Species Guide: European Grass Snake (Natrix helvetica)
Family: Colubridae
APPEARANCE
The Grass Snake is typically olive-green or grey on its upper parts with black markings down its sides. Females are typically bigger than males. They are frequently misidentified as Adders, but a good differentiator is typically the black and yellow collar markings, though this can be missing on some Grass Snakes.
Interestingly, the Grass Snake population in Central Europe was given a specific designation Natrix helvetica in 2017 due to unique hybridization patterning1. Further, the UK population is designated as a sub-species of the European population Natrix helvetica helvetica for the same rationale.
Another differentiator to look out for on the Grass Snake is its round eye and pupil.
Diet
Grass Snakes have a varied diet based on seasonal food availability. They tend to take fish during the spring, moving to newts in the early summer, then frogs and toads in late summer. They are also known to catch small mammals such as mice and voles2.
HABITAT
The Grass Snake is common in England and Wales. Originally it was thought that they were not present in Scotland or Ireland, though sightings have been reported in Scotland, and it is now suspected their range has expanded3.
They favor areas where there are water bodies, though research has demonstrated they will inhabit a range of environments including woodland/agricultural interfaces, hedges, gardens, agricultural buildings, and manure heaps.4
Note that this map is for a rough illustration of animal distribution across the UK. Dark green indicates established populations and lighter green indicates possible range expansion.
Behavior
Grass Snakes will rarely bite in defense, though they will put on a show of aggression by inflating their bodies, and hissing at their aggressor. They will also feign death to dissuade a potential predator from eating them, and if further provoked, will secrete a smelly discharge from their cloaca (vent). 5
They hibernate during the winter, emerging in March or April to start feeding, and in search of a mate. Grass Snakes are egg layers, the female will lay up to 40 eggs during June or July in rotting vegetation to keep them warm. The eggs hatch approximately ten weeks later, are approximately 18 cm in length, and are immediately independent.6
Biometrics7
| Body Length | 90-150 cm |
| Body Weight | 240 grams |
| Longevity | 15-25 Years |
NATURAL PREDATORS
Grass Snakes have numerous predators including Badgers, Foxes, Hedgehogs, Pine Marten, Crows & Owls.
Conservation Status
The Grass Snake is protected under the Wildlife and Countryside Act 1981. It is registered as Least Concern by the IUCN8.
Global
Conservation Status
CITATIONS
- Kindler, C. et al. (2017) ‘Hybridization patterns in two contact zones of grass snakes reveal a new Central European snake species’, Scientific reports, 7(1), pp. 7378–12. Available at: https://doi.org/10.1038/s41598-017-07847-9. [Accessed 02/03/2025] ↩︎
- Patrick T. Gregory and Leigh Anne Isaac “Food Habits of the Grass Snake in Southeastern England: Is Natrix natrix a Generalist Predator?,” Journal of Herpetology 38(1), 88-95, (1 March 2004). https://doi.org/10.1670/87-03A [Accessed 02/03/2025] ↩︎
- Have you seen a grass snake in Scotland? ArgUK ↩︎
- Reading, C. and Jofré, G. (2009) ‘Habitat selection and range size of grass snakes Natrix natrix in an agricultural landscape in southern England’, Amphibia-reptilia, 30(3), pp. 379–388. Available at: https://doi.org/10.1163/156853809788795164 [Accessed 02/03/2025] ↩︎
- Milius, S. (2006) Why play dead?: Rethinking what used to be obvious, Science news (Washington). Washington, DC: Society for Science & the Public, pp. 280–281. Available at: https://doi.org/10.2307/4017568. [Accessed 02/03/2025] ↩︎
- Brown, Peter Ronald (1991) Ecology and vagility of the grass snake Natrix natrix helvetica Lacépède. University of Southampton, Doctoral Thesis. [Accessed 02/03/2025] ↩︎
- Wildlife Trust | Grass Snake [Accessed 02/03/2025] ↩︎
- IUCN Redlist | Grass Snake [Accessed 02/03/2025] ↩︎
References
Speybroeck, J. et al. (2016) Field Guide to the Amphibians and Reptiles of Britain and Europe. 1st edn. London: Bloomsbury Publishing Plc. [Accessed 02/03/2025]
