By Kevin Parr

Published: Tuesday, 10 January 2023 at 12:00 am

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Despite its appearance, the slow worm is not a snake (or a worm) but a legless lizard. This is apparent by the fact that it has eyelids (unlike snakes that have an unblinking eye) and a flat tongue. The slow worm can also detach its tail like other lizards to avoid predation.

Their similarity to snakes has led to their historic persecution. Often known as ‘blind worms’ (likely due to the small size of the eyes), they were killed alongside adders and grass snakes with little apparent discretion between species. Even Shakespeare portrayed them as venomous serpents – the witches in MacBeth creating potions with the ‘blind-worm’s sting’.

In reality, the slow worm is placid in temperament and largely tolerant of human behaviour.

In this guide, we take a closer look at slow worms in the UK, revealing information on how to identify them, where they live and what they eat.

Interested in learning more about British wildlife? Check out our guides to snakes, frogs and toads, and deer.

Reptiles of the British Isles 

Discover the fascinating world of snakes, lizards and slow worms with BBC Countryfile Magazine’s guide to Britain’s six native reptiles.

• Reptile guide: snakes, lizards and slow worms

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What is a slow worm?

Perhaps the most remarkable attribute of a slow worm – Anguis fragilis – is its longevity. The oldest specimen recorded in captivity lived for at least 54 years, so an adult in the wild may be more than 25 years of age. Such a reptile would measure as much as 50cm long, with the grey-brown males fairly uniform in appearance but with blue spots that increase with age.

The females have dark brown sides and sometimes a thin line along the back. The juveniles, born in late summer, glow bronze as if freshly minted.

Slow worm behaviour

Unlike other British lizard species, the slow worm tends not to bask in direct sunlight, preferring instead to raise its body temperature by lying beneath objects or within rotting plant matter such as compost.

Slow worm diet

Slow worms feed on invertebrates such as slugs, snails, worms and spiders.

Slow worm habitat

They may be found beneath pieces of corrugated iron and can be encouraged into gardens by providing refugia for them.

They are liked by gardeners due to their fondness for slugs, although they are susceptible to predation from domestic cats.

As with other lizard species, the slow worm is reliant upon camouflage and will tend to remain still if discovered.

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