typically dark green or brown in colour with a characteristic yellow collar behind the head, which explains the alternative name ringed snake.
Encyclopedia
The grass snake sometimes called the ringed snake or water snake is a Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

an non-venomous snake
Snake
Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...

. It is often found near water and feeds almost exclusively on amphibians.

Etymology

The name natrix is probably derived from the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 nare or natare "to swim".

Description

The grass snake is typically dark green or brown in colour with a characteristic yellow collar behind the head, which explains the alternative name ringed snake. The colour may also range from grey to black, with darker colours being more prevalent in colder regions, presumably owing to the thermal benefits of being dark in colour. The underside is whitish with irregular blocks of black, which are useful in recognizing individuals. In Great Britain
Great Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...

 the grass snake is the largest reptile, reaching up to 190 centimetre total length, though such large specimens are rare. Females are considerably larger than males, typically reaching a size of 90 centimetre when fully grown. Males are approximately 20 centimetres (7.9 in) shorter and significantly smaller in girth. Weight is about 240 grams (8.5 oz).
Since the colour of its collar is often pale yellow to white in the Balkans region, the name for this snake in Serbian/Croatian language is belouška/bjelouška, which means white eared snake.

Distribution

This species is one of only three snakes to occur in Great Britain
Great Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...

, and is distributed throughout lowland areas of England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

 and Wales
Wales
Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...

; it is almost absent from Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

 and is not found in Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...

, which has no native snakes. It is widely distributed in mainland Europe, ranging from mid Scandinavia
Scandinavia
Scandinavia is a cultural, historical and ethno-linguistic region in northern Europe that includes the three kingdoms of Denmark, Norway and Sweden, characterized by their common ethno-cultural heritage and language. Modern Norway and Sweden proper are situated on the Scandinavian Peninsula,...

 to southern Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

. It is also found in northwestern Africa. British grass snakes belong to the subspecies N. n. helvetica, but experts differ on the number of subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...

.

Feeding

They prey almost entirely on amphibians, especially the common toad
Common Toad
The common toad or European toad is an amphibian widespread throughout Europe, with the exception of Iceland, Ireland and some Mediterranean islands...

 and the common frog
Common Frog
The Common Frog, Rana temporaria also known as the European Common Frog or European Common Brown Frog is found throughout much of Europe as far north as well north of the Arctic Circle in Scandinavia and as far east as the Urals, except for most of Iberia, southern Italy, and the southern Balkans...

, although they may also occasionally eat mammals and fish. Captive snakes have been observed taking earthworms offered by hand, but dead prey items are never taken. The snake will search actively for prey, often on the edges of water, using sight and sense of smell (using the Jacobson's organ
Vomeronasal organ
The vomeronasal organ , or Jacobson's organ, is an auxiliary olfactory sense organ that is found in many animals. It was discovered by Frederik Ruysch and later by Ludwig Jacobson in 1813....

). They consume prey live without using constriction.

Habitat

Grass snakes are strong swimmers and may be found close to fresh water, although there is evidence that individual snakes often do not make use of water bodies throughout the entire season.

The preferred habitat appears to be open woodland and "edge" habitat such as field margins and woodland borders as these may offer adequate refuge while still affording ample opportunity for thermoregulation
Thermoregulation
Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different...

 through basking. Pond edges are also favoured and the relatively high chance of observing this secretive species in such areas may account for their perceived association with ponds and water.

Grass snakes, as with most reptiles, are at the mercy of the thermal environment and need to overwinter in areas which are not subject to freezing. Thus they typically spend the winter underground where the temperature is relatively stable.

Reproduction

As spring approaches, the males emerge first and spend much of the day basking in an effort to raise body temperature and thereby metabolism. This may be a tactic to maximise sperm production as the males mate with the females as soon as they emerge up to 2 weeks later in April or earlier if environmental temperatures are favourable. The leathery-skinned eggs are laid in batches of 8–40 in June to July and hatch after about 10 weeks. To survive and hatch the eggs require a temperature of at least 21 °C (69.8 °F), but preferably 28 °C (82.4 °F), with high humidity. Rotting vegetation
Vegetation
Vegetation is a general term for the plant life of a region; it refers to the ground cover provided by plants. It is a general term, without specific reference to particular taxa, life forms, structure, spatial extent, or any other specific botanical or geographic characteristics. It is broader...

 such as compost
Compost
Compost is organic matter that has been decomposed and recycled as a fertilizer and soil amendment. Compost is a key ingredient in organic farming. At its most essential, the process of composting requires simply piling up waste outdoors and waiting for the materials to break down from anywhere...

 heaps are preferred locations. The young are about 18 centimetres (7 in) long when they hatch and are immediately independent.

Migration

After breeding in summer, snakes tend to hunt and may range widely during this time, moving up to several hundred metres in a day. Prey items tend to be large compared to the size of the snake and this impairs the movement ability of the snake. Snakes which have recently eaten rarely move any significant distance and will stay in one location, basking to optimize their body temperature until the prey item has been digested. Individual snakes may only need two or three significant prey items throughout an entire season.

Ecdysis (moulting)

Ecdysis
Ecdysis
Ecdysis is the moulting of the cuticula in many invertebrates. This process of moulting is the defining feature of the clade Ecdysozoa, comprising the arthropods, nematodes, velvet worms, horsehair worms, rotifers, tardigrades and Cephalorhyncha...

 occurs at least once during the active season. As the outer skin wears and the snake grows, the skin loosens from the body, including from the eyes, which may turn a milky white colour at this time. This presumably affects the eyesight of the snake and they do not move or hunt during this time. The outer skin is eventually sloughed in one piece (inside-out) and normal movement activity is resumed.

Defence

Not being venomous, the snake's only defence is to produce a garlic
Garlic
Allium sativum, commonly known as garlic, is a species in the onion genus, Allium. Its close relatives include the onion, shallot, leek, chive, and rakkyo. Dating back over 6,000 years, garlic is native to central Asia, and has long been a staple in the Mediterranean region, as well as a frequent...

-smelling fluid from the anal glands, or to feign death (thanatosis) by becoming completely limp. They may also perform an aggressive display in defence, hissing and striking without actually opening the mouth. They rarely bite in defence. They may also secrete blood (autohaemorrhage) from the mouth and nose whilst playing dead.

Protection and threats

The species has various predator species, including corvids, stork
Stork
Storks are large, long-legged, long-necked wading birds with long, stout bills. They belong to the family Ciconiidae. They are the only family in the biological order Ciconiiformes, which was once much larger and held a number of families....

s, owls
OWLS
OWLS is a mnemonic used by general aviation airplane pilots to assess an unprepared surface for a precautionary landing.Like all mnemonics this check has become part of aviation culture and folklore.OWLS:* Obstacles* Wind direction...

 and perhaps other birds of prey, foxes and the domestic cat
Cat
The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...

. In England, grass snakes are protected under the Wildlife and Countryside Act 1981 and cannot be harmed or traded without a licence, although they may legally be captured and kept in captivity.

Two of the subspecies are considered critically endangered: N. n. cetti (Sardinian grass snake) and N. n. schweizeri. In 2007, the grass snake was included on the updated UK Biodiversity Action Plan
Biodiversity Action Plan
A Biodiversity Action Plan is an internationally recognized program addressing threatened species and habitats and is designed to protect and restore biological systems. The original impetus for these plans derives from the 1992 Convention on Biological Diversity...

as a species in need of conservation and greater protection.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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