Grass Snake Grass Snake (Natrix natrix) Grass Snake © Darin Smith About The non-venomous grass snake is the largest British species of snake. Females mature at 4 years and are roughly 60cm, but exceptionally, really large ones exceed 120cm. Males tend to be slimmer and grow much beyond 80cm. They hibernate through the winter months, often together, under piles of vegetation, tree stumps, or in holes. They emerge in early spring to ask on sunny days. Reptiles in a cool climate need sunshine to raise their body temperature to a functional level, but they will always be close to thick cover. After mating in spring, the female will then lay her 50 eggs in a warm mound of vegetation such as a compost heap or manure heaps; the heat of fermentation speeds up development in the eggs. The young snake, 15 – 20cm long, emerge 6 – 10 weeks later. Diet Grass snakes are often found near water especially during the spring spawning seasons for amphibians, which they feed on. They will also eat fish, nesting birds and small mammals. How to identify/track? Due to the grass snake being the largest of the UK species of snakes, it is easier to recognise them. It differs from the adder, due to not having distinctive markings. Grass Snakes have a heart-shaped head. Did you know? Even though most predators eat prey head first, the grass snake starts with the back legs first. When threatened, grass snakes produce a foul-smelling substance or play dead in an exaggerated manner. Reserves where they are present Smallbrook Meadows, Langford Lakes, Jones's Mill, Pewsey, Penn Wood, Conigre Mead, Swindon Lagoons. Others in the Reptile Family Adder, Common Lizard Print out a copy of the Grass Snake Factsheet