No cares for water bears: possibly the planet’s toughest animals

There’s a bear in there, and it’s not what you’ve seen on Playschool. With 8 legs, a face like a cannon and a body the size of an exclamation mark, the most bizarre thing about the Water Bear isn’t it’s appearance, it’s the fact that this may well be the toughest animal on the planet.

Waterbear / Tardigrade

These tiny, sausagey (sure it’s a word) creatures, while affectionately known as water bears are actually called tardigrades and they’re hardier than a handful o’ hard-boiled lollies. They can withstand freezing, radiation, toxic chemicals, extreme pH, desiccation, and even the conditions in space – because like any good sci-fi character, they can enter a state of suspended animation.

This transformation into suspended animation is known as cryptobiosis, and it causes the water bear’s metabolism to slow to almost a standstill. So all it’s cells can take a breather. The water bear contracts into a little ball, called a tun, and it’s skin begins to become impermeable (stops letting as much stuff come in and out) and this gives the water bear time to make tissue protecting chemicals that then make it basically indestructible.

A tardigrade tun, Photo: Dr. Ralph O. Schill
A tardigrade tun, Photo: Dr. Ralph O. Schill

What does this cool but complex process allow water bears to do? Well for one thing, to have no need for a fur coat because they can survive instant freezing to -196°C all by their coatless selves. This is pretty remarkable considering temperatures that low don’t even exist in nature. 

The same goes for when you heat things up, tardigrades can sweat off temperatures well over 100°C too. This isn’t surprising considering they can survive total desiccation, where they lose all water from their bodies. In this instance it’s a matter of just add water and the water bear can be revived back to its sausage self.

Water bears also make for great astronauts too, scientists have put them in a vacuum and applied unfiltered solar radiation, as are conditions in space, and they’ve still been able to be revived. So don’t be fooled by this little chubby chap, it’s possibly the toughest animal on the planet, and even in space.

Photo: Eye of Science/Science Source
Photo: Eye of Science/Science Source

I’ll leave you with this last thought, some scientists predict water bears used to be bigger and have evolved smaller over time. Imagine living back in the day and having your own pet water bear you could pat, take for walks and put under extreme conditions to watch it enter suspended animation and then magically revive again.

What fun it would be.


Jönsson, K. I., & Bertolani, R. (2001). Facts and fiction about long‐term survival in tardigrades. Journal of Zoology, 255(1), 121-123.

Jönsson, K. I., Rabbow, E., Schill, R. O., Harms-Ringdahl, M., & Rettberg, P. (2008). Tardigrades survive exposure to space in low Earth orbit. Current biology, 18(17), R729-R731.

Persson, D., Halberg, K. A., Jørgensen, A., Ricci, C., Møbjerg, N., & Kristensen, R. M. (2011). Extreme stress tolerance in tardigrades: surviving space conditions in low earth orbit. Journal of Zoological Systematics and Evolutionary Research, 49(s1), 90-97.

Schmidt-Rhaesa, A. (2001). Tardigrades—are they really miniaturized dwarfs?. Zoologischer Anzeiger-A Journal of Comparative Zoology, 240(3), 549-555.





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