Reptiles we may see in our gardens

The British Isles has (a good pub quiz answer) six native species of reptile, comprising three snakes; the common European adder (Vipera berus), the grass snake (Natrix helvetica) and the smooth snake (Coronella austriaca)), and three lizards; the common lizard (Lacerta vivipara), sand lizard (Lacerta agilis) and the slow worm (Anguis fragilis). 

Both the smooth snake and the sand lizard are very rare and confined to particular dry sandy heathland habitats, such as in parts of Dorset, Hampshire and Surrey. The adder, grass snake, common lizard and slow worm are all present around East Harptree. This article focuses on our two local snake species, the adder and grass snake, both of which are protected in the UK from killing, injury or trade under the Wildlife and Countryside Act, 1981 and are listed as Priority Species under the UK Post-2010 Biodiversity Framework. Their habitats are not protected. 

The Adder 

The adder is a readily identified snake of the viper family (Viperinae) which is found across the globe. While most are venomous and some are highly dangerous, the UK adder is not aggressive and human bites are uncommon. Their well-camouflaged skin and secretive nature means that they are rarely seen and can actively avoid interaction with humans, tending to glide out of sight rather than use energy to challenge human disturbance. If taken by surprise by dogs running through their favoured habitat they may bite, which can prove fatal for the dog if not treated. 

Adders can grow up to about 70cm in length and are quite ‘stocky’, with a short tail. Males are grey with characteristic black zig-zag markings and females are light brown with dark brown zig-zags. They are generally found in open habitats with high levels of sunlight exposure, preferring undisturbed areas of heathland, moorland, rough grassland, and woodland with open corridors. (see images below).

The grass snake 

The grass snake is the largest UK reptile; longer and slimmer than the adder it can reach a length of up to 1.2m. Body colour ranges from bright green, dark olive or brown with a distinctive cream or yellow collar around the back of the head. Most have black bars on their flanks, black spots on their back and distinct round pupils (easily distinguished from the adder which has narrow vertical pupils).

Grass snakes are in the Colubridae family, the largest of all the world’s snake families, and are found on every continent except Antarctica. Whilst some are venomous many, including our own grass snake, are harmless. Historically assigned to the subspecies Natrix natrix helvetica, the British population of grass snake is recommended to be elevated to full species status as Natrix helvetica, also known as the barred grass snake.

Typically found in wetland habitats, and near ponds, lakes, streams and marshes, grass snakes use drier habitats including heathland, woodland and gardens, especially if there is a nearby pond and grassland. The area around East Harptree offers many such habitat opportunities. Although a relatively abundant species, the grass snake is notoriously difficult to spot. The best chance to see one is in summer, basking in the sun near their favourite pond or swimming in the water.

Typically hibernating from October to April, grass snakes mate in April and May. Unlike the adder the female grass snake lays a clutch of 10-40 eggs in a warm nest site, such as a garden compost heap, which offers ideal nesting habitat, retaining warmth and moisture over the six to ten weeks gestation period before hatching around August.

If you come across a cluster of rubbery eggs amongst your garden and kitchen arisings, please don’t disturb them. The eggs in the image below were found when turning the compost and carefully re-buried in the compost pile to continue to develop.

Grass snakes follow an interestingly seasonal diet, preferentially feeding on fish (if available) during spring, newts during summer and frogs and toads for the latter months of the year. Juveniles will often feed on tadpoles. It is not an uncommon occurrence to find a grass snake in a garden pond. No, it has not fallen in – they are great swimmers and it is probably hunting for food.

Like adders, grass snakes can be long lived, at up to 25 years. Previously abundant, their population has fallen over recent decades, largely due to development, habitat disturbance, and predation. When threatened by a predator, commonly cats, foxes, badgers and some birds, the grass snake can “play dead”, appearing lifeless and making itself less appealing to eat. If captured it may hiss and release a smelly substance from its anal gland. Although they may also strike with the head, grass snakes do not bite and are harmless to humans.

For more information see Amphibian and Reptile Conservation’s excellent guides to the Adder and Grass Snake: https://www.arc-trust.org/pages/category/snakes

Thank you to the East Harptree Environment Group for this article.