Grass snake, Natrix natrix
(Linnaeus, 1758)

History and origin
The Grass snake was first described by Linnaeus in 1758. The scienfitic name of this species is Natrix natrix. Natrix is latin for swimmer, water loving, named thanks to their aquatic habits of this species.

Characteristics
They are characterised by the yellow collar on their neck which is more vivid for juveniles.

Description
=Size=
They hatch at around 20 cm long, averaging about 100 cm long but growing up to 180 cm long.
=Morphology=
They are slim and elegant as juveniles and young adults, however when the reach a length of around 100 cm long, their body becomes much more robust, especially for females. Their head is large and triangular. They have large scales on the top and side of their head and a large eye.
=Patterns & colours=
They are green or olive-green with various black markings on their flanks and they have a black and yellow collar. The variations in patterns and coloration depends on the subspecies. Their belly is checkered black and white.

Geographical range
Very widespread, absent in the Balearics, Crete, northern England and Scotland, Ireland, all except southern and extreme southern Sweden and Norway, absent in the northern half of Finland.

Subspecies:

  • - astreptophora - Found in Portugal, Spain and in a small area of France (departments of Pyrénées-Orientales and the lower half of Aude. Northern limit Narbonne).
  • - cetti - Found on Sardinia in the Mediterranean.
  • - corsa - Found on Corsica in the Mediterranean, was recently separated from the sub-species cetti.
  • - fusca - Only found on the small Greek island of Kea.
  • - gotlandica - Found on the Swedish island of Gotland.
  • - helvetica - Found over the French mainland (except for a small area where Astreptophora occurs), most of Switzerland (except far east, replaced by Natrix), west of the Rhine river in Germany, Belgium, Luxembourg, the Netherlands, england and Wales.
  • - lanzai - Found in Italy (except from the north, replaced by natrix and helvetica).
  • - natrix - Found from the Rhine river in Germany eastwards into Russia, the southern limits are extreme east Switzerland, northern Italy, north Slovenia, Hungary, and northern Romania. To the north this sub-species is present in Denmark, Finland, Norway and Sweden.
  • - persa - Found in the Balkan peninsula, northern limit is where the southern limit of natrix occurs (see natrix).
  • - schweizeri - Found on several greek islands: Milos, Kimolos and Polyagos.
  • - sicula - Found on the island of Sicily in the Mediterranean.
  • Sexual differences
    Females are longer and larger then the males, especially in late spring when they carry their eggs.

    Seasonal variations
    Females are larger in spring due to their eggs.

    Diet
    Their main food source are amphibians of all genres, they eat mainly Pelophylax species. Fish are also hunted. Sometimes in dryer habitats, small rodents such as mice can be taken. Young snakes will feed on large water insects and more commonly tadpoles and small fish.

    Defensive habits
    They may hiss loudly, emit a foul smelling liquid from the anal region and some feint death, pulling out their tongue, mouth wide open, this often works at tricking their predators into leaving them alone. Sometimes, a specimen may want to pass its self off for a viper and try the more aggressive looking techniques to get its self out of trouble, this includes flattening their neck and head, hissing loudly and swinging out towards the predator as if it wanted to bite, however experience shows that they keep their mouth closed on 99% of their strikes.

    Reproduction
    Breeding occurs when the snakes wake up from hibernation in spring, a week after, they are all looking for each other and mating begins. After only a few weeks about 50 eggs are laid (extremes are from 5 to 100 eggs) in a moist, warm spot, usually under hey piles, in rotting wood piles and other places of this kind. The eggs incubate for around 8 weeks before hatching.

    Sexual maturity, life span
    The average life span for Natrix natrix is about 25 years, males reach their sexual maturity in their third year whereas females mature in their fifth year at the earliest. The specimens are about 60 cm long when they reach sexual maturity.

    Habits
    They are a semi-aquatic snake, the least aquatic of the three species family ‘Natrix’, they are sometimes found up to 3 km away from water, it is in these areas that they feed on Bufo bufo or mice, they are however more common near water bodies. They are diurnal and enjoy sunbathing in the morning sun like all other snake species. When they are disturbed they usually swim away at high speed, they usually avoid diving, opting to stay on the water surface, this can be used as a reference when observing this species, it is possible to see them from far away with binoculars on a calm lake or pond.

    Venom
    This is a non-venomous snake.

    Habitat
    They live in moist areas usually very close to water in the form of streams, rivers, ponds... But also sometimes found in dryer habitats away from water.

    Predators
    Their natural predators are various mammals such as foxes and wild cats, also birds of prey and carnivorous water insects for the juveniles.

    Grass snake - © Daniel Phillips
    Grass snake, Natrix natrix helvetica - © Daniel Phillips

    Grass snake - © Daniel Phillips
    Grass snake, Natrix natrix helvetica feignting death - © Daniel Phillips

    Grass snake - © Daniel Phillips
    Grass snake, Natrix natrix helvetica - © Daniel Phillips

    Grass snake - © Daniel PhillipsGrass snake, Natrix natrix astreptophora - © Daniel Phillips

    Grass snake - © Daniel Phillips
    Grass snake, Natrix natrix astreptophora - © Daniel Phillips

    Grass snake - © Daniel Phillips
    Grass snake, Natrix natrix astreptophora - © Daniel Phillips