Grass snake, ringed snake
Natrix natrix
Grass snakes are one of the few animals that play dead as a defense against predators.

Statistics
Length: 70-120 cm. Females are larger than the males, and can occasionally reach 200cm in length.

Physical description
Grass snakes are typically grey-green in color, often with black spots and a yellow/cream/orange collar. Their color varies according to distribution, and completely black or partial albino individuals sometimes occur. Black lines run down from their large golden eyes to their top lips. Their underside is usually white or pale yellow with a checkering of blue-black and white markings. Their forked tongues are blue-black.

Distribution
Grass snakes are distributed over much of Europe except for the far north, parts of North Africa and central Asia. Although absent from Scotland and Ireland, they are widespread in England and Wales, but have become increasingly scarce in recent years.

Habitat
They prefer damp habitats, including river banks, ponds and ditches, but they also inhabit hedgerows, woodland margins, farmland and meadows.

Diet
Grass snakes feed on tadpoles, frogs and toads, as well as fish, newts, and occasionally mice and small birds. Most hunting is done underwater, and prey is typically swallowed alive.

Behavior
Grass snakes are active during the day and spend time basking in the sun to warm up. They hibernate from October to March, often communally in old rabbit burrows, wall crevices, in piles of manure or under tree roots. They are good swimmers - their generic name means water snake. They swim with their heads out of the water, but if disturbed, grass snakes will dive underneath and hide amongst water weeds. They can remain underwater for up to an hour. When threatened, grass snakes puff up their bodies and hiss loudly in an attempt to frighten the predator away. If contact is made, they emit a foul-smelling liquid from their anal glands. If this fails to put off an attacker, they roll over on to their backs and play dead. They remain very still with their mouth open and their tongue hanging out for up to 15 minutes, or until the attacker loses interest. Since many carnivores will eat carrion, this seems like a strange method of defense, but it seems to work.

Reproduction
Grass snakes mate in April-May. The male follows the female about until they twist the lower parts of their bodies together and copulate. The female lays 8-40 eggs, depending on her size, in July-August. A clutch usually contains about 10 eggs held together by mucous, secreted by the glands of the oviduct, which then dries to hold the eggs together. Female grass snakes choose a warm site to lay their eggs, such as a compost heap or under rotting logs, and will often use the same egg-laying sites as other females. A communal site may contain over a thousand eggs. The females stay near the nest site for a few days. The young grass snakes have an egg tooth to help them hatch out of the leathery eggs in late August-September.

Conservation status
Grass snakes are protected under the Wildlife and Countryside Act 1981 from being killed, injured or sold. The Sardinian subspecies N.n. cetti is classified as Critically Endangered by the 2000 IUCN Red List.

Notes
Although grass snakes produce a venomous secretion that is toxic to small animals, they are harmless to humans.

Statistics
Length: 50-65cm. Females are larger than the males.

Physical description
Adders are relatively short and robust with large heads and a rounded snout. The red-brown eyes have vertical elliptical, rather then round, pupils - a feature of all venomous snakes. Males are usually a grey or buff color with vivid black markings, although they can also vary from silver to yellow or green in color. Females are brown with dark red-brown markings that are less prominent than in the males. Both sexes have a zigzag pattern running along the back with a / or X-shaped marking at the rear of the head, although this zigzag pattern may be replaced by a straight brown stripe with dark spots on either side. Adders have black undersides. Melanistic (black) individuals sometimes occur in mountainous regions.

Habitat
Adders occupy a variety of habitats, including open woodland, hedgerows, moorland, sand dunes, riverbanks, bogs, heath land and mountains. They prefer undisturbed countryside and can be found in surprisingly wet habitats throughout the summer months.

Diet
Adders use venom to immobilize prey such as lizards, amphibians, nestlings and small mammals. After striking their prey, they will leave the venom to take effect before following the victim's scent to find the body. This is an economical way of hunting, avoiding any damage that could be caused by struggling with prey.

Behavior
Adders are active during the day, spending time basking until their body temperature is high enough to hunt for food. In some of the hotter countries of their range, they may emerge at dawn and dusk to avoid the intense heat. Mating takes place between April and May, with males often fighting for females. They rear up at each other and try to push the head of their opponent onto the ground. Eventually, one male will give up and search for another mate. Adders hibernate from September to March when temperatures dip below nine degrees Celsius, often using deserted rabbit or rodent burrows, or settling under logs. They sometimes hibernate communally. Males emerge 2-5 weeks before the females and shed their skin before setting off in search of females.

Reproduction
Males follow the females around until she allows them to copulate with her. This takes place in April-May. Adders have a 3 to 4 month gestation period and are one of the few snakes that are viviparous (give birth to live young). In late August females give birth to between 5 and 20 live young, although usually the number is between 6 and 10. The young remain close to their mother for a few days, before going off in search of food. Females do not breed on consecutive years, as they do not have time to build up sufficient fat reserves to produce another set of young from one breeding season to the next.

Conservation status
Adders are protected under the Wildlife and Countryside Act 1981 from being killed, injured or sold.