The Peruvian Amazon rainforest is bursting with life, but it's a hard place to make a living, especially when you're small.

Competition... is fierce.

Violence and betrayal are everywhere.

Up here, in the canopy?

These trees have made it.

Lots of leaves.

Plenty of sunlight.

But down here, on the forest floor, it's another story.

This sapling desperately needs to grow, to get more sun.

And in the meantime, it's vulnerable.

It doesn't have many leaves yet.

Each one is valuable.

Losing just a few could be its demise.

So this young tree, it's called an Inga, enlists bodyguards.. hundreds of them.

These big-headed ants swarm over the sapling, fighting off any leaf-eating intruders, like this caterpillar.

The price of protection: a meal: sugary nectar.

The tree serves it up in ant-sized dishes called nectaries.

Both the ant and the tree have something to gain from the deal.

This is called "mutualism."

But that only works when both sides play by the rules.

Here's another intruder.

See how the ants rush to meet it?

But they aren't biting or stinging it.

They don't attack it like they're supposed to.

Instead the ants just... watch... as the caterpillar gorges on the fresh leaves.

They're just letting it happen.

Why?

Because they found a better deal.

See how the ants tap on the caterpillar's rear with their antennae?

Those two little pits on the caterpillar's back are called tentacle nectaries.

When the ants tap, the nectaries secrete drops of nectar.

It's made of sugar that the caterpillar drained out of the leaf.

In exchange for the payoff, the ants give the caterpillars free access to their so-called partner, the Inga tree.

They've been bribed.

As for the tree?

It's left weaker, a little less likely to make it up to the canopy.

And that's the sad story of the young Inga.

Sold out for a drop of sugar water by a fairweather friend.