Grass snake (Natrix natrix)

Also known as: Ringed snake
  
French: Couleuvre à collier
Spanish: Culebra de Collar
KingdomAnimalia
PhylumChordata
ClassReptilia
OrderSquamata
FamilyColubridae
GenusNatrix (1)
SizeAverage female length: 75 - 80 cm (2)
Average male length: 65 cm (2)

The grass snake is classified as Least Concern (LC) on the IUCN Red List (7), is protected in the UK by Schedule 5 of the Wildlife and Countryside Act, 1981 (3), and is listed under Appendix III of the Bern Convention (5).

The grass snake (Natrix natrix) is Britain's largest terrestrial reptile. This snake is typically olive-green, brown or greyish in colour, with a variable row of black bars along the sides, occasionally with smaller round markings along the back in double rows. The underside of the grass snake is off-white or yellowish with dark triangular or rectangular markings. A characteristic black and yellow collar is present behind the head, which has earned the species the alternative name of 'ringed snake' (2). Totally black (melanistic) forms and albinos occasionally arise. Male and female grass snakes are generally similar in appearance, although females are often larger; males can be identified by the presence of a swelling at the base of the tail and by the fact that they have longer tails relative to females (2).

The grass snake is found in lowland areas of Britain. It is widespread and common in some areas of the south and south east of England, is absent from Scotland and becomes rare in central Wales (2). It is absent from Ireland, where it is said to have been expelled by Saint Patrick (4). Elsewhere, the grass snake has a wide distribution in continental Europe, from southern Scandinavia to southern Italy, reaching as far east as Lake Baikal. It also occurs in northwestern Africa. Experts currently disagree as to the number of subspecies of the grass snake; British grass snakes belong to the western subspecies Natrix natrix helvetica (2).

Like all members of the genus Natrix, the grass snake is an aquatic species that is usually closely associated with water (4). It is found in habitats featuring ponds, lakes, streams, marshes and ditches, which provide access to sunshine for basking and plenty of shelter. The grass snake may also be found in open woodland, rough grassland, wet heathlands, gardens, parks and hedgerows (2).

The grass snake is extremely difficult to observe as it is a fast-moving and wary species (2). Because it derives its body warmth from the environment, the grass snake has to bask in the sun after emerging in the morning in order to reach high enough body temperatures to be able to function efficiently and digest its prey (3). During winter, temperatures are too low, and the grass snake will find frost-free places such as deep leaf litter or rock piles in which to hibernate between October and March or April (2).

Courtship and mating takes place from March to June. The male grass snake will curl its body around a receptive female, rubbing the female with his head and wrapping his tail closely around the females body to allow copulation to take place. The female then departs and searches for a nesting site (2). The grass snake is Britain's only egg laying snake (3); eggs are laid in compost or manure heaps where the rotting vegetation creates warm conditions (2). Development of the leathery white eggs depends on the temperature, but hatching usually occurs six to eight weeks after egg-laying. The hatchling snakes escape from the eggs by chipping at the shell with an egg tooth, which is lost shortly after hatching. The male grass snake becomes mature at 3 years of age, but females do not begin to breed until they reach their fourth or fifth year. After reaching maturity, males shed their skin twice a year, whereas females slough their skin once a year just before egg-laying. The grass snake can live for up to 15 years (2). 

The grass snake is an active predator of frogs, toads and newts, although fish, small mammals and young birds may also be taken. Prey is grabbed, then swallowed alive. This species is a good swimmer, and is able to stay submerged for over half an hour (2). The grass snake is predated upon by badgers, foxes, domestic cats, hedgehogs and a number of birds. Relying on wariness for protection, the grass snake often 'plays dead' when threatened, which may dissuade certain predators from killing it. When caught, the grass snake hisses loudly, releases pungent and foul-smelling substances from the anal gland, and will frequently strike with the head, although it does not bite (2).

The grass snake is a much maligned species, and is often an unwelcome visitor to gardens. In some habitats, basking and egg-laying sites have been reduced in numbers (5).

The grass snake is fully protected against being sold, injured or killed in the UK under the Wildlife and Countryside Act 1981 (3). One main aim of the conservation strategy for this species is to educate people about the grass snake, and to encourage them to tolerate its presence (6).

For more on this species and other British reptiles and amphibians see:

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk

  1. National Biodiversity Network Species Dictionary (March 2003):

    http://www.nhm.ac.uk/nbn/
  2. Beebee, T. & Griffiths, R. (2000) Amphibians and reptiles: a natural history of the British herpetofauna. Harper Collins Publishers Ltd., London.
  3. Amphibian and Reptile Conservation Trust (December, 2010)
    http://www.arc-trust.org/animals/grass_snake.php
  4. Staffordshire Biodiversity Action Plan (March 2003)
    http://www.sbap.org.uk/actionplan/species/index.php?id=34
  5. Buczacki, S. (2002) Fauna Britannica. Hamlyn, London.
  6. The Herpetological Conservation Trust. (2009) Widespread Reptiles Species Action Plan. The Herpetological Conservation Trust. Available at:
    http://www.arc-trust.org/downloads/Widespread_Reptile_SAP_Aug_09.pdf
  7. IUCN Red List (February, 2011)
    http://www.iucnredlist.org/