Kings of Camouflage

PBS Airdate: April 3, 2007

NARRATOR: Imagine an alien that can float through space, with a giant brain shaped like a doughnut, eight arms growing out of its head, and three hearts pumping blue blood. This alien lives right here on Earth. It's called the cuttlefish, a flesh-eating predator who's a master of illusion, changing its shape and color at will. It can hypnotize its prey or even become invisible.

MARK NORMAN (Museum Victoria): They've developed this skin that can do the amazing changes in color and changes in shape. And you couldn't get a weirder looking animal.

ROGER HANLON (Marine Biological Laboratory): Every place they go, they are morphing into something that looks a lot like that environment.

NARRATOR: How does an animal that's related to a slug manage such clever tricks?

MARK NORMAN: You get a sense there is a hell of a lot going on in those brains, but we're struggling to, kind of, understand how they work.

NARRATOR: NOVA dives into a stunning and bizarre world, as researchers probe the surprising brainpower and explore the conjuring magic of one of the strangest creatures alive today.

JESSE PURDY (Southwestern University): We are testing an animal that's very alien. It's as close, perhaps, as we're going to get to studying an animal on another planet.

NARRATOR: Kings of Camouflage right now, on NOVA.

NARRATOR: Dive into the oceans off Europe or Australia and you might encounter a strange and elusive animal. This is nature's greatest master of disguise, the cuttlefish. Its visual wizardry and clever behavior have fascinated and mystified scientists for years.

MARK NORMAN: When you come across your first cuttlefishâ¦They are the most amazing creatures. They're either a pair of eyes staring out of a bush of seaweed, or they're these sort of small, alien spaceship. And you couldn't get a weirder looking animal under water.

NARRATOR: Captivated by these bizarre creatures is marine biologist Mark Norman, based at The Museum Victoria in southern Australia.

MARK NORMAN: The thing that fascinates me about cuttlefish is that they are so different from what's familiar to us. And when you dive with them and see all the things that they're capable of, you just can't help being drawn to them.

NARRATOR: Cuttlefish have been performing their own brand of magic for millions of years in oceans around the world, though not in the Americas.

Technically, cuttlefish aren't fish at all, but mollusks—soft-bodied animals without a spine a group that includes snails and clams.

But these animals have no outer shell. They're a kind of cephalopod, along with their more famous cousins, octopus and squid.

Cuttlefish might be lesser known, but they're no less talented. In the blink of an eye, their skin can change color, pattern, even shape.

MARK NORMAN: They've developed this skin that can do the amazing changes in color and changes in shape. And what fascinates me the most is how different cuttlefish species have taken that basic tool that probably evolved for camouflage, and they've taken it a step further and said, "All right, how can we use this in other ways?"

NARRATOR: So what else are these peculiar animals capable of?

There are over 100 different species of cuttlefish. One of the strangest lives in the waters of Indonesia, and Mark Norman has come here to try and track it down.

With the help of local guide Ronald Sarante, Mark will search the reefs for the elusive broadclub cuttlefish, a shape shifter with some particularly weird habits.

RONALD SARANTE (Reef Guide): Okay, are you ready, Mark?

MARK NORMAN: Yep. After you.

The first problem when you come to these sorts of tropical areas is just even finding an animal. You swim over huge areas of reef, and you're probably swimming over lots of animals, but you have no idea they're there, because they're excellent at camouflage.

NARRATOR: Cuttlefish often have favorite stomping grounds. And it's Ronald's local expertise which brings Mark face to face with his first broadclub cuttlefish.

MARK NORMAN: When you first approach cuttlefish, within, sort of, 10 or 15 minutes, you can get fairly close to them. They're checking out you as much as you're checking them out. And that's the most exciting time to sit and watch their behaviors, 'cause after a while they get used to you, and they will allow you to accompany them while they go off to catch food.

And these guys have developed the most amazing way to do it.

NARRATOR: Cuttlefish are often hungry and on the lookout for a tasty treat. Sneaking up in coral camouflage is one hunting trick. But if this fails, the broadclub cuttlefish gives up all attempts at being inconspicuous and instead pulls out all the stops with a dazzling show that seems to stun its prey and leaves it helpless.

How can an animal turn itself into something as flashy as a Las Vegas marquee? Halfway around the world, at the Marine Biological Laboratory in Woods Hole, Massachusetts, Roger Hanlon is trying to deconstruct the cuttlefish's visual pyrotechnics.

