The slow worm (Anguis fragilis) is a legless lizard native to Europe, often mistaken for a snake or an earthworm. Despite its serpentine appearance, this reptile poses no threat to humans or household pets. It is a completely harmless species that lacks the physical means to cause injury, confirmed by its docile nature and lack of venom.
Classification and Appearance
The slow worm is a lizard, a fact often overlooked because it completely lacks limbs, resulting in a smooth, cylindrical, and snake-like body that can reach up to 50 centimeters in length. Unlike true snakes, the slow worm possesses several distinct lizard characteristics that betray its classification. It has movable eyelids, allowing it to blink, and small external ear openings, both features absent in snakes.
The scales of a slow worm are smooth and glossy, giving it a metallic sheen. They do not overlap in the same way as a snake’s scales, which aids its semi-burrowing lifestyle. When threatened, the slow worm can employ a defensive strategy known as autotomy, intentionally shedding its tail to distract a predator while the rest of the body escapes. Although the tail will partially regrow, it will not reach its original length, a classic lizard defense mechanism.
Assessing the Threat Level
Slow worms are non-venomous reptiles, producing no toxins that could be injected through a bite. Their diet consists primarily of soft-bodied invertebrates, such as slugs, snails, and earthworms. Securing this slippery prey requires only small, backward-curving teeth.
While a slow worm may attempt to bite if severely provoked, its jaw structure is weak and its teeth are minute. A bite from Anguis fragilis is entirely harmless and will rarely break the skin. Furthermore, slow worms are not known to carry diseases that pose a risk to humans or domestic animals. The greatest danger in an encounter is actually to the slow worm itself, as pets like cats frequently injure or kill them while playing.
Safe Interaction and Protection
If a slow worm is encountered in a garden or yard, the safest course of action is to leave it undisturbed so it can continue its beneficial role in the ecosystem. These reptiles are highly valued by gardeners because they naturally control populations of common pests like slugs and snails. They are often found hiding under discarded materials, like pieces of wood or corrugated iron, which they use to bask and warm their bodies.
The slow worm is a protected species in many parts of its range, including the UK, under the Wildlife and Countryside Act 1981. This protection makes it illegal to intentionally kill, injure, or sell the reptile. If a slow worm must be moved for its own safety, it should be handled gently and relocated only a short distance to a sheltered area with dense vegetation or a compost heap.