What’s cold-blooded, long, smooth and scaly, slithers along the ground, scents the air with its tongue, eats slugs, earthworms and bugs and can shed its tail to escape an attacker?
If you said, “a snake”, you’d be wrong. The last bit gives it away – snakes can’t shed their rear ends, but slow worms can.
What is a slow worm?
A slow worm is not a worm or a snake – it's actually a legless lizard. Snakes belong to the family of Squamata, suborder Serpentes. Slow worms are classed under the suborder Anguimorpha, which makes them very distant cousins of snakes but certainly not the same, despite outward appearances.
Slow worms are found in most of Europe and just into western Asia. They live in damp places in heathland and along the edges of woodland. In gardens they can often be found hanging around a compost heap, which is an easy place to go stalking their prey.
Their unusual name could be considered a straightforward description as they have a worm-like body and they don’t move very fast. But there is the Old English name for them slāwyrm coming from Old German slā, meaning snake and OE wyrm, meaning crawling animal.
How big are slow worms?
From tip of nose to tip of tail they can be between 16 and 18 inches long (40-45cm).
What do slow worms look like?
Their head merges into their body with no sign of a neck and, although it can be detached, the tail likewise just grows out of the torso with no visible join.
They have mottled brown and gold skin made up of scales that don’t overlap, adding to the smooth, sleek appearance. This characteristic helps slow worms in their tendency to burrow, as there are no scales to catch on things if they back up. Bony deposits form plates under their skin, which makes them a little stiff of movement, lacking the fluidity of a snake.
The males are lighter in colour and sometimes have blue spots; the females are the bigger of the two and darker, with a dark stripe along their backs.
A slow worm that has lost its tail will grow back another that is not as long as the original – so if you see a stumpy one you’ll know it has experienced some trauma in its life.
How do slow worms differ from snakes?
Slow worms have a notched tongue where each ‘fork’ is quite short and thick. Snakes have much longer, slimmer forks and the tongue reaches out much further.
A snake has no eyelids, so cannot blink. Its eyes are protected by a fixed type of scale that acts like a contact lens to keep out dust and prevent damage from scratching. Consequently, it sleeps with its eyes open. A slow worm can get some shuteye because it has a flexible eyelid and it blinks to keep its eyeball clean.
Both animals shed their skins, but snakes do it all of a piece, whereas slow worms drop little patches at a time. So if you find small deposits of reptile skin in the garden it’s most likely to have come from a growing slow worm working its way out of its old coat.
Do slow worms hibernate?
In winter, both animals brumate, which is the snake/slow worm equivalent of hibernation and doesn’t involve going completely comatose in the cold. But their choice of accommodation varies, from snakes hiding in cracks and crevices to slow worms burrowing underground.
How do slow worms defend themselves?
Slow worms have a couple of unexpected tricks if they are attempting to escape a predator. They excrete a noxious-smelling poo and, if that’s not enough to put off the hunter, they drop their tail. This will thrash about on its own for a short while, confusing the attacker and allowing the slow worm to slip away.
Snakes hiss and bite, and some species can emit a smelly musk. Being the quicker of the two animals snakes also often rely on a speedy exit to evade predators.
Slow worms can also bite but they reserve that activity for mating. They grasp the female in an amorous nip round the head and then the two entwine for a lengthy copulation.