Checkers, anyone? Roger's cuttlefish work hard to blend in, even to the most unnatural environments, thanks to their versatile skin.

ROGER HANLON: There's no skin on Earth like a cuttlefish. These animals can change instantaneously. The diversity is fantastic. Chameleons are boring by comparison.

NARRATOR: So how does cuttlefish skin work its magic?

ROGER HANLON: Their skin is extraordinary because it has two ways to produce color and pattern.

NARRATOR: The secret lies in specialized layers of skin cells.

ROGER HANLON: The top layers are the pigmented cells that give you most of the patterning. And they are layered. They have a yellow, a red and a brown.

NARRATOR: One little pigment cell is this little ball of color, all tightly bound up so you don't see it. And it has muscles attached to it. And the muscles can pull that pigment sac out into a little disk of color.

And then when the muscles let go, it just—boink—goes right back in, and you don't see anything. And so it's a very simple mechanism.

Next, there's a deeper layer of iridescent reflecting cells that produce blue and green, along with red and pink. Add a white base and the cuttlefish palette is complete.

ROGER HANLON: There is no limit to the colors they can show in their skin. It's really marvelous.

NARRATOR: Along with color and pattern, the skin can change its texture, too, pushing up bumps along its surface.

ROGER HANLON: Well, this enables you to fool any visual predator there is. It's much better than the Harry Potter invisible cloak. There is no comparison. This is real camouflage. They're doing it the real way.

NARRATOR: To match their surroundings, cuttlefish rely on their eyesight. As strange as it may appear to us, their w-shaped pupils provide excellent vision.

ROGER HANLON: So here you have this magnificent eye. And this eye can see things very, very well.

NARRATOR: Visual cues go straight to the brain, and the brain, in turn, sends instructions right to the skin cells.

ROGER HANLON: It's the fastest possible way—direct control by nerve. And so we call this electric skin, because as soon as the information gets to the brain, the information is taken out of the brain, goes to the skin, and says, "Do this." And it's just boom, boom, boom, boom. You know? It's really quick.

NARRATOR: The cuttlefish's electric skin usually works for self defense, to make it disappear into the background. But clearly, the broadclub found a new use for its changeability.

ROGER HANLON: My guess is that their skin evolved for camouflage because as soon as they got rid of the big shell, they had to hide from predators. I think, after that, the skin then evolved these patterns for communication, for mating and courtship, and in some cases, even for tricking shrimps and fishes that they're going to eat.

NARRATOR: Back in Indonesia, Mark Norman wants to know exactly what triggers the broadclub to turn itself into the ultimate exhibitionist.

MARK NORMAN: I'm very interested in this strange feeding behavior. And so, to try and understand what's going on, we need to get them to do this behavior on cue, whenever we want it to happen. By handing them live prey or decoysâ¦they start doing the behaviorâ¦you can start analyzing what is it that sets them off, when it works best.

NARRATOR: Mark's first offering of small crabs—their favorite food—is welcome. But it doesn't trigger too many light switches.

Next step: offer a bigger lure, like a toy lobster. Will this do the trick? The lobster proves irresistible for as long as it looks alive. Once it stops moving, the broadclub seems to lose its motivation.

When Mark brings the lure back to life, the performance promptly resumes, but not for very long. This cuttlefish is getting bored with toys and is ready for the real thing. Cuttlefish like their meals alive.

So, does the size of a potential meal trigger these light shows?

MARK NORMAN: Well, it seems that for smaller prey, or once they're well fed, they almost don't bother doing it. But with the bigger lures and the bigger crabs, the cuttlefish do a really good, detailed display, to sort of stun or to dazzle the prey long enough to slow them down. And then the cuttlefish could come in and nail them in the way it wanted to. In the case of the crabs, the cuttlefish wanted to grab it from behind, so these big dangerous claws are out of the way of the attacker.

NARRATOR: It's all about positioning. If you don't want to lose one of your arms, you've got to get just the right grip on your prey.

With his next offering, Mark gets an even better view of the show.

MARK NORMAN: The most interesting is when you offer a broadclub cuttlefish a live animal in a glass jar. It gives you a perspective where you can move the jar around and see what it looks like from the prey's point of view. It looks like they're, sort of, effectively hypnotizing their prey. It's fantastic.

They get very excited, come in and nail the glass, get confused. The water is solid and they can't get through the water, and they continually try and get in on different angles on this glass container.

NARRATOR: Every cuttlefish starts off with the same hungry determination, but Mark can't fool them for long.

