Often mistaken for a snake, our most commonly encountered reptile is in fact a lizard, the slow worm (Anguis fragilis). Snakes do not have eye lids, instead their eyes are covered in a transparent scale. Slow worms have eye lids and are therefore definitely lizards (despite the absence of legs!).
Identification
Slow worms are easy to distinguish from snakes due to their very shiny, almost polished appearance. They grow to 35-40cm long. Males are usually grey or brown with few markings. Although sometimes they will have blue spots on their sides. Males also have a broader head than the females. Females often have a black or dark line on their ventral side and darker flanks (similar to female common lizards). Juveniles are lighter in colour, with a silvery appearance. They also have black sides and a thin black ventral stripe. It is not possible to differentiate the sexes of juveniles. Melanistic (black) slow worms do occur, however, these specimens are rarer than in other reptiles.
It is very common for slow worms to lose their tail (giving rise to its name, fragilis, meaning fragile). The detached tail continues to wriggle which distracts the predator, allowing the slow worm to escape. The tails do grow back but always shorter than the original tail which when intact, is significantly longer than the slow worms body. Slow worms often therefore have a surprisingly subby appearance.
Habitat
Slow worms can be found in a range of habitats but are most likely to be encountered by humans while out doing the garden. Urban populations are common and populations can be found in surprisingly isolated or small areas of suitable habitat.
Slow worms are often found in gardens in piles of old grass cuttings, compost heaps, in log or brash piles, or road and rail embankments. Other preferred habitats include heaths, grasslands and at the bases of hedgerows. Like our other reptiles, slow worms are also found in open
woodland or woodland rides where sunlight is able to penetrate the canopy.
Slow worms are less likely to bask in the open than common lizards, instead preferring to hide in deeper vegetation or underneath warm flat rocks or in piles of garden rubbish exposed to the sun.
Distribution
Slow worms are common throughout the south of England with populations still common but more spread out further north and into Scotland. They are present in one location in Ireland. This is assumed to be an introduction and slow worms are not considered to be Irish natives.
Populations can be surprisingly high where favourable habitat is present. It is common to find multiple individuals hiding under refugia during surveys.
What Do Slow Worms Get Up to Throughout the Year?
September to March: Slow worms start heading to their hibernation sites from late September to October. During this time, they stay inactive underground in disused mammal burrows, compost heaps, or dense tussocky vegetation. Several individuals often hibernate together.
March: Slow worms emerge from hibernation in March. Males usually emerge slightly earlier than the females.
April to May: Mating occurs in April and May after emerging hibernation. During a rather aggressive copulation, the male bites the female on the head!
August to September: Pregnant females appear large and swollen. Live young in clutches of up to 25 are born in late summer. Groups of juveniles are often found clustered together under refugia during reptiles surveys.
Are Slow Worms Dangerous?
Despite looking superficially like a snake, slow worms are not snakes, not venomous and certainly pose no threat to humans or pets. On the contrary, they eat invertebrates such as slugs and caterpillars so are beneficial for reducing garden pests.
Take a look at the video below for some more interesting information on slow worms
Back to our Reptile Species Guides
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