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The full story: Leafcutter Ants
The complete narration of this episode. Tap a time to jump to that moment in the video.
0:00 Snip
Snip. High in a tropical forest, a tiny pair of jaws slices into a leaf. What happens to this one green piece next is one of the strangest stories in nature.
0:14 Leafcutter ants
This is the journey of one leaf, and of the ants that carry it. The leafcutter ants of the Americas.
0:22 The cutter
The cutter is a worker ant, and like every worker in her colony, she is female. As she cuts, she vibrates her jaws, and the leaf gives way, one bite at a time.
0:36 The march home
Then she lifts it. A load many times her own body weight, held high above her head. And she starts the long walk home. She is not alone. Thousands of her sisters march on the same highway, a trail they clear and keep clean themselves, stretching through the forest for well over a hundred meters.
0:57 The scent trail
How do thousands of ants all find the same path? The scouts mark it with scent. A chemical trail, laid from a gland in the tip of the body, that tells every sister: food, this way.
1:11 The bodyguard
But look closer. On top of the leaf, there is a passenger. A tiny worker called a minim. She is not resting. She is a bodyguard. Parasitic phorid flies hunt the carriers, trying to lay their eggs on them. The little rider helps keep them away.
1:29 Not all the same
And not every ant here looks the same. Workers come in very different sizes. The smallest care for the garden and the young. The mid-sized ones cut and carry. And the giants, the soldiers, with huge heads and powerful jaws, stand guard against attackers.
1:48 An underground city
The trail ends at a hole in the ground. Beneath it lies a city. Thousands of chambers, reaching more than six meters deep, home to as many as eight million ants.
2:01 The city breathes
And this city breathes. Millions of ants and their gardens give off carbon dioxide. So the nest is built with openings in the center and around the edges, and the wind blowing over the mound pulls stale air out, and fresh air in.
2:18 The twist
And here is the twist. After all that work, the ants never eat the leaf. Not a single bite. The leaf is food for something else.
2:29 The fungus garden
Deep in the nest, smaller workers chew it into a soft paste and press it into a living garden of fungus. A fungus that lives only with these ants. The ants feed the fungus, and the fungus feeds the ants, growing tiny swollen tips packed with food for the colony and its young.
2:50 The next generation
The garden also feeds the next generation. The queen’s eggs hatch into soft, helpless larvae. Nurse ants carry them, clean them, and feed them on the fungus, until they grow into new workers.
3:05 Who farmed first?
Ants like these have been farming fungus for tens of millions of years. Humans started farming only about twelve thousand years ago. The ants got there first.
3:17 The war on mold
But every farm has pests. A parasitic mold called Escovopsis can attack the garden. So the ants fight back. They weed out infected pieces, and many carry bacteria on their bodies that make chemicals to help hold the invader off. Medicine, grown on their own skin.
3:37 The waste crew
When the garden is used up, the old material goes to a special crew: the waste workers. They carry it away to dump chambers, or to heaps outside. And they keep apart from the rest of the colony, so that disease does not spread.
3:54 One queen
At the heart of this city lives one queen. She can live for more than ten years, laying millions of eggs. Every ant on that trail, every cutter, every gardener, every bodyguard, is her daughter.
4:08 The nuptial flight
Once a year, winged young queens and males take to the sky. Each queen mates in flight, then lands, breaks off her wings, and digs a new nest, alone. Hidden in a pocket inside her mouth, she carries a small piece of her mother's fungus garden. The seed of a brand new farm. Most of these queens will fail. Only a very few will ever raise a colony.
4:34 A leaf is never just a leaf
Back on the forest floor, the light fades, but the highway keeps moving. Another leaf is cut. Another journey begins. Because for the leafcutter ant, a leaf is never just a leaf. It is a farm, a feast, and a future.