MARK NORMAN: They learn really quickly. It only takes a few strikes before they realize they're not getting the crab, it's a total waste of time. You can sort of see them mentally turn off and sort of drift away.

You get a sense there is a hell of a lot going on in those brains, but we're struggling to, kind of, understand how they work.

NARRATOR: As alien as they seem, cuttlefish do share something with us: big brains. While humans have one of the biggest brain-to-body ratios among mammals, cuttlefish and octopus top the list for all invertebrates.

Their large brains most likely evolved hand in hand with their complicated and changeable skin.

ROGER HANLON: There are up to 20,000,000 of these pigment cells in the skin, and to control 20,000,000 of anything is going to take a lot of processing power. And it has to have a large brain to make all this work.

NARRATOR: But does a big brain necessarily mean cuttlefish are intelligent? Looking for answers is Jesse Purdy, a comparative psychologist at Southwestern University in Texas.

JESSE PURDY: Can we know more about ourselves by studying another animal? And as a comparative psychologist I think we can. By understanding their world a little bitâ¦can give us more insight into our world.

NARRATOR: But how do you measure an animal's brainpower?

JESSE PURDY: The work with cuttlefish is at a very early stage. Not a lot of people have done learning experiments with cuttlefish. So we need to start at a very basic stage and then move up the ladder.

NARRATOR: Here at Southwestern, cuttlefish are being tested for the most basic levels of learning. For example, if you put a wind up plastic fish into a cuttlefish tank, at first it mistakes it for food. But once it realizes how unappetizing the toy is, from then on, the cuttlefish will ignore it.

But can you teach the cuttlefish that the toy has a different meaning?

JESSE PURDY: The experiment that we do with Troy, the toy fish, is actually asking that question. The experiment, as you see it, looks very simple. You see somebody simply drop a toy fish in and then, a little bit later, drop a fish in.

NARRATOR: One question is whether or not the cuttlefish can learn to associate the toy fish with the promise of food.

Sure enough, if Troy the toy is consistently joined by a real fish, then the cuttlefish will pay close attention to him. But with a separate test group, Troy swims alone and no meal appears, so for those cuttlefish Troy will hold absolutely no interest.

JESSE PURDY: So we're seeing a difference between these two groups, and the difference is learning.

NARRATOR: The next step is to see if the animal can learn to do something in order get fed, like pressing a button on a vending machine, or, in their world, hitting a jar to receive a reward.

Sound familiar? Remember when the broadclub cuttlefish was shown crabs in a jar? After a few frustrated jabs, it quickly lost interest. But in this test, some cuttlefish are rewarded from an automated feeder. Strike the jar, get a snack. These cuttlefish quickly learn this trick and will keep hitting the jar.

Cuttlefish easily master the most basic learning skills, so researchers need to come up with more difficult challenges if they want to really measure their brainpower.

JESSE PURDY: Are cuttlefish intelligent? I'm absolutely convinced that they are. So where do we go from here? Is it the level of cognitive complexity that we think these animals are capable of? Have we seen how smart they are, at this point? And I don't believe we have.

NARRATOR: For any creature, when it comes to intelligence, what matters most is how it helps you survive in the real world so you can pass on your genes to a new generation.

And there is one place where the wiliest cuttlefish play their most elaborate tricks. It's late May in southern Australia. Life on shore is just settling down for the winter. But beneath the waves, things are heating up.

It's the mating season for the Australian giant cuttlefish and thousands of them are swimming into the spawning grounds.

MARK NORMAN: Giant cuttlefish coming together to breed is the most dazzling... shows that they can do in these color and shape changes. And it's spectacular when you see them just come to life in these big displays. It's sort of like they rip off their Clark Kent outfit and out comes Superman or "Supercuttlefish."

NARRATOR: Giant cuttlefish can grow over three feet long. Eye to eye, the big males try to outdo each other with the most intimidating body patterns. Smaller females seem unimpressed.

MARK NORMAN: It's usually a very secretive behavior in lots of other animals, including other cuttlefishes, and you're lucky to even come across breeding aggregations. But to see thousands of them here is just spectacular. And so for several months they give up the pretence of looking like seaweed or hiding in amongst the sand or the mud, and they go, "Bugger it. We're just going to look fantastic, and we're going to fight with each other, and we're going to impress females."

And they totally ignore us. We can sit in amongst them, they can almost sit on our head, and that's when the best displays come out.

