Slow worm  (Anguis fragilis)

Protected in Britain under Schedule 5 of the Wildlife and Countryside Act (1981). Listed under Appendix III of the Bern Convention and classified as a Priority Species under the UK Biodiversity Action Plan (UKBAP) (3).

The slow worm, a legless lizard, was once thought to be a serpent and is often mistaken for a snake. There are certain features that separate the slow worm from snakes, however, including the presence of an eye lid, which earned the species the alternative name of 'blind worm' (2). This species is the most commonly seen reptile in Britain (4). Adults have a smooth, shiny appearance, and a grey or bluish belly. Males and females are different in appearance; females are brown, copper coloured or red on the back, with brown or black sides, often with lighter iridescent flecks. In many individuals there is a dark stripe passing along the middle of the back and stripes running along the sides of the body. Males vary in colour, they may be greyish, brown, coppery or reddish-brown, and typically do not have stripes; furthermore, they have broader and longer heads (2). Occasionally, individuals may have blue spots, a feature that is more common amongst males than females. In juvenile slow worms, the back is iridescent silver, gold, bronze or copper and the sides are brown or black (2).

Widespread throughout Britain, but most common in the south and east of England (2). This species also has a broad distribution in continental Europe, where it is found from Scandinavia south to northern Spain and Portugal, and eastwards to southwest Asia and western Siberia (2).

You can view distribution information for this species at the National Biodiversity Network Gateway.

The slow worm is found in a wide range of open habitats, it tends to take refuge under stones, planks of wood or sheets of corrugated iron in the sun, rather than basking. They are commonly found in gardens and compost heaps, where food is plentiful and the rotting plant material creates warm conditions (4).

Although slow worms, like snakes, are often feared and persecuted, they should be welcome visitors to gardens as they feed largely on slugs, snails and other slow-moving garden pests (5). The Latin name Anguis fragilis means 'fragile snake' (2), and refers to the ability of this lizard to shed its tail when seized; the tail may continue to wriggle after being shed, and can distract predators while the slow worm escapes (5). A new tail begins to regenerate after a couple of weeks (2). Although this species is widespread, it is rather secretive, and is consequently Britain's least understood reptile (2).

Slow worms emerge from hibernation in March, and courtship tends to take place between mid-May and late June; at this time males become aggressive towards each other (2). During courtship, a male takes hold of a female by biting her head or neck, and they intertwine their bodies. Courtship may last for as long as 10 hours before copulation occurs (2). Most females tend to mate once every two years in Britain; an average of 8 live young are usually born from mid-August to mid-September. The young slow worms are initially encased in the egg membrane, they measure from 70-100 mm in length, and will be fully grown after 6-8 years, becoming sexually mature by 3 or 4 years in males and 4 or 5 years in females (2). This species is relatively long-lived; one specimen lived for 54 years (5). The skin is shed at intervals throughout the life span (2).

This species is not currently threatened in Britain.

The slow worm is protected under Schedule 5 of the Wildlife and Countryside Act (1981). Under this act, it is illegal to kill, injure, and sell this species (3).

View information on this species at the UNEP World Conservation Monitoring Centre.

There may be further information about this species available via the National Biodiversity Network Gateway.

For more on this species and other reptiles and amphibians of the UK see:

• The Herpetological Conservation Trust:
  http://www.herpconstrust.org.uk/index.php

For more information on the slow worm, visit:

• BBC Wildlife Finder: 
  http://www.bbc.co.uk/nature/species/Anguis_fragilis