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Species native to the United Kingdom
Introduced or alien species
Alien species that present a threat to wildlife

Grass Snake - Natrix helvetica* - Native



Reptile - Non-Venomous Snake

Distinct yellow/cream/white and black Collar around neck

Round pupil

Dorsal surface and flanks, olive green/green with distinct bars

May appear very dark before skin shedding (sloughing)

Ventral surface, white/cream with black chequers, some individuals have an almost entirely black underside.

Some colour variation occurs, the most distinctive features of the Grass Snake are the black and yellow/cream/white crescent shaped collar on the neck and its long slender appearance.

The light part of the collar marking is occasionally missing, particularly in older females, the black crescent part of the collar is always present.

Length: The Grass Snake is the largest indigenous reptile in the UK, typically males reach 100 cm, females up to130 cm, though larger individuals have been recorded.

Grass Snake - identification
© 2003 Gemma Jane Fairchild RAUK

Grass Snake - female
© 2003 Gemma Jane Fairchild RAUK

* Until recently, the UK Grass snake was classified as Natrix natrix helvetica. But, with genetic sequencing based on mitochondrial and nuclear microsatellite DNA described in a recent paper by Kindler et al., (2017) the British animal (in fact, basically the western European) has been elevated to full species status and our sub-species is now Natrix helvetica helvetica. The relevant paper can be found by clicking here.


Males are smaller than females but have a relatively longer tail in comparison. Males have noticeable swellings at the vent. The Grass Snake may be sexed by a sub-caudal scale count, males have 68-72 sub-caudal scales, females 52-56.

Grass Snake - male
© Alan Hyde


Eggs are laid in June and July. The female may lay up to 40 leathery matt-white eggs, often choosing compost and manure heaps as the warmth acts as a natural incubator. The eggs measure from 23-30mm. The hatchlings emerge in autumn.

Eggs of the Grass Snake
Grass Snake - eggs
© Tony Phelps Reptile Research & Imagery

What else could it be?

Often confused with the Adder (Vipera berus) the Grass Snake is a non-venomous and harmless creature. The Adder has a more thickset body, a distinct zigzag stripe down its back and a V or X shape marking on the head. The Adder may also be distinguished by its vertically slit pupil.

Sometimes the Grass Snake is confused with the Slow-worm (Anguis fragilis), which is a leg-less lizard and not a snake at all. The Slow-worm is a smaller creature (40 - 45cm) with a glassy grey/brown appearance.

Grass Snake - female
© Tony Phelps Reptile Research & Imagery

Female Grass Snake showing neck marking and slender appearance.

Where will I see a Grass Snake and is it dangerous?

The Grass Snake favours rough land and pastures, usually close to a standing body of water. Feeding almost exclusively on amphibians, some individuals may take small fish. The Grass Snake is an occasional garden visitor.

Grass Snakes only show aggression if cornered, hissing loudly and recoiling into a position that looks like they may strike. This is bluff, they rarely bite and if handled often play dead. As with all our native snakes, the best option is simply to leave the snake to get on with its daily business.

Grass Snake - feigning death
Picture reproduced with the kind permission of Paolo Mazzei

Feigning death. This is one of the defensive tactics used by the Grass Snake, others are hissing loudly and exuding a foul smelling liquid from the anal vent if captured.

Grass Snakes are harmless and protected under the Wildlife and Countryside Act 1981.

It is an offence to kill, harm or injure them

sell or trade them in any way

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