Slow WormAnguis fragilisWhere and when to see them

The slow worm is a legless lizard, not a snake, and one of Scotland's native reptiles. Its smooth, glossy body is well suited to moving through grass, leaf litter and loose soil. Because it spends much of its time concealed, it can be present in gardens and rough ground without being noticed. Habitat tidying, road mortality and attacks by domestic cats can affect local populations, even where apparently suitable green space remains.

Size

30-45 cm total length

Weight

20-100 g

Lifespan

Not reliably established

Status

Least Concern

Slow worms are secretive and often warm themselves beneath vegetation or other cover rather than basking in the open. They emerge to forage when conditions are mild and humid, sometimes around dusk. During cold months they become inactive in sheltered underground spaces, occasionally sharing refuges. Females retain developing young internally and give birth to live offspring, usually in late summer or early autumn in Britain. They are long-lived, potentially reaching 30 years in the wild and even longer in captivity, indicating a slow life history strategy. When threatened, they may freeze or perform a 'tail shedding' (autotomy) as a distraction, regenerating a shorter, blunt tail over time. Slow worms are generally docile, preferring to escape into cover rather than biting when handled, though this should be avoided.

• Slow worms can blink because they have movable eyelids.
• A shed tail does not regrow to its original full form.
• Females give birth to live young rather than laying exposed eggs.
• Youngsters often have golden bodies with a dark line along the back.

April to September is a useful Scottish search window, adjusted for local temperature and altitude. Mild, humid weather is often more productive than hot sunshine. Spring activity and late-summer births are distinct events within a relatively short northern active season. Early mornings or late afternoons after a period of rain can be particularly productive for sightings. Observing during cooler, overcast days can also increase chances, as they are less likely to overheat while foraging. Activity typically peaks when ambient temperatures are between 15-20°C, and they become less active above 25°C.

Rough grassland, heathland margins, woodland edges, gardens and vegetated banks can all support slow worms. Suitable sites combine warm patches, moist feeding areas and secure cover. In Scotland, sheltered lowland and coastal situations may offer better conditions than exposed uplands. They favour south-facing banks and slopes for thermal regulation, and can often be found near old stone walls or rock piles. Given their secretive nature, healthy populations can persist in surprisingly small, undisturbed pockets within developed areas. In Scotland, they are most often encountered in coastal machair, lowland glens, and woodland clearings.

Slow worms mainly eat slugs, earthworms and other small, soft-bodied invertebrates. Small snails and arthropods may also be taken. Their prey choices make damp, structurally varied vegetation valuable, especially where pesticide use and intensive mowing have not depleted invertebrate life. Their preference for slugs makes them valuable natural pest controllers in gardens and agricultural settings. They have a relatively slow metabolism, allowing them to go extended periods between meals. Young slow worms primarily feed on smaller invertebrates such as spiderlings and tiny slugs.

Common name

Slow Worm

Scientific name

Anguis fragilis

Animal group

Reptiles

Size

30-45 cm total length

Weight

20-100 g

Lifespan

Not reliably established

Status

Least Concern

Identification

Unlike snakes, slow worms have movable eyelids, a blunt head with little neck distinction and a tail that can be shed, while their scales give a uniformly polished appearance. Unlike snakes, their scales are smooth and non-overlapping, giving them a glossy appearance. Adult males are typically grey or bronze and may have blue spots along their flanks, while females are usually brown or copper with dark sides and a distinct dark stripe down their back. Juveniles often exhibit striking gold or silver coloration with a prominent dark dorsal stripe and dark belly.