NARRATOR: During mating, males outnumber the females, sometimes 10 to one. And they're all looking for the chance to pass on their genes. While a female lays eggs beneath a rock, a big male tries to monopolize her, staving off the other hopeful suitors.

Sometimes intimidation alone won't work, and the competitors hurl themselves into a violent and bizarre looking wrestling match.

Like an octopus, they'll squirt out an inky smokescreen when it's time for a hasty retreat.

But size and strength aren't the only ways to impress the ladies.

Thanks to the cuttlefish's skin morphing talents, the smaller males have a clever trick up their sleeve.

MARK NORMAN: The really interesting thing in this system is actually far less obvious, and when you first dive with them, you don't see it. It takes a while before you realize what's going on.

The small males, who have no chance in a contest with a big male, are actually doing something completely different. They're effectively cross-dressing. They're dressing up as a female, by pulling in their webs and putting on this mottled color pattern and gliding past these big, aggressive male, pretending to be a female, and will come in to the female underneath.

And what happens is, as another big male comes in and a potential conflict between these big guys starts up, the sneaker males start mating with her, successfully mate with the female, while the big guy isn't even aware of it.

NARRATOR: The cross-dressers' success is all the more impressive because the females often play hard to get, as Roger Hanlon has seen firsthand.

ROGER HANLON: These females are very picky. They reject 70 percent of approaches for mating. Yet they only reject 30 percent of the cross-dressing males. So this trick gets them in the door, so to speak, past the fighting male, and they're accepted by the female.

NARRATOR: The little guy may have crossed one hurdle, but a female's welcoming embrace alone won't guarantee reproductive success.

ROGER HANLON: Mating in a cuttlefish is a strange affair. They go head to head, we call it. Then they join those eight arms together from each animal. Then the male has one special arm underneath, in which he reaches back and he pulls out a packet of sperm. And then he just places that packet of sperm right up amidst the arms of the female.

NARRATOR: It's the male's job to hand over the sperm. But once he does, fertilization is up to the female. She's already mated with multiple partners and is storing their sperm in pouches under her arms.

ROGER HANLON: So now this female choosing, this takes on a new dimension. She not only chooses mates during the day, but she has some choice and some influence over which sperm get used. And guess what? The male can do nothing about that.

NARRATOR: So whose sperm wins out in the end? There's only one way to find out.

ROGER HANLON: We actually do paternity testing just like humans do in a court of law. And we use the same technique, and it's very precise.

NARRATOR: Roger was part of a team that extracted DNA samples from all the participants—the mother, her partners, and the babies—to find out, "Who's the daddy?"

ROGER HANLON: One of the biggest surprises is that the cross-dressing males got the very next fertilization. And we did not expect this at all. The only reason we could think of is that this is a very bold, smart tactic. And the females may be acknowledging that in, sort of, evolutionary terms. So this trick, as strange as it seems, is very successful.

NARRATOR: Over the course of a couple of weeks, each female will lay hundreds of eggs sired by many fathers, filling up the crevices on the undersides of rocks.

The eggs will remain there for three to five months, until the babies are ready to hatch. But the newborns will be orphans. The mating season marks the end of the giant cuttlefish's lifecycle, and the parents won't survive to see the birth of the next generation.

MARK NORMAN: It looks like cuttlefish only have one mating season. It can last for up to six or eight weeks, but it's only the one session, and then they all die. So some burn bright and die young, some live slightly longer and die, but all of them don't live very long. So it's probably only 18 months to two years old, is how long they live.

NARRATOR: With such a short lifespan, it's even more surprising how smart these creatures seem to be.

Intelligence is all about learning to adapt to new situations. Here at Millersville University in Pennsylvania, Jean Boal wants to figure out just how much, and how fast, cuttlefish can learn.

JEAN BOAL (Millersville University): I think cuttlefish are remarkably intelligent animals. So the issue is, "Am I smart enough to find out how smart they are?"

NARRATOR: For nearly 20 years, Jean has been running tests with cuttlefish and their more famous cousin, the octopus.

JEAN BOAL: I began with octopuses because there are no cuttlefish in the Americas. So, like most Americans, I'd never heard of them.

Octopuses love to destroy lab equipment. If they can possibly rip something apart, they will. And in terms of their performance in experiments, octopuses are unbelievably erratic. One day they will be brilliant, and the next five days they'll act like they don't know anything at all.

Once I got started working with cuttlefishâ¦they're very practical animals to work with. They're very easy, and they're very engaging. And then, on top of that, it looks like their brain size, relative to body size, is perhaps even larger than octopuses.

