British Wildlife of the Week

Yellow-tailed scorpion

Wait, what? Scorpions in the UK? Surely not! Aren’t scorpions only found in hot, dry environments? Well, it’s certainly true that scorpion diversity is greatest in subtropical regions, but these tough little arachnids actually live on all major landmasses apart from Greenland and Antarctica, and in virtually every terrestrial habitat. However, the further north you go, the more scorpions struggle to cope with increasingly colder temperatures. The northernmost natural occurrence seems to be at Medicine Hat in southern Canada, where the aptly-named northern scorpion lives. But a colony of the European yellow-tailed scorpion has established itself one degree further north, in Sheerness on the Isle of Sheppey in Kent, here in the United Kingdom.

This scorpion can naturally be found in crevices on rocky outcrops in southern Europe, but in the Britain Isles it lives a somewhat more precarious life. Though occasionally sighted in and around a number of coastal towns in southern England, its largest and most well-known population lives on the south-facing, sunbaked, crumbling walls at Sheerness Docks. Given its limited range in this country, you might think that the scorpion is a recent addition to our fauna, but it has probably been here for more than 200 years. This clandestine stowaway is thought to have arrived on merchant ships in the 19th century and apparently found Kent to its liking.

The fact that a subtropical animal has managed to survive here at all, especially during winter, is quite miraculous. But survive they have, and the 10,000–15,000 scorpions that now live at Sheerness Docks have made it into the record books as the northernmost colony of scorpions anywhere in the world.

Like other scorpions, the yellow-tailed scorpion glows fluorescent turquoise under ultraviolet light, blazing like a beacon. Why they do this is not fully understood. It’s certainly very useful for scientists who wish to locate scorpions at night – they merely use UV lights to illuminate them in the dark – but how do the scorpions benefit? Perhaps they can detect this fluorescence even under normal conditions, allowing them to locate rivals and mates more easily.

But recently, a new theory has been proposed. In the hour before moonrise, the air is filled with ultraviolet rays that are invisible to most animals. Chemicals in the scorpion’s skin react to the UV rays and act as an early warning system, telling the scorpion that the moon is on its way. If the scorpion detects that a full moon is imminent, it will often retreat back to the safety of its burrow to avoid its own predators, such as desert foxes.

In the next British Wildlife of the Week, we’ll be looking at the bearded tit – a bird whose name is doubly incorrect for it is neither bearded nor a tit.