Field Guide
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Grass Snake
Natrix helvetica
Not yet photographed by the community
UK's longest snake; yellow collar and loves water.
Species Profile
Protected under the Wildlife and Countryside Act 1981; UK conservation status is Least Concern, though locally threatened by habitat loss and persecution.
- Lifespan
- 10–15 years in the wild, up to 20 years in captivity
- Size & Weight
- 60–90 cm (females larger than males); occasionally exceeding 1 m; 50–150 g
- Habitat
- Wetland and semi-aquatic environments including ponds, ditches, marshes, reed beds, and damp meadows, often near water but adaptable to various habitats.
- UK Distribution
- Found throughout England, Wales, and southern Scotland; largely absent from northern Scotland. Resident year-round but less active in winter months; range expanding northwards.
- Diet
- Primarily amphibians such as frogs and newts; also small fish, occasionally small mammals and invertebrates.
- Prey
- Common frogs, smooth newts, great crested newts, sticklebacks, tadpoles, insects
- Predators
- Badgers, foxes, herons, grass snakes are often preyed upon by larger snakes, particularly adders in sympatry; young vulnerable to corvids and shrikes
- Mating Season
- April to May
- Breeding
- Females lay 8–40 elongated white eggs in June–July in warm, moist locations such as compost heaps or rotting vegetation; incubation takes 6–10 weeks; single clutch per year.
- Behaviour
- Grass snakes are semi-aquatic and excellent swimmers. They are diurnal and relatively docile, often playing dead (thanatosis) or releasing foul-smelling musk when threatened. They bask in sunny locations to thermoregulate.
- •Grass snakes can hold their breath underwater for extended periods, allowing them to hunt submerged prey and escape predators.
- •When threatened, they flatten their bodies and hiss loudly to appear larger and more dangerous—they are, however, entirely harmless to humans.
- •Females migrate considerable distances to find suitable egg-laying sites, sometimes travelling over 1 km.
- •Unlike many reptiles, grass snakes have no colour-change ability, but individuals vary from green to brown to grey with characteristic yellow and black neck markings.
- •They are the only British snake species that regularly enters water; their specialised diet of amphibians reflects their semi-aquatic lifestyle.
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