North York Moors

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Adder

Cotton grassCotton grass
Scientific name

Adder (Vipera berus).

Habitat

Moorland, woodland, hedgerows, river banks, sand dunes and mountains. Although they live in a variety of habitats, they prefer undisturbed areas.

Appearance

The adder is Britain’s only poisonous snake and grows up to about 60cm in length. Its skin is made of tough scales and, from time to time, as the adder grows it wriggles out of its old skin and grows a new, bigger one. If you are lucky you could find an empty adder skin on the ground. Adders vary in colour – some are brown, some are grey and some are black. They have a dark zig-zag line along the back, which helps with camouflage, and a V mark along the back of the head.

Lifestyle

Like all reptiles adders are cold-blooded and depend on the warmth of the sun to warm their bodies. Early in the day they bask in the sun to warm up and as the day becomes hotter they move into the shade to cool down. Adders survive cold winters by hibernating from October to March in a cool, dry place, usually a hole or crevice in the ground. A group will often hibernate together. 

Their bodies are highly sensitive to vibrations in the ground and this helps warm them of danger. Adders usually hunt for food during the daytime. Their prey includes lizards, amphibians, young birds and small mammals such as mice and voles. They kill with a bite from their fangs, which injects venom into the victim and paralyses it – usually the adder swallows its prey whole. Adders do not eat every day; a large meal may last a week or more.  

Female adders give birth to between 3 and 20 baby adders in August. The babies stay close to their mother for a few days and then slither away to look after themselves.

Conservation

Adders are protected under the Wildlife and Countryside Act 1981 and must not be killed, injured or sold.  

If you are walking on moorland on a warm summer day, keep a careful eye on the path in front of you. If you are lucky enough to see an adder, keep still and don’t try to touch it. It will probably be more frightened of you and will disappear into the heather. Usually adders know when you are coming. They are deaf, but they can feel the vibrations of footsteps through the ground. It’s often the sleepy ones we see along the paths. 

Adders are very shy and will only attack if threatened. Very few people have ever been killed by the bite of an adder; however the bite is painful and requires urgent medical attention.