The Bear that Wouldn’t Die

Do the tiny aquatic creatures called tardigrades hold the secret to eternal life?

A powerful wave of nostalgia washed over me recently when I discovered that a microscopic animal called a tardigrade had been voted 2025’s ‘Invertebrate of the Year’. In the early 2000s, when we were assembling the research that eventually became BBC’s QI, the tardigrade was our mascot: a creature that most people had never heard of but, which once discovered, is impossible to forget.

What makes them so special?

For a start, tardigrades have some claim to being the toughest animals on the planet. Also known as ‘water bears’ and ‘moss piglets’, they sound cute – but don’t be fooled. They live anywhere there’s water – five miles down in the ocean; on the polar ice caps; in radioactive hot springs; on top of the Himalayas; on forest floors; on the bottom of lakes; on wet beaches; in alpine meadows; in the miniature ponds created in the cups of leaves; in the moss on your roof; on the ground where your dog pees each morning.

They are plump, microscopic animals that fall into a phylum of their own somewhere between the arthropods (insects, spiders, and crustaceans) and nematode worms. Like those two phyla, their bodies are covered in a cuticle that they shed in order to grow.