Pest Types

All information in this section of our website is taken from the Pest Fact Sheets which are published on the Harrow County Council website. We would like to thank the Harrow County Council Web Team for their kind permission allowing us to reproduce these fact sheets.

Snakes & Slow Worms

Snakes and slow-worms are relatively rare creatures which, while almost entirely harmless, can inspire fear in people who may be fond of most other sorts of animals.

They are reptiles, which means they are cold blooded and therefore rely on the heat of the sun to raise their body temperature to a level which enables them to become active.

Snakes and Slow-worms need to bask in the sun and they are most likely to be seen on dry, south facing banks, rockeries and other slopes.

The species which are found in Britain, are the Adder or Viper (Vipera berus), our only venomous snake; the Grass Snake (Natrix natrix); the Smooth Snake (Coronella austriaca) and the Slow-worm (Anguis fragilis).

The Adder
The Adder is a rather squat snake which grows up to a length of 47cm (19 inches) and can be readily identified by the wide zigzag dark or brown stripe along its back. It is spread widely throughout the British Isles (except Ireland where there are no snakes, banished it is said, by St Patrick). It prefers to live in scrubland, heathland and light woodland where it can find sunny areas to bask. Adders eat small mammals such as mice and voles, other reptiles and small birds, especially nestlings. The female adder produces litters of 6 to 10 young during August. Although the Adder has a venomous bite, it is very rarely fatal, about 1 person in 10 years, usually from an individual allergic reaction, out of a total of 100 incidents of snakebite each year. The bite causes swelling and irritation of the affected area, usually the hand or foot. Anyone bitten by an Adder should keep calm and seek medical advice.

The Grass Snake
The Grass Snake is our largest snake, growing up to 200cm (66 inches) in length. It is olive green or brown on its back, the belly is a checkering of black and white scales and it has rows of black spots on its back and sides. It also has bright yellow spots on its head where its 'ears' would be. Grass snakes live in England and Wales, not Scotland, and as well as dry areas such as heathland and woodland, will also live in wet areas, swimming in ponds and streams. It eats newts, fish, frogs and small mammals. The female lays two clutches of about ten eggs during the summer and the young Grass Snakes emerge 6 weeks to 2 months later. It is completely harmless and will usually avoid people.

Slow Worms
The Slow-worm, although it looks like a snake, is in fact a legless lizard. It differs from a snake in that its jaws cannot un-hinge like a snake's to swallow large prey and if caught by a predator, a Slow-worm can shed its tail like a lizard. Slow-worms grow up to 40cm (16 inches) in length. The skin is very smooth and has few markings apart from a dark stripe along its back. The body is brown or golden on top, the belly and sides being black or dark grey. It is widely distributed in Britain, and lives in and above dry ground. In towns, it can be found on railway embankments, particularly if they are south facing, and in compost heaps in gardens. It hibernates until March and the female gives birth to around 6 to 12 live young (see illustration). Slow-worms are common and abundant but they tend to keep hidden when not basking. They eat mainly slugs and snails, so can be seen as a gardener's friend. Although they can often be found living in ants nests, they do not eat ants. Slow-worms are completely harmless.

All these reptiles are protected species