British Wildlife of the Week

Slow-worm

If you were asked to think of a legless reptile, your mind would probably conjure up images of some kind of snake. But leglessness has also evolved in lizards – several times over, in fact. The biggest lizard family – the skinks – includes numerous groups that have on multiple, separate occasions lost their limbs. Here in the UK (which, it has to be said, is a very reptile-deficient country), we have just one legless lizard: the slow-worm.

Neither particularly slow nor a worm, this small, sinuous lizard has a super-smooth body with a coppery or golden shimmer. It looks superficially similar to a snake (of which Britain has three native species), but there are a few ways to tell them apart.

Firstly, although it may require much closer inspection, the slow-worm has visible ears and eyelids, both of which all snakes lack (snakes simply have a clear protective scale ‘spectacle’ over their eyes instead). This means that, unlike snakes, slow-worms and almost all other lizards can close their eyes and blink.

Secondly, the slow-worm prefers invertebrate prey, such as slugs and worms, which it can chew. By contrast, snakes feed on a variety of small mammals, amphibians and birds, and they simply open their mouths and swallow their food whole.

And finally, the slow-worm can do something that no snake can do. If it is grabbed by the tail, it will reveal why its scientific name is Anguis fragilis (‘brittle eel’) – it can autotomise, or cast off its tail. This is caused by sudden muscle contractions creating a fracture at a weak point between vertebrae. As the severed tail involuntarily twitches and squirms around, it catches the attention of whatever predator grabbed it, allowing the rest of the slowworm to escape. It’s a trick that many lizards, legless or otherwise, have perfected. From the stump, a new, cartilaginous tail will grow, and although it’s never as elegant or whip-like as the original, aesthetics are somewhat unimportant in matters of life or death.

Slow-worms are fairly widespread throughout the UK, favouring humid conditions and shaded areas, such as rough grassland, woodland edges, heathland and gardens. Though primarily a burrowing species, they can be seen basking on warm days from March until October, after which they hibernate to escape the coldest months. The corners of churchyards are a good place to see this lizard – they like basking on graves and warm heaps of grass cuttings, their coppery skin glinting in the sunshine. But many times you don’t even need to leave your garden to see a slow-worm – they can be found while digging a flowerbed or compost heap, or underneath bits of old sheets of corrugated iron.

This time of year, in August and September, is when slow-worms are usually born. I say born because unlike many reptiles, which lay eggs, the female slow-worm retains the eggs inside her body until they hatch, so she gives birth to live young. If these youngsters can somehow avoid being eaten by badgers, adders, hedgehogs, cats and even chickens, they may live to be more than 30 years old – and up to 50 years in captivity.

In the next British Wildlife of the Week, we’ll be looking at one of the country’s few carnivorous plants – the sundew.