Grass snake or adder? How to tell the difference between UK reptiles
by Karen Hornigold , Assistant Conservation Adviser - Data & Information
on 1 February 2018
The UK has three native species of snake and three species of lizard. Learn which reptiles are native to the UK, where they are found and how to spot them.
Firstly it is important to differentiate between the two groups in the reptile order Squamata - the snakes (Serpentes) and the lizards (Lacertilia). Briefly, snakes have no eyelids or ear openings, a long thin forked tongue and no limbs, whereas lizards have moveable eyelids, ear openings, a long thick forked tongue and two pairs of limbs (except limbless lizards).
Native UK snakes
Adder (Viper berus)
Adders are clearly distinguished by a dark zigzagging line down their back set against a grey (male) or light brown (female) body. They also have a ‘V’ or ‘X’ shaped marking on the head.
Adders are venomous, but adder bites are rare and seldom fatal. No other snake species in the UK is venomous, so it’s worth being able to recognise them! However, adders are secretive and well camouflaged so it’s unlikely you’ll come across them often.
They live in open habitats where they can bask in the sun, such as heathland, moorland and open woodland.
Male adder (Photo: WTML/ Dennis Johnson)
Find your nearest wood
Grass snake (Natrix natrix)
Grass snakes do not have the dark zigzag down their backs like adders, making them easy to tell apart. Grass snakes are grey-green coloured with black bars down their sides and a yellow and black ‘collar’ around the neck.
They are found throughout England and Wales, but not Scotland, and live close to water as they feed on amphibians and fish. As such they may be found near garden ponds. Don’t worry though - grass snakes are not venomous and are very shy; if cornered they tend to play dead!
Grass snake (Photo: WTML/ Libby Owen)
Smooth snake (Coronella austriaca)
Smooth snakes are extremely rare, found only in heathlands in Dorset, Hampshire and Surrey. They hide under stones and logs rather than basking in the open. If you are fortunate enough to see a smooth snake, they are grey-brown, with two rows of black markings down their back and a heart-shaped crown on the head. They are browner than grass snakes and the black markings are on their back rather than their sides.
Smooth snakes are strictly protected by European law and reintroduction programmes are trying to save this species from extinction in Britain.
Smooth snake (Photo: WTML/ Peter Holmes)
Native UK lizards
Common lizard (Zootoca vivipara)
Common lizards are brown (but can also be yellow, green and black) with dark spots or stripes running lengthways down the body. They are typically 15 cm in length from nose to tail. As its name suggests, it is widespread throughout the UK, living in commons, heaths, moorland, dry stone walls and sea cliffs.
Common lizard (Photo: WTML/ Laurie Campbell)
Slow-worm (Anguis fragilis)
Slow-worms are legless lizards and so are often mistaken for snakes. However, check if it blinks – this is a dead giveaway that it’s a lizard as snakes don’t have eyelids.
Males are grey or brown, sometimes with bright blue spots, whilst females are golden brown, often with a thick dark line down their back. Slow-worms hide under logs or compost heaps, rather than basking in the sun, and may be found in gardens.
Slow-worm (Photo: WTML/ Amy Lewis)
Sand lizard (Lacerta agilis)
Like the smooth snake, the sand lizard is found only in Dorset, Hampshire and Surrey as it requires heathland and dune habitats in close proximity. There have been reintroductions also for this species to try to extend its range and expand the UK population.
The sand lizard is brown with extremely bright green sides, which help to distinguish it from the common lizard. It’s also larger, reaching 20 cm in length.
Sand lizard (Photo: Wikimedia Commons)
All UK reptiles are protected by national law, which makes it illegal to deliberately kill, injure or sell individuals of any species. They are fantastic to spot, but please observe them from a distance and do not disturb unnecessarily.