Slow Worm

A slow worm is not a snake and not a worm. It is a legless lizard, Anguis fragilis, native to Britain and much of Europe. It belongs to the same lizard order as bearded dragons and monitors, even though it has no visible legs.

This animal has eyelids that blink. It has small external ear openings.

It can also drop its tail and partly regrow it. No snake can do any of these three things.

This guide covers what separates it from a snake, the recent split of the genus Anguis into several species, how long individuals live, what they eat, and how they reproduce. It also covers the legal protection behind British populations. Because the species is wild and protected, the sections below describe wild biology and what a licensed zoo or nature center provides, not a home setup.

Slow Worm vs Snake: How to Tell the Difference

The fastest way to answer is a slow worm a snake is to check the eyes and ears. This lizard has movable eyelids and blinks normally. A snake’s eyes are covered by a fixed clear scale and never close.

It also has a small visible ear opening on each side of its head. No snake has this feature. It moves with a straighter, more deliberate glide than the side to side whip of a snake.

Its scales are small, smooth, and cylindrical. A snake’s belly scales are broad and overlapping, built for gripping the ground.

If threatened, it can shed part of its tail through autotomy. The replacement tail grows back shorter and blunter, another trait most snakes lack.

The name slow worm lizard is more accurate than either “worm” or “snake.” It moves slowly compared with a true snake, but it is built like a lizard in every anatomical sense.

The Anguis Species Complex

Field guides once described a single wide ranging species. A 2010 study in Molecular Phylogenetics and Evolution found four deeply divergent DNA lineages that each rank as a species. The common form, Anguis fragilis in the strict sense, covers western and central Europe and the northwestern Balkans, including the British Isles.

The eastern relative, Anguis colchica, was once treated as a subspecies of fragilis. It is now recognized as a full species. Its range runs from the eastern Czech Republic to northern Iran.

Anguis graeca lives in the southern Balkans and Anguis cephallonica in the Peloponnese of Greece. Italian populations have since been separated as Anguis veronensis.

All of them look extremely similar externally. Any individual found in the UK is identified as Anguis fragilis by range, not appearance.

What Slow Worms Eat

This species’ diet centers on slugs and earthworms, according to Animal Diversity Web. That makes it one of the few native predators that specializes in the soft bodied prey gardeners consider pests. It hunts mostly by scent and touch rather than sight.

It pushes its blunt snout through leaf litter, compost, and loose soil to find prey. Because slugs and worms are slow and soft bodied, it does not need speed or powerful jaws. Its small teeth grip prey rather than tear it, and it swallows food whole after a short struggle.

An individual living in a compost heap or vegetable bed provides free pest control. This is one reason conservation groups ask gardeners to leave compost piles and log piles undisturbed.

Breeding and Reproduction

This lizard is ovoviviparous. The eggs develop and hatch inside the mother’s body. She gives birth to fully formed live young rather than laying eggs.

A female typically breeds only every other year. Carrying and producing young costs a great deal of energy. Gestation lasts roughly 3 to 5 months, depending on temperature and food that season.

A single litter usually holds 3 to 20 young. Most births happen from August through September in the UK. Newborns measure only a few centimeters and get no parental care.

Sexual maturity arrives at around 3 to 4 years old. That is slow compared with many small lizards. It is part of why local populations recover gradually after declines.

Males and females differ in color. Females usually show a dark stripe down the back and along the sides. Males tend to be a more uniform bronze or gray, and older males sometimes show small blue spots on the back.

Mating involves the male gripping the female’s neck or head with his jaws. This can leave faint bite marks. The marks are not harmful and heal quickly.

Lifespan and Size

This species is unusually long lived for a small lizard. The AnAge longevity database lists a wild lifespan of around 30 years, which it flags as anecdotal since few detailed field studies exist. Its captive record of 54 years is firmer, and it makes this one of the longest lived lizards known anywhere.

Adults reach a snout to vent length of about 120 to 200 millimeters, roughly 4.7 to 7.9 inches. That figure does not include the tail. Total length with an intact tail is noticeably longer, though exact figures vary between individuals.

A regrown tail after autotomy is always shorter and blunter than the original. Adult mass ranges from about 20 to 100 grams. A full grown adult is lighter than most people expect from its length.

Habitat: Where This Lizard Lives

In the wild, this animal spends most of its life underground or under surface cover. It rarely sits out in the open. It favors damp, cool microhabitats such as compost heaps, log piles, and grass tussocks.

Its range spans woodland, grassland, heath, and gardens across western and central Europe. A licensed zoo, nature center, or school holding one under an educational or conservation license copies this setup. Staff provide a deep, moisture retentive substrate such as leaf litter over soil, several stacked hides, live plants or moss, and a shallow water dish.

This species is secretive by nature, so enclosure design favors places to disappear into over open floor space. Overhead cover matters more than height. General background on how lizards use their living space appears in this site’s overview of the different types of lizards and their habitat needs.

Thermoregulation: Heating and Lighting Needs

This lizard regulates its body temperature by moving in and out of cover. It does not bask in the open the way many pet lizards do. In the wild it warms itself near a sun warmed log or stone, then retreats into cool, damp soil once it has absorbed enough heat.

