Snakes in the UK: The 3 Native Species and Lookalikes

How many snakes live in the UK?

Great Britain has six native reptiles: three snakes and three lizards. The snakes are the adder (Vipera berus), the barred grass snake (Natrix helvetica) and the smooth snake (Coronella austriaca). The lizards are the common lizard, the sand lizard and the slow worm, which has no legs and is the reptile most often confused with a snake.

Ireland has no native snakes at all, which is why Northern Ireland has none. The reasons have more to do with the Ice Age and rising sea levels than with legend; see our guide to animals of Ireland.

Lengths are typical ranges; females of all three snakes tend to be larger than males.

Adder: Britain’s only venomous snake

The adder is a short, stocky snake with a dark zigzag stripe running down its back and a V or X-shaped mark on the head. Its eyes are red to copper with vertical pupils. Males are usually silvery gray or cream with a jet-black zigzag, while females are light to reddish brown with a dark brown zigzag. Some adders are almost completely black. Most are 50–65 cm (20–26 in) long, and British adders rarely exceed about 80 cm (31 in).

Adders live across mainland Britain, from Cornwall to the north of Scotland, but their distribution is patchy. They favor heathland, moorland, rough grassland, woodland edges and coastal dunes with plenty of cover and sunny spots for basking. They hunt voles, mice, lizards, frogs and nestling birds.

In Britain, adders hibernate through the winter, males for around 150 days and females for around 180. Males emerge first, often in February or March, and in spring rival males perform the famous “dance of the adders”, rearing up and pushing against each other. Adders give birth to live young, usually in late summer.

Adders have declined in many parts of Britain because of habitat loss, fragmentation and disturbance, and a citizen science survey found that small, isolated populations are the most at risk. In Great Britain, it is illegal to kill, injure or sell adders under the Wildlife and Countryside Act 1981. Across its huge range in Europe and Asia, the IUCN lists the species as Least Concern.

Are adders dangerous?

Adders are shy and not aggressive. Most try to slip away when they feel footsteps, and bites usually happen when someone picks one up or treads on one. Amphibian and Reptile Conservation estimates that 50–100 people are bitten in the UK each year, mostly between spring and fall, along with about 100 dogs.

A bite is painful and causes swelling, and it can make people, especially young children, seriously ill, so it always needs medical attention. Deaths are extremely rare: only 14 have been recorded in Britain since 1876, and the last was a five-year-old child in 1975. Read more in are adders dangerous?.

If someone is bitten, call 999 (or 112) immediately and seek emergency medical help, even if the bite seems minor.

Barred grass snake

Britain’s grass snakes were reclassified in 2017, when genetic studies showed that grass snakes in western Europe, including Britain, belong to a separate species, the barred grass snake (Natrix helvetica). Our grass snake profile covers the wider grass snake group.

It is Britain’s longest snake: adults are usually 70–100 cm (28–39 in) long, and big females can be longer. It is olive green to gray-green with black bars along its sides and a distinctive yellow or cream collar edged in black behind the head. Its pupils are round, and it has no zigzag.

Grass snakes are excellent swimmers and are usually found near ponds, lakes, slow rivers, ditches and wet meadows, as well as in gardens with ponds. They eat mainly frogs, toads and newts, and sometimes fish. They are Britain’s only egg-laying snake, laying batches of 8–40 leathery eggs in June and July in warm, rotting vegetation such as compost and manure heaps. The eggs hatch about 10 weeks later.

Grass snakes almost never bite. If caught, they release a foul-smelling liquid, and if that fails, they may play dead, going limp with the mouth open and the tongue hanging out.

Smooth snake

The smooth snake is the UK’s rarest snake and one of its most strictly protected animals. In Britain it lives only on sandy lowland heathland in southern England, mainly in Dorset, Hampshire and Surrey, with a few reintroduced populations elsewhere. It is a slim, secretive snake that spends much of its time hidden in heather and under cover, so even experienced naturalists rarely see one.

It is gray or brown with two rows of small, faint dark spots down the back, a dark crown-shaped mark on top of the head and a dark stripe running from the nostril through the eye. Its scales are flat and smooth, unlike the ridged scales of the adder and grass snake, which gives it its name. It has round pupils and no zigzag.

Smooth snakes feed mainly on other reptiles, especially lizards and young slow worms, as well as small mammals, and they hold larger prey in coils of the body. They give birth to live young in late summer. Because the species is fully protected by law, it must not be disturbed or handled without a license.

Slow worm: the legless lizard

The slow worm (Anguis fragilis) is neither slow nor a worm, and it is not a snake. It is a legless lizard, usually 40–50 cm (16–20 in) long, with a stiff, smooth, shiny body and no visible neck. Slow worms are gold, bronze, gray or copper. Females often have dark sides and a thin dark line down the back, and some males have blue spots.

Unlike snakes, slow worms can blink, and like many lizards, they can shed their tail if grabbed. They are common in gardens, allotments, churchyards, grassland and heath, and often shelter under compost heaps and sheets of metal or wood. They eat slugs, snails and worms, which makes them welcome in gardens. Slow worms give birth to live young in late summer and are remarkably long-lived: one kept at Copenhagen Zoo lived at least 54 years.

How to tell UK snakes apart

• Dark zigzag along the back: adder.
• Yellow or cream collar and black bars on the sides: grass snake.
• Plain gray or brown with faint paired spots and a dark eye stripe, on southern heathland: smooth snake.
• Shiny, smooth, no visible neck and able to blink: slow worm.

Size and setting help too. A long snake swimming in a pond is almost certainly a grass snake, while a short, thick snake basking on a heathland path is most likely an adder. For more detail, see adder vs grass snake.

Non-native snakes

Two small colonies of the Aesculapian snake (Zamenis longissimus), a harmless climbing snake from mainland Europe, have lived in Britain for decades: one near Colwyn Bay in north Wales and one beside the Regent’s Canal in London. Escaped pet snakes, such as corn snakes, also turn up from time to time, but they do not form wild populations.

Where and when to see snakes in the UK

British snakes hibernate from about October to February or March. The best time to see them is on sunny spring mornings, when they bask on banks and path edges to warm up before the vegetation grows tall. Lowland heaths in Dorset, Hampshire and Surrey, the New Forest, and moorland in Wales, northern England and Scotland are good places to look for adders, while wetland nature reserves are the best places for grass snakes.

Watch from paths with binoculars, keep dogs on a leash in adder country, and never pick up or chase a snake. Reptile surveyors often check sheets of metal and roofing felt laid on the ground, but lifting them disturbs the animals and, for smooth snakes, requires a license.