Slow Worms in the UK

The slow worm (Anguis fragilis) is a secretive and misunderstood reptile native to the UK. Despite often being mistaken for a snake, it is actually a legless lizard—distinguished by several key features such as the ability to blink and shed its tail. Found in gardens, grasslands and heathlands across the country, the slow worm plays a vital role in the ecosystem by keeping slug and insect populations in check.

This blog post provides a detailed guide to slow worms in the UK, including how to identify them, their behaviour, habitat, diet, life cycle, threats, conservation status, and tips for spotting them in the wild.

Identification and Appearance

Slow worms have smooth, shiny bodies and can be surprisingly variable in colour. Their appearance often leads to confusion with snakes, especially juvenile grass snakes or adders.

Key features

• Size: Adults grow to 30–50 cm in length; females are usually larger than males.
• Colour: Varies from golden brown to grey or copper. Females often have a dark stripe down the back and flanks; males may be more uniform in colour.
• Eyes: Unlike snakes, slow worms have eyelids and can blink.
• Tail: Can be shed as a defence mechanism—this is known as autotomy.
• Tongue: Not forked like a snake’s.

Their scales give them a smooth, polished appearance, and they move with a gentle, gliding motion, slower than most snakes.

Distribution and Habitat

Slow worms are widespread across the UK, including England, Wales and much of Scotland. They are also found in parts of Ireland and on some offshore islands.

Preferred habitats

• Grasslands and meadows
• Heathland and scrub
• Woodland edges and clearings
• Gardens, compost heaps and allotments
• Railway embankments and roadside verges

They prefer habitats with plenty of cover, warmth, and access to invertebrate prey. Gardens with log piles, rocks and compost heaps can provide ideal refuges.

Behaviour and Lifestyle

Slow worms are largely crepuscular and nocturnal, avoiding the heat of the day. They spend much of their time hidden under rocks, logs or vegetation.

Key behaviours

• Basking: May bask under objects like corrugated sheets or garden mats, which provide warmth without exposure.
• Burrowing: Capable of burrowing into loose soil or leaf litter.
• Tail shedding: When threatened, they may shed part of their tail to escape predators; the tail often regrows, though not to its original length.

Slow worms hibernate from around October to March, often communally in frost-free shelters like underground crevices, compost heaps, or tree root systems.

Diet and Feeding

Slow worms are insectivores with a preference for soft-bodied invertebrates.

Common food sources

• Slugs (especially keeled and juvenile slugs)
• Earthworms
• Beetles
• Woodlice
• Caterpillars and larvae

They hunt primarily by smell, using their tongue to sample chemical signals in the environment. Their slow movement and camouflage help them ambush prey.

Reproduction and Life Cycle

Slow worms are viviparous—meaning they give birth to live young, a rarity among reptiles.

Breeding facts

• Mating season: May to June
• Gestation: Around 3 months
• Birth: July to September
• Litter size: Typically 5 to 15 young
• Newborns: Around 7–10 cm long, often with shiny black or gold skin

Young slow worms are independent from birth and must find their own food and shelter.

Predators and Threats

Slow worms face natural and human-related threats, despite their secretive lifestyle.

Natural predators

• Hedgehogs
• Birds of prey (e.g. kestrels)
• Foxes
• Cats (a major predator in gardens)
• Larger snakes

Human-related threats

• Habitat loss and fragmentation
• Garden machinery and digging
• Road mortality
• Illegal collection for the pet trade (now rare but historically damaging)

Slow worms are highly vulnerable when basking or during mating season when they are more exposed.

Conservation Status

Slow worms are legally protected in the UK under the Wildlife and Countryside Act 1981.

Legal protection

• It is illegal to intentionally kill, injure, or sell slow worms.
• Their habitats are also safeguarded in many nature reserves and development plans.
• Conservation efforts focus on habitat preservation and public education.

Although still fairly widespread, local populations can suffer from poor land management and urbanisation.

Slow Worms versus Snakes

Understanding the difference between slow worms and snakes is essential for their protection.

Differences

• Eyelids: Slow worms can blink; snakes cannot.
• Tail: Slow worms have a long tail that makes up nearly half their body length.
• Movement: Slower, less fluid than snakes.
• Shedding: Slow worms shed in patches; snakes shed their skin in one piece.

Their calm, non-aggressive nature makes them excellent garden allies.

Importance in the Ecosystem

Slow worms are beneficial to gardeners and play a valuable role in controlling pest populations.

Ecological roles

• Natural slug control, reducing damage to plants and crops
• Part of the food chain, supporting predators such as birds and mammals
• Indicators of healthy ecosystems with good structural habitat diversity

Their presence is often a sign of well-connected green spaces and managed gardens.

Observing Slow Worms in the Wild

Though shy, slow worms can be encountered in gardens and countryside if you know where to look.

Tips for spotting slow worms

• Carefully lift warm items like paving slabs, garden mats, or corrugated metal sheets in sunny areas
• Check compost heaps or log piles in quiet corners
• Visit nature reserves with known populations, especially in late spring or summer

Avoid handling slow worms—they may shed their tail when stressed. Leave them undisturbed and ensure cover is replaced after looking.

Conclusion

Slow worms are fascinating and often overlooked members of the UK’s reptile family. Neither worm nor snake, they are gentle, helpful creatures deserving of protection and appreciation. As gardens, green corridors and wild spaces become increasingly vital refuges, supporting slow worms contributes to local biodiversity and healthy ecosystems.

By creating wildlife-friendly habitats and spreading awareness, we can help ensure that these charming legless lizards continue to thrive across Britain.