In Utah, USA, there grows a being that gathers up everything we think we know about trees and throws it into the water: Pando, a colony of 47,000 genetically identical aspen stems, connected by a single shared root system across 40 hectares. It weighs around 6,000 tons - the largest living being on the planet by mass - and it is, by estimates, 12,000 years old. And now, for the first time, scientists have heard it from within.

Sound artist Jeff Rice placed a hydrophone - an underwater microphone - into the hollow of a branch and ran it down to the root system. During a storm, the device recorded a deep, muffled rumble. „I believe what's being heard is the sound of millions of leaves in the forest, whose vibrations travel through the tree, descend down the branches and settle into the soil," Rice explains.

Even more intriguing is the second finding: the hydrophone registered a knock on a branch nearly 28 meters away - a distance the sound wouldn't reach through the air. This supports the theory that the whole colony really is connected underground, although the researchers carefully hedge: further experiments are needed to rule out the possibility that the sound traveled through the soil itself.

The organization Friends of Pando, which invited Rice as artist-in-residence, sees in the recordings far more than art. „Wind turned into vibration traveling through the root system can non-invasively reveal to us how Pando's vast, hidden hydraulic system works," says founder Lance Oditt. The next steps: tracking the movement of water, the connectivity of the branches, insect colonies and the depth of the roots - all through listening.

And to close, the obligatory bitterness: a being that survived 12,000 years - entire civilizations, ice ages, empires - is today endangered by land clearing and by the disturbed balance between predators and herbivores. The giant that outlived us all may not outlive precisely us. If a 6,000-ton tree can speak, the question is whether anyone up here is listening.