Slow worm (Anguis fragilis)

Also known as: Blind worm
KingdomAnimalia
PhylumChordata
ClassReptilia
OrderSquamata
FamilyAnguidae
GenusAnguis (1)
SizeAdult length: up to 40 cm (2)

The slow worm is not currently classified on the IUCN Red List.

Being a legless lizard, the slow worm (Anguis fragilis) is often mistaken for a snake. However, there are certain features that separate the slow worm from snakes, including the presence of eyelids and ear openings (2).

This species can be locally abundant and, in Britain for instance, it is likely to be the most commonly seen reptile (3). Adults have a smooth, shiny appearance (4), and a grey or bluish belly. The male and female differ in appearance; the female is usually 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. The male varies in colour, being greyish, brown, or coppery- or reddish-brown, typically without stripes. The male usually has a broader, longer head than the female (2).

Occasionally, individuals may have blue spots, a feature that is more common among males than females. In juvenile slow worms, the back is iridescent silver, gold, bronze or copper and the sides are brown or black (2).

The slow worm is widely distributed throughout Britain and continental Europe, from Scandinavia south to northern Spain and Portugal. It also occurs in extreme northern Africa, eastwards to southwest Asia and western Siberia (2) (4).

The slow worm is found in a wide range of open habitats and tends to take refuge under stones, planks of wood or sheets of corrugated iron in the sun, rather than basking. It is commonly found in gardens and compost heaps, where food is plentiful and the rotting plant material creates warm conditions (3).

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 scientific 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 (2)

The slow worm usually emerges from hibernation in March, and courtship tends to take place between mid-May and late June, at which time males typically become aggressive towards each other (2). During courtship, a male takes hold of the female by biting her head or neck, and the bodies of the two lizards will become intertwined. Courtship may last for as long as 10 hours before copulation occurs (2).

Depending on the local climate, the female slow worm will mate annually or once every two years. The slow worm is ovoviviparous, and instead of laying eggs, the female gives birth to an average of eight live young between mid-August and mid-September. The young slow worms are initially encased in the egg membrane and measure from 70 to 100 millimetres in length. It takes between six and eight years for the slow worm to become fully grown, although the male reaches sexual maturity at three or four years of age. The female becomes sexually mature at four or five years of age (2).

This species is relatively long-lived, with one specimen known to have lived for 54 years (5). The skin of the slow worm is shed at intervals throughout its life (2).

Due to its large geographical distribution and the wide range of habitats in which it occurs, this species does not currently appear to be globally threatened.

In the United Kingdom, 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 individuals of this species.

The slow worm is classified as a ‘Priority Species’ under the UK Biodiversity Action Plan (UKBAP), as it is itself a declining species, as well as a good `indicator` species for a declining taxonomic group (6). The slow worm is also listed under Appendix III of the Bern Convention (7).

For more on this species and other reptiles and amphibians found in the UK, see:

For more information on the slow worm, visit:

Authenticated (29/10/11) by Olivier S.G. Pauwels, Research Associate at the Royal Belgian Institute for Natural Sciences, Brussels, Belgium.
http://www.pauwelsolivier.com/

  1. UNEP-WCMC (March, 2012)
    http://www.unep-wcmc.org/
  2. Beebee, T. & Griffiths, R. (2000) The New Naturalist: Amphibians and Reptiles - A Natural History of the British Herpetofauna. HarperCollins Publishers, London.
  3. The Herpetological Conservation Trust - Slow worm fact sheet (March, 2012)
    http://www.herpconstrust.org.uk/animals/slow_worm.htm
  4. The Reptile Database (October, 2011)
    http://reptile-database.reptarium.cz/species?genus=Anguis&species=fragilis&search_param=%28%28taxon%3D%27Anguidae%27%29%29
  5. Buczacki, S. (2002) Fauna Britannica. Hamlyn, London.
  6. Joint Nature Conservation Committee (June, 2009)
    http://www.jncc.gov.uk/page-3408
  7. Council of Europe: Bern Convention (October, 2011)
    http://conventions.coe.int/Treaty/EN/Treaties/Html/104.htm