This strategy suits an animal with thin skin that loses moisture quickly in direct sun. Licensed collections generally provide a gentle background temperature gradient rather than an intense basking spot. This often falls in the range of 18 to 24 Celsius, or 64 to 75 Fahrenheit, with a cooler, moister zone always available.

Ultraviolet lighting is used at low to moderate levels in most professional setups. That reflects an animal that spends much of its life shielded from direct sun. Because the species is not sold or kept privately in the UK, these details describe institutional practice, not home equipment.

Health and Threats

The biggest cause of injury and death for this species is not disease. It is predation and human activity. Domestic cats are a major predator in gardens.

Lawnmowers, strimmers, and garden forks cause serious injuries too. Individuals often hide under grass clippings, compost, or debris. Disturbing this cover without warning is a common cause of accidental harm.

Autotomy, the ability to drop the tail when grabbed, is a normal defense rather than a health problem. It still costs the animal stored energy. The replacement tail never fully matches the original in length or color.

Like other reptiles, this species can carry internal parasites. It is also susceptible to fungal and viral pathogens documented in UK reptile populations. Conservationists ask people not to move individuals between sites, since this can spread disease between otherwise isolated populations.

Anyone who finds an injured animal should contact a local wildlife rescue or an exotic capable veterinarian. Home treatment is not recommended. Further general reptile health guidance appears in this site’s lizard health guide.

Care and the Law

This species is wild and protected, not a legal pet in the UK. Anguis fragilis is listed on Schedule 5 of the Wildlife and Countryside Act 1981, as amended.

The schedule lists it under section 9(5), which bans selling, offering for sale or advertising one. Natural Resources Wales confirms that intentionally killing or injuring one is also an offense.

It is not one of the fully protected reptiles. The sand lizard, by contrast, is also protected against disturbance and damage to its shelters under sections 9(4)(b) and (c). Its protection is narrower, but it still rules out any trade.

This protection applies whether the animal turns up in a garden, a nature reserve, or anywhere else in its native range. Licenses to handle, survey, or hold individuals exist only for scientific, research, educational, or conservation purposes. In Wales these are administered by Natural Resources Wales, with equivalent bodies covering England and Scotland, and licenses are specifically not granted to support development projects.

A welfare minded approach means leaving wild individuals where they are found. Report sightings to a local wildlife trust or biological records center if asked. Never collect one to keep at home.

Readers interested in the wider family this animal belongs to can compare it with relatives on this site’s legless lizard overview, and the related sheltopusik and glass lizard pages, without repeating identification details covered there.

Cost: Why It Is Not for Sale

There is no legitimate purchase price for this animal. Schedule 5 protection makes selling one a criminal offense in the UK. No reputable source will ever list one for sale.

Anyone offering one for money in the UK, wild caught or claimed as captive bred, should be treated as a red flag rather than a bargain. Report such listings to the relevant wildlife enforcement authority.

The only costs genuinely tied to this animal are indirect. A garden owner might spend a little on log piles, compost bins, or leaving an unmown corner. This helps it and other garden wildlife, and it costs far less than any pet setup.

Licensed institutions bear the real husbandry costs of enclosure setup and staff time. None of those costs are passed on to the public through any legal transaction.

Encouraging Them in a Garden

This species relies on cover rather than open basking spots. The single most useful thing a gardener can do is leave places for it to hide. Compost heaps, log piles, loosely stacked stones, and an unmown strip of long grass all provide the damp, sheltered space it needs.

This kind of cover lets it hunt slugs and stay cool at the same time. Check a compost heap carefully by hand before turning it. Avoid chemical slug pellets, which remove the food supply and can poison predators indirectly.

Mow paths around long grass in summer rather than through it. For background on what garden lizards more broadly eat, see this site’s guide to what lizards eat. For how a long lived species like this compares with other lizards, this site’s overview of lizard lifespan places its 30 year average and 54 year captive record in wider context.

Frequently Asked Questions

Is a slow worm a snake?

No. It is a legless lizard in the family Anguidae, not a snake. It has movable eyelids, small external ear openings, and a tail it can shed and partly regrow, none of which any snake can do.

Are slow worms dangerous or venomous?

They have no venom and pose no danger to people or pets. A cornered individual may bite in self defense, but the bite rarely breaks skin. Its main defense is fleeing into cover or dropping the tail.

Can you keep a slow worm as a pet in the UK?

No. Anguis fragilis is protected under Schedule 5 of the Wildlife and Countryside Act 1981. Only licensed zoos, schools, and conservation projects may hold individuals, and only for research, education, or conservation purposes.

What is the difference between Anguis fragilis and Anguis colchica?

Anguis fragilis, the common form found in the UK, and Anguis colchica, its eastern relative, were once treated as one species. A 2010 genetic study split them into full species with different ranges. Fragilis covers western and central Europe, while colchica runs from the eastern Czech Republic to northern Iran, even though the two look almost identical.

Do slow worms help control slugs in gardens?

Yes. Slugs and earthworms make up most of their diet, so a garden with a resident population gets some natural slug control without pesticides. This is a key reason wildlife groups encourage gardeners to protect compost heaps and log piles.

How long do slow worms live compared to other lizards?

This species is exceptionally long lived, with wild lifespans reported at around 30 years. A documented captive record of 54 years puts it among the longest lived lizard species known. That is well beyond the lifespan of most small lizards, many of which live only a few years in the wild.