For giant tortoises living in the tropics, you either find a way to get out of the sun, or you die.

Usually, that means waiting out the hottest part of the day behind a rock or beneath the shade of a tree or bush. 

But on the Aldabra Atoll in the Indian Ocean, Aldabra giant tortoises (Aldabrachelys gigantea) have another strategy never before documented in tortoises, giant or otherwise—hiding out in caves. 

What’s more, there’s reason to believe that this behavior is quite ancient, says Dennis Hansen, leader of the team that discovered the cave-dwelling reptiles. 

That's because, over the centuries, the tortoises have worn smooth previously craggy paths as they clamber down to the caves each day.

“The tortoises have used it for a long, long time,” says Hansen, a tropical ecologist at the University of Zurich in Switzerland.

During the