And it would be really wonderful if we could just figure out what they're doing with all that brain.

NARRATOR: To test her cuttlefish, Jean has created a special enclosure, fashioned from a plastic trash barrel, which the animals must try to escape from.

JEAN BOAL: The real difficulty for me is to find out how to ask them so that they can tell me what they know. They're certainly not going to tell me verbally. So I have to design a clever enough experiment that their behavior can tell me what they know. And that's what's really challenging and really, in many ways, exciting.

NARRATOR: Thirteen research subjects with names like Bubbles, Goofy and Crook, are tested three times a day over several months. Their job is to negotiate a simple maze and to find their way out as quickly as possible.

JEAN BOAL: The cuttlefish maze has a starting tube where they go in and just calm down for a few seconds.

In she goes. She is in.

WOMAN WITH STOPWATCH (Millersville University Student): Three, two, one.

JEAN BOAL: Door is open.

And then there is a larger arena, and they have to decide whether to go right or left. And there are features in there to help them to distinguish that.

NARRATOR: In each trial, only one of the two exit doors is open. The cuttlefish has to look for clues to pick the right one. If there's a piece of plastic seaweed in the enclosure, then the striped door will lead to freedom.

But if the cuttlefish enters the maze and sees a big brick instead, then the solid door is the way to go. If the cuttlefish picks the wrong door, she'll be blocked by clear plastic.

JEAN BOAL: All right. This is Tad.

NARRATOR: So, can a cuttlefish learn these rules?

JEAN BOAL: And in you go.

The current problem that I'm working on is conditional discrimination learning—can you remember the two things at once?

Open. She's in.

WOMAN WITH STOPWATCH: Starting.

JEAN BOAL: And we have good evidence that the cuttlefish can do this, which is truly extraordinary for an invertebrate animal.

There she goes. She is out.

WOMAN WITH STOPWATCH: Great time.

NARRATOR: The cuttlefish are able to recognize and remember at least two rules or conditions for finding the open exit. That's a level of intelligence much more common among creatures that possess a backbone.

JEAN BOAL: So what's really exciting about cuttlefish intelligence is we know that their relatives are clams and snails. Those are not animals that had a need for great intelligence. So whatever happened to cuttlefish was different.

ROGER HANLON: I think one of the reasons they have to be so smart is they've given up their external body armor like a snail has. They're soft. They're vulnerable. They can be eaten. Everything in the ocean eats a cuttlefish. So these animals have to get by by their wits, so to speak. They have to be smart. I think it's safe to say that cuttlefish are definitely as smart as fish. And, in fact, they're as smart as maybe even some animals like birds and mammals and other things we consider to be smarter animals.

NARRATOR: The cuttlefish's big brain, together with its amazing camouflage, probably evolved so they could survive in dangerous environments filled with hungry fishes. But one cuttlefish might have acquired another secret weapon.

Back in the tropics, Mark Norman and Ronald Sarante are searching for Mark's favorite cuttlefish, who's managed to thrive in a unique and threatening landscape.

MARK NORMAN: These muck dives, on sand and mud areas, are very different. They feel very solemn and dark and moody. You have these black plains going everywhere. The few animals you do pass are either covered in poisonous spines or pretending to be dead leaves. You get this feeling that it's just oppressed by predators.

NARRATOR: This is a place of the weird and the wonderful, where standing out or blending in all depends on whether you are predator or prey. It's one of the few places you'll find the rare mimic octopus.

But the strangest of them all is a creature called the flamboyant cuttlefish. For a start, it's walking, not swimming.

MARK NORMAN: It's still really foreign for me to watch a cuttlefish walking around on the seafloor. They actually look like these prehistoric lumbering monsters, sort of walking through these ancient black deserts.

NARRATOR: This enigmatic animal has made a huge impression on Mark, despite the fact it's only a couple of inches long.

Although the flamboyant cuttlefish walks most of the time, it can swim, but just barely. What's wrong?

Cuttlefish get their name from their cuttlebone, a chalky internal shell filled with gas that allows them to float. But the tiny flamboyant's cuttlebone has shrunk so much it can't float for very long.

MARK NORMAN: They seem to have a really gentle nature. They flap up into the water, they settle down again, and they go back to walking along the seafloor, back into camouflage, back into feeding almost straight away, looking for something to eat, out on the mud.

NARRATOR: Like its big brothers, this cuttