Britain's largest reptile is shy by nature and wary of humans. You might spot these sun-loving basking on grassy banks on warm summer days.
Grass snakes 'play dead' when threatened, curling up with their tongue lolling out their mouth.
Grass snake facts
Scientific name: Natrix helvetica
Family: Colubridae
Diet: Amphibians, fish, small mammals, and birds
Predators: Badgers, red foxes, domestic cats, hedgehogs, and birds of prey
Size: 90-150cm
Weight: 240g
Lifespan: 15-25 years
About grass snakes
Grass snakes are one of three snakes found in the UK. These docile creatures don't bite and are harmless to humans.
Even when threatened, grass snakes might strike out their heads with their mouths closed, releasing a foul-smelling substance, turning and running, or 'playing dead'. This theatrical performance sees the snake writhing onto its back and lolling its tongue out of its mouth.
Grass snakes and our canals
Grass snakes, as the name suggests, are often found in grasslands, as well as open woodland and gardens. However, they have a particular fondness for wetland habitats, such as lakes, rivers, ponds, and canals.
These large reptiles are extremely strong swimmers, often seen making their way across our canals.
Grass snakes are typically grey-green with a distinctive yellow and black collar (more obvious on juveniles), pale underside, and dark markings along the body. They can grow well beyond a metre long, and females are larger than males.
A grass snake with a green-brown body and black markings curls up, sticking out its forked tongue.
Without venom, grass snakes rely on the element of surprise, adopting a 'sit and wait' hunting policy. They catch any unsuspecting prey daring to venture within striking distance in their large jaws and swallow it whole, often while still alive.
Although they favour frogs, toads, and newts, grass snakes will also eat fish, small mammals, and birds. Studies suggest that adult grass snakes can survive for 12 months on fewer than ten frogs.
How do grass snakes breed?
The UK's only egg-laying snakes, females can lay 10-40 eggs within rotting vegetation in a sheltered location, like compost heaps. They incubate the eggs until late summer or early autumn.
Few young reach adulthood, with many falling prey to herons, birds of prey, and other hungry predators.
Grass snakes like wet habitats, spending a lot of their time in open water or near bodies of water.
Where do grass snakes live?
Grass snakes inhabit damp habitats around most of the UK, excluding Scotland. They prefer to make their homes on canal and river banks, ponds, or ditches, but you might also spot them in hedgerows, meadows, and along the edges of woodlands.
These reptiles are as happy on land as they're in water, often spotted basking in the sun on the towpaths or swimming across the canal.
As cold-blooded creatures, grass snakes spend the coldest months in hibernation. They prefer warm, humid environments, like tree root systems, under fallen trees, in compost heaps, or making use of rabbit warrens. They typically hibernate from October or November to March.
Grass snakes are shy, quickly retreating when they detect humans. However, you might see one on our towpaths or swimming across the canals.
What's the best time of day to spot grass snakes?
As snakes are cold-blooded, they have to bask in the sun to generate warmth. Your best chance to spot a grass snake is in the early morning when they're sunbathing. If you do see a grass snake sunning itself, it's worth revisiting as they tend to reuse the same basking spots.
What's the best time of year to spot grass snakes?
Grass snakes hibernate for the winter, reawakening in the spring. Head to water-side habitats from April to September to catch sight of a grass snake.
Unlike adders and smooth snakes, grass snakes don't have black markings on their backs.
What's the difference between a grass snake and an adder?
The UK has three native snake species: the grass snake, the adder, and the smooth snake. Adders are distinguished from grass snakes by the dark zigzagging markings on the back. Smooth snakes are rare, recognisable by their slender build, round pupils, and less-well-defined dark pattern on the back.
Slow worms are also often mistaken for grass snakes, even if they're not actually snakes but legless lizards. Slow worms can be identified by their smaller body and bullet-shaped heads.
