The grass snake (Natrix natrix) is one of Europe’s most common reptiles. This non-venomous snake is a familiar sight in the countryside and suburban gardens, though its timid nature means it often goes unnoticed. As a semi-aquatic species, it is frequently found near water where it hunts its prey. The grass snake is harmless to humans and possesses unique defensive behaviors.
Physical Characteristics
A defining feature of a grass snake is the collar just behind its head. This band is yellow, white, or pale orange, often bordered by a black band. This marking is more vivid in younger snakes and can fade as the animal ages. The snake’s body is olive-green, brown, or grey, with dark, vertical bars or spots along its flanks.
A significant size difference exists between the sexes. Females are larger, often growing to lengths of 90-110 cm, while males are slimmer and measure around 50 cm. The underside of a grass snake is a whitish or pale grey color, marked with irregular black blocks that can be used to identify individual snakes.
To identify a grass snake, it is helpful to distinguish it from the UK’s only venomous snake, the adder (Vipera berus). The adder is stockier, with a distinct dark zigzag pattern running down its back and a V or X-shaped marking on its head. Adders also have vertical, cat-like pupils, whereas grass snakes have round pupils.
Habitat and Geographic Range
Grass snakes have a vast distribution across mainland Europe, from central Scandinavia to southern Italy and east into parts of the Middle East and Asia. In the United Kingdom, they are common throughout England and Wales but are absent from Scotland and not native to Ireland.
This species prefers habitats close to water. Ponds, lakes, canals, marshes, and slow-flowing rivers are ideal environments. Their association with water is so strong that their scientific name, Natrix, is derived from the Latin word for “to swim.”
Beyond wetlands, grass snakes are adaptable and can be found in grasslands, open woodlands, and farmland. They are also frequent visitors to gardens, especially those with ponds or compost heaps. The heat from decaying vegetation in a compost heap provides a natural incubator for the snake’s eggs, laid in early summer.
Diet and Behavior
The grass snake’s diet is linked to its aquatic lifestyle, primarily consisting of amphibians. Frogs, toads, and newts are their main food source, which they hunt in and around water. They are proficient swimmers and will also prey on fish and, on occasion, small mammals or bird chicks.
Grass snakes are diurnal, meaning they are most active during the day. Much of their time is spent basking in the sun to regulate their body temperature. When confronted by a threat, their first instinct is to escape. They are shy and will almost never bite in defense, though they might perform a mock strike with a closed mouth.
If cornered, a grass snake employs several defensive tactics. It can release a foul, garlic-smelling liquid from its anal glands. Its most famous defense is feigning death, a behavior called thanatosis, where the snake will go limp, often turning onto its back with its mouth open. During the winter months, from October to April, grass snakes hibernate in sheltered, frost-free locations like tree root systems or compost heaps.