Reptiles
Slow Worm
Anguis fragilis · also called slowworm, blindworm, deaf adder
The smooth bronze creature that turns up under a compost heap or a paving slab in a European garden, looking like a small polished snake, is a slow worm. It is not a snake and not a worm. It is a lizard that has given up its legs, and it may be older than the gardener who found it.
Overview
Anguis fragilis is a legless lizard, 40 to 50 cm long, found across most of Europe in rough grassland, hedgerows, and gardens. It keeps the lizard features a snake lacks: blinking eyelids, ear openings, an only slightly notched tongue, and a droppable, regrowing tail. It eats slugs and earthworms.
A very long life
Slow worms are among the longest-lived lizards. Wild adults often reach 20 to 30 years, and a captive male in Copenhagen lived to at least 54.
Underground and live-bearing
It spends most of its time buried or hidden under logs, stones, and metal sheets, and it gives birth to live young in late summer rather than laying eggs.
Status
Least Concern and widespread, a welcome slug-eater in gardens and legally protected in Britain, though it declines where scrubby ground is built on and where cats hunt it.
Slow Worm: common questions
Is a slow worm a snake?
No. It is a lizard that has lost its legs, a body plan that has evolved many times among lizards because it suits a life of burrowing and moving through dense vegetation and leaf litter. The differences from a snake are clear once you know them. A slow worm can close its eyes and blink, which no snake can do, it has small ear openings behind the eyes, its tongue is broad and only slightly notched rather than deeply forked, and it can shed and regrow its tail. It is also much smaller and more delicate than the snakes it shares its range with, growing to around 40 to 50 centimetres, and it has a smooth, uniform, almost polished look.
Why is it called a slow worm or a blindworm if it is neither slow nor blind?
The names are old and inaccurate. It is not a worm at all, it is not blind, since it has functioning lidded eyes, and it is not especially slow; it can move at a fair pace when it needs to. Blindworm is thought to come from an Old English word meaning something like blinding or striking, perhaps a misunderstanding, rather than from a lack of sight, and slow may derive from a word for a slug, its main prey, or simply describe its unhurried habits. Deaf adder is another old country name, wrong on both counts, since it can hear and is not an adder or venomous in any way.
How long do slow worms really live?
Longer than almost any other lizard. In the wild, where predators, cats, road traffic, and cold winters take a toll, a slow worm that survives to adulthood often lives 20 to 30 years, and mark-recapture studies have followed individuals for two decades or more. In captivity, protected from those hazards, the record is remarkable, since a male slow worm at Copenhagen Zoo is documented to have lived to at least 54 years old. For comparison, most small lizards live only a few years. The slow, cool, low-energy life of a burrowing invertebrate-eater seems to go with a very long potential lifespan.
What should I do if I find a slow worm in my garden?
Leave it alone and be glad of it. Slow worms eat large numbers of slugs and snails and are completely harmless to people, pets, plants, and produce. If you find one in a compost heap or under a paving slab, cover it back up gently and try not to disturb that spot. If you must move one, for instance out of the way of digging, pick it up carefully with two hands supporting the body and never by the tail, which it may drop. In Britain it is a protected species, so deliberately killing or harming one is against the law, and keeping the garden a little wild, with log piles and long grass, will encourage it to stay.