Reptile Survey

Reptiles in Britain

Reptiles, in Britain?!

Surprisingly, this is a common question asked by members of the public. There are in fact six species of native reptile: common European adder (Vipera berus), grass snake (Natrix natrix), smooth snake (Coronella austriaca), common lizard (Lacerta vivipara), sand lizard (Lacerta agilis) and slow worm (Anguis fragilis). The following article explains a little about their biology and ecology including a summary guide to their identification, habitat types, breeding and feeding habits and current threats to their populations. More detailed species accounts can be found by clicking the links below.

Common European Adder

Adders are a member of the Viperinae family. They are widely distributed in Europe, spreading as far as northern parts of Scotland. As the only venomous snake found in Britain, they received frequent persecution in the past, but their secretive nature and well-camouflaged skin usually minimise interaction with humans.

Identification and Habitat

Often described as ‘stocky’ snakes, adders can grow up to 70cm. Males are grey with black zig-zag markings and females are light brown with dark brown zig-zags. Juveniles are brick red with visible zig-zag stripes similar to adults. Adders They are generally found in open habitats with high levels of sunlight exposure including heathland, moorland and woodland with open corridors.

Breeding and Feeding

Unusually, adders do not lay eggs like most other reptiles and give birth to live young (viviparous). Juveniles are approximately 16cm and survive on the yolk sac and fat reserves they were born with, not feeding on live prey until the following year. The females feed continuously, in order to gain sufficient reserves for hibernation.

Once fully grown, adders have a variable diet of voles, most commonly field vole (Microtus agrestis), mice, eggs, amphibians and even lizards. While hunting for prey adders use a striking technique and quickly inject their venom, waiting for the subject to perish.

Grass Snake

Grass snake

Grass snakes are members of the Colubridae family and are widespread in both England and Wales. Considering that they are the largest terrestrial reptile present in Britain, with adults growing up to 70-120cm, they are notoriously difficult snakes to spot in the field as they are extremely sensitive to ground vibrations and well camouflaged.

Identification and Habitat

Body colour is variable ranging from bright green, dark olive or brown with a distinct cream/yellow collar and black markings to the rear. Most have black bars on their flanks, black spots on their back and distinct round pupils. Be aware that melanistic (black forms) and albinos can also occur.

Grass snakes are typically found in wetland habitats featuring lakes, streams and marshes; also present in heathland, woodland and drier habitats including gardens with a nearby pond, grassland and farmland.

Breeding and Feeding

Mating occurs April – May and females will then seek a suitable nest site in warmer areas such as manure and compost heaps. Females lay 10-40 eggs in one clutch and hatchlings arrive in late August – September with similar markings to fully grown adults. Grass snakes follow a seasonal diet feeding on fish during spring, newts during summer and frogs and toads for the latter months of the year. Juveniles will often feed on tadpoles.

Smooth Snake

Smooth snakeSmooth snakes are members of the Colubridae family like grass snakes. They are the least abundant snake in Britain with populations restricted to areas of Dorset, Hampshire and Surrey. Smooth snakes are an elusive and little studied species that tend to hide in crevices, under stones and loose soil.

Identification and Habitat

Slender snakes (45-55cm) with smooth, flat scales. Often identified by the distinct butterfly shaped marking on the top of their head and striking black eye stripe. Typically found in heathland habitats only. Their diet largely consists of lizards, voles, mice and other snakes. The juveniles only feed on reptile prey, further restricting their distribution to habitats suitable for other reptile species.


Little is known about smooth snake breeding behaviour. It is estimated that they breed around April – early June and unusually, they are ovoviviparous, whereby the female produces eggs internally and the eggs hatch inside the female. As a result, the female gives birth to live young and retains the eggs inside her body. This occurs September – October; later in the year than the adder and grass snake.

Slow Worm

slow wormThey are members of the family Anguidae and are one of the commonest reptiles in mainland Britain. As a legless lizard, they are often mistaken for a snake however, slow worms have both eyelids and ear openings that snakes lack. They grow up to 35-40cm.

Identification and Habitat

Usually grey or brown in colouration with a shiny appearance characteristic of smooth flat scales. Females are generally darker with dark brown sides and a stripe that is sometimes visible down the middle of their backs. Males are lighter and some show unique blue spots. Juveniles are similar to females but with more defined markings and a black spot on the top of their head.

Ideal habitat is underground in moist grassy areas or under vegetation litter. They are also found in gardens, woodland and wasteland. Slow worms feed on small invertebrates including slugs, snails, small insects and spiders


Mating occurs mid-May to late June and females give birth during late summer either on an annual basis or every other year. Similarly to smooth lizards, they are ovoviviparous and give birth to live young in a birth sac of up to a dozen juveniles. This process helps the embryos remain at a constant temperature during development, a factor not guaranteed for species that lay eggs (oviparous).

Common Lizard

Common lizardThey are members of the Lacertidae family and are the most common reptile in the UK. They are the only native species of reptile in Ireland. Adults can grow up to 15-16cm from nose to tail.

Identification and Habitat

Generally, brown with some variability: shades of yellow, red, green and black. Sexes are relatively simple to distinguish with males showing a flecked pattern on their backs, while females tend to have stripes. The underside of males are brightly coloured with dense black spots and females are yellow or grey, with few or no spots. Juveniles are dark brown or black. Be aware that young males can also appear green, causing confusion between common lizards and sand lizards.

Common lizards are found in a variety of habitats including heathland, woodland, grassland and coastal habitats. They mainly feed on insects and other small invertebrates.


Mating occurs April – May with young arriving in July. Common lizards are viviparous and give birth to live young, giving rise to their second commonly used name ‘viviparous lizard’.

Sand Lizard

Sand lizard_ male, female, juvenile (top to bottom)Sand Lizards are also members of the Lacertidae family but are rare in Britain with populations confined to areas in Dorset, Hampshire and Surrey and sand dunes covering the Mersey Coast. Larger than the common lizard, they grow up to 16-19cm from head to tail.

Identification and Habitat

Generally, brown in colour with distinct dark markings with light centres known as eyespots. Sand lizards have three rows of eyespots; along with their back and on both flanks. During breeding season in spring, males are bright green on their flanks. In contrast, females are sandy brown with dark markings and lack the green colouration of males.

In the UK, they are restricted to heathland and coastal dune habitats; however, they are also found utilising grasslands and meadows.

Mating occurs May – June and unlike the common lizard, they are oviparous and lay eggs in sandy burrows. They feed on insects and other small invertebrates.

Our ecologists have extensive experience in surveying for reptiles and designing mitigation. We can advise you on survey methodology, legal protection, mitigation options and the timing of development works.

For more information about the Ecology Services, we can offer, call us on 029 2065 0331 or contact us on

Adder Grass Snake Smooth Snake

Slow Worm Sand Lizard Common Lizard