Where Do Slow Worms Live? Gardens, Heaths and Compost

Where do slow worms live in Europe?

The slow worm (Anguis fragilis) ranges from northern Spain and Portugal across France, the Low Countries, Germany, Switzerland and Austria to the western Balkans. In the north it lives in Great Britain, Denmark, the far south of Norway and southern and central Sweden. It is missing from southern Iberia, most Mediterranean islands and northern Scandinavia.

Since about 2010, scientists have recognized several separate slow worm species that were once included in Anguis fragilis. The eastern slow worm (Anguis colchica) replaces it from eastern Europe and southern Finland to the Caucasus and northern Iran, while other close relatives live in Italy, Greece and the Peloponnese. The western and eastern species meet in a band running roughly through Poland, the Czech Republic, Slovakia, Hungary and Romania.

Slow worms are not only lowland animals. In the Swiss Alps they have been found up to about 2,100 m (6,900 ft), and in the Austrian Alps up to about 2,400 m (7,900 ft), above the tree line.

Where do slow worms live in Britain and Ireland?

In Britain, slow worms are widespread across England, Wales and much of Scotland, though records become more scattered in the far north. They also live on the Channel Islands of Jersey, Guernsey, Herm and Jethou. Because they are so secretive, they are often more common in an area than people realize.

Ireland is different. Slow worms are naturally absent there, like most reptiles; the island’s only native land reptile is the common lizard. A small population lives in the Burren in County Clare, extending into neighboring Galway, but it is believed to have been introduced by people in the 20th century. Our guide to animals of Ireland explains why so few reptiles reached the island.

Which habitats do slow worms prefer?

Slow worms are adaptable and use many kinds of habitat, as long as three things are present: dense, low vegetation for cover, some moisture in the soil, and sunny spots where they can warm up. They are less dependent on heat than most European reptiles, which is why they can live in fairly cool, damp places.

They can even live in dense conifer plantations if there are small sunny gaps. Because their needs are broad, slow worms often share habitats with other reptiles: with common lizards and adders in damper places and with smooth snakes and sand lizards on dry heaths. Compare where adders live, which need much more open, sunny habitat.

Slow worms in gardens and compost heaps

In Britain, gardens and allotments are among the best places to find slow worms, especially in older, slightly untidy gardens near grassland, woodland or railway lines. Compost heaps are particularly attractive. Decomposing material keeps them warm and damp, and they are full of slugs, worms and other small invertebrates for the lizards to eat.

Pregnant females need more warmth than other slow worms and are the ones most likely to be seen basking in the open in summer. Slow worms also shelter under paving slabs, sheds, decking, wood piles and stone walls.

Garden life has its risks. Domestic cats catch many slow worms, and garden chemicals, mowing and strimming of long grass, and the tidying away of log and leaf piles can all harm them. Gardeners who turn compost or move wood piles carefully, especially in winter when the reptiles are dormant, help them survive.

Hiding places: logs, stones and sheets

Slow worms rarely bask in the open like other lizards. Instead they lie under objects that are warmed by the sun, absorbing heat from above while staying hidden. Typical hiding places include:

• Flat stones, logs and fallen branches
• Sheets of corrugated metal, roofing felt or old carpet
• Holes in the ground, rock crevices and the spaces among tree roots
• Moss cushions, leaf piles, grass tussocks and compost heaps

Ecologists take advantage of this habit. To survey reptiles, they lay out squares of roofing felt or corrugated metal, called refugia, and check under them on warm mornings. Several slow worms often share a good sheet.

Slow worms are most active at the surface early in the morning, in the evening and on mild, damp days, especially after rain, when slugs and worms are moving about. In the middle of a hot, dry day they usually stay hidden.

Where do slow worms go in winter?

Slow worms hibernate for about half the year. In central Europe and Britain, most go underground during October and come out again in March or April, depending on the weather.

They choose frost-free sites such as rodent burrows, root holes, rock crevices, rotten tree stumps and deep compost or leaf piles, and they may dig their own tunnels, sealing the entrance with moss or soil. Hibernation is often communal: groups of about 5–30 slow worms are typical, and more than 100 have been found together. Older animals tend to lie deeper, and they sometimes share their winter quarters with other reptiles, including snakes. See do snakes hibernate? for how other reptiles cope with winter.