Snakes in the UK: Just Three Native Species

Britain is a reassuring place for anyone wary of snakes. The United Kingdom has only three native snake species, and just one of them is venomous. Bites are uncommon and rarely dangerous. This guide covers all three so you can tell them apart and know what, if anything, to worry about.

Only three native snakes

The UK's native snakes are the adder, the grass snake, and the smooth snake. That is the complete list. Compared with the dozens of species in many countries, three is a very short list, and it makes identification straightforward. You may occasionally hear of other snakes in Britain, but those are escaped or released non-native pets, not established wild species.

• The adder, the only venomous native snake, recognized by a bold dark zigzag down the back
• The grass snake, a longer, harmless snake usually with a yellow-and-black collar behind the head
• The smooth snake, a rare, slender, harmless snake of a few southern heathlands

The adder, the only venomous one

The adder is the UK's only venomous snake. It is a small viper with vertical pupils and a distinctive dark zigzag stripe running the length of its back, set against gray, brown, or reddish coloring. Adders are shy and spend much of their time basking quietly; they bite only when trodden on or handled. An adder bite is painful and should always be checked by a doctor, but it is rarely fatal, and deaths in Britain are extremely rare.

The grass snake

The grass snake is Britain's longest snake and is completely harmless. It is usually greenish or olive with a pale yellow-and-black collar just behind the head, and round pupils. Grass snakes are strong swimmers, often found near ponds and rivers where they hunt frogs and fish. When alarmed they may hiss, release a foul smell, or play dead by flipping over, but they do not pose any danger to people.

The smooth snake

The smooth snake is the rarest of the three and the one you are least likely to ever see. It is a slim, gray-to-brown, harmless snake confined to a few sandy heathlands in southern England. It can look superficially like an adder but lacks the bold zigzag, instead showing a more subtle pattern of dark markings. Because it is so localized and protected, most people in Britain will never encounter one.

Adder or grass snake?

The two snakes you might realistically meet are the adder and the grass snake. The quickest tell is the back: a bold continuous zigzag means an adder, while a plainer body with a yellowish collar means a grass snake. Size helps too, as grass snakes grow noticeably longer. When in doubt, keep your distance and use our identification tool rather than handling the snake.

What about other reptiles?

Britain also has a legless lizard called the slow worm, which is frequently mistaken for a snake. It is harmless and easy to tell apart with a close look: slow worms have eyelids they can blink and can shed their tails, neither of which snakes can do. They are smooth, shiny, and usually gray or bronze. If you find a small, glossy, snake-like animal in a garden or compost heap, it is far more likely to be a slow worm than any of the three true snakes. Our snake or legless lizard guide explains the differences in more detail.

It is also worth remembering that adders have declined across much of Britain and are now a conservation concern in many counties. Far from being a menace, the adder is a shy animal that most people will go their whole lives without seeing. Harming any of the three native snakes is illegal, and there is no good reason to do so: they control rodents and pests and are a valued part of the British countryside.

With only three native species and a single mild venomous one, the UK is among the safest countries in the world for snake encounters. Knowing the adder's zigzag is really all most people need. For more on Britain's reptiles and how it compares to other regions, see the United Kingdom country page and browse other country guides.