[Aaron] If he's disturbed by sound, he vibrates.

[Matt] One of the perks of being a scientist

is that unlike the rest of us,

you don't get in trouble for yelling at caterpillars.

[Aaron] That's amazing!

[Matt] Field biologist Aaron Pomerantz

came across this one in Peru and shouted at it.

[Aaron] Lower frequencies.

[Matt] To which the caterpillar responded by unfurling

strange tentacle-like structures called tubercles.

And that's not normal.

Well, I guess it is for the still

poorly-understood tentacled caterpillar.

What's fairly clear, though, is that this

weird behavior is an anti-predator tactic.

The caterpillar probably deploys the structures

by pumping them full of hemolin,

the arthropod equivalent of blood.

If something like a bird swoops in on the caterpillar,

the sound of those wing beats may just

be enough to trip the tubercles.

So how does a caterpillar hear the predators coming?

Well, each of those tentacles is tipped

with tiny hairs that may be picking up

the vibrations associated with sounds.

So they're like ears, very tentacle-y ears.

And notice that those tips are bright white,

which might serve to startle would-be predators.

If that doesn't work and the fiend takes a bite

of the tentacle, the structure may snap off,

just like a lizard would lose its tail.

This is certainly one of the world's

most bizarre caterpillars, but others

have different defenses such as venomous spines.

Caterpillars go through all of this trouble because there

are few things as helpless as a sluggish tube of flesh.

There's really no shortage of predators

that have them on the menu.

But why not just grow straight into a moth or butterfly?

One reason why this may be evolutionarily beneficial

is that the caterpillars and adults

don't compete for the same resources,

freeing up more food in the ecosystem.

The downside?

Well, every so often a scientist comes around

and yells at you. Crazy tentacles!

Oh my god, oh!