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Pest Control - Snakes and Slow-worms


Grass Snake

Slow Worm


Grass snakes

Slow worm

What do the look like?

The adder (Vipera berus) can grow to 80cm. The colour of the snake is variable and differs between the sexes. The background colour is usually grey in males and brown in females. Both sexes have a thick, black zigzag pattern running along the length of the back.

The Grass snake (Natrix natrix) is the largest British snake, growing to about 150cm. It varies in coloration, but is usually a shade of green with short black vertical bars and/or spots running along its sides and sometimes along the back. It usually has a yellow, white or cream coloured collar behind the head, bordered to the rear by black markings.

The Slow-worm (Anguis fragilis) is a lizard with no legs that is often mistaken for a snake. They grow to 40cm and are brown or grey. The scales are small and smooth giving slow-worms a metallic or polished appearance. Females and juveniles have black or dark flanks and a thin black line running along the back. Adult males have a duller brown/grey background colour and usually lack the darker markings. Some males have a few blue spots that can be quite noticeable.

Where do they live?

The adder is found throughout the UK occurring most frequently on sandy heathlands and rough grassland slopes on free-draining soil.

The grass snake is found throughout much of Wales and central and southern England. Its preferred habitats tend to be associated with water (rivers, canals, lakes, ponds etc.) Compost heaps in gardens may be used as egg-laying sites, sometimes leading to mass emergence when the young appear in late August and September.

Slow-worms are fairly widespread throughout Britain and are found in a variety of habitats particularly grasslands and heathlands. Of all our native reptiles they are the most likely to be found in gardens and allotments. Although they may be noticed moving about on mild days, especially after rain, slow-worms spend most of their time underground or underneath objects lying around the garden.

What do they eat?

The adder mainly eats small mammals. The grass snake feeds mainly on amphibians and fish. Slow-worms feed mainly on slugs and are hence a friend of gardeners.

Pest Status

The adder is the UK’s only venomous snake, but because the venom is designed to kill only small animals like voles it is not particularly potent. Although adders should always be treated with respect, the danger of an adder bite is often exaggerated. Adders are only occasionally found in gardens due to their specific habitat requirements. If bitten hospital treatment is advised. Dogs and cats are unlikely to be seriously affected by an adder bite, but if you suspect that your pet has been bitten, take it to the vets for an examination.

Grass snakes and slow-worms are harmless and should cause no problems for humans.


All snakes are protected by law from killing and injury under the Wildlife and Countryside Act 1981. So if you come across a snake, do not harm it. If it is trapped or injured contact the RSPCA on 08705555999.

If you are concerned about snakes in your garden there are several points to consider.

  • Snakes (and lizards) pose little or no threat to people or pets

  • It is quite likely that the snake is just passing through your garden on a search for food, you may never see it again

  • Snakes usually glide off into the undergrowth when approached, they are more afraid of you than you are of them

In some circumstances it may be necessary for adders to be removed from gardens, for further information please contact
Froglife on 01733 558444 or via e-mail on

Last Updated: 21/02/2013
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