Slow worm or snake? Legless lizards are popping up in UK gardens this month - here's why that's a good thing

A surprise snake appearance while you’re pottering about in the garden is bound to give anyone a shock, but you should make sure to look twice - it might be a helpful slow worm.

UK wildlife channels on social media have been abuzz with supposed snake sightings in recent weeks, but most of the slithering reptiles have quickly been identified as slow worms - a much more common type of legless lizard. May is slow worm mating season, so you’re more likely than usual to see them out and about this month, according to the Young People’s Trust for the Environment.

However, these charming little creatures are quite unusual in their own right. But how can you tell them apart from snakes, and are they dangerous to you or your pets? Here’s everything you need to know about slow worms:

What is a slow worm?

Despite their serpentine appearance, slow worms are actually lizards - only without the legs. They are small reptiles, only growing up to 50cm long and weighing less than 100 grams as adults, according to the Wildlife Trust. Slow worms hibernate throughout the winter months, waking up around March. Similarly to many other lizards, they can also shed their tails when attacked by predators.

Although they typically live in tussocky grassland or around the edges of woodlands, they come into contact with humans quite frequently in gardens and allotments - as they enjoy hiding and hunting for insects around compost heaps. Insects are their preferred prey, and one study found they enjoy a hearty diet of slugs, snails, and caterpillars - making them useful allies for gardeners.

These long-lived reptiles are widespread across England, Wales, and Scotland, although they are absent from Northern Ireland and the Channel Islands. They are common across much of Europe, but their UK population has declined somewhat - largely due to habitat loss.

Are they dangerous to humans?

Not at all. They are very small and are prey to many larger species, so they typically prefer to avoid contact with humans at all, and usually try to stay hidden. Slow worms have no venom and can’t really bite hard enough to hurt you or your pets.

In fact, they rarely attempt to bite at all, the Natural History Museum says. Their usual defence mechanisms are to try and flee, or to defecate on you (their poo is apparently rather smelly). As a last resort, they will drop their tails to try and distract predators while they make their escape. It is safe to gently pick up and relocate a slow worm if it’s in harm’s way.

How can you tell the difference between slow worms and snakes?

Unlike snakes, slow worms (and most other lizards) have eyelids, so if you see it either blink or rest with its eyes closed, there’s a good chance you’ve spotted a slow worm. These reptiles are also much smaller than British snakes, and have smooth, golden-grey skin, according to the Wildlife Trusts.

Males are lighter in colour and sometimes sport tiny blue spots, while females are larger, with dark sides and a dark stripe down the back. Rather than having a more distinct head, the slow worm’s head is a similar width to its body - giving it a smooth-flowing, tubular appearance.

As the species can also shed their tails when attacked by predators, if you see what appears to be a small snake missing a lot of its tail (but still getting along okay), it’s probably a slow worm.

Are there any wild snakes that visit UK gardens?

The UK is home to several native snake species, including some which might stray into gardens from time to time. Grass snakes, although they prefer wetland and grassland habitats, are known to enjoy the warmth of compost bins in England and Wales, where they sometimes lay their eggs.

These snakes are greenish or yellowish in colour with dark markings on their sides, and are considerably bigger than slow worms, reaching up to 150cm and weighing in at 240g. However, they are also largely harmless to humans, and are non-venomous.

Very rarely, adders might also visit gardens - particularly if you live near their preferred woodland and heathland habitats. These greyish snakes (who have a distinctive black ‘zig zag’ pattern on their scales) enjoy basking on rocks or logs during warm weather, especially after waking up from their winter hibernation in March.

The adder is the UK’s only venomous snake. They will usually only bite when disturbed or threatened, so you should avoid getting too close if possible. If you are bitten, you should seek medical attention immediately. However, their venom is quite mild and not dangerous to most people, except for very young children, the elderly, and the immunocompromised.

It’s worth noting that all native snakes - and slow worms too - are legally protected in the UK under the Wildlife and Countryside Act 1981. It is an offence to kill, injure or take them from their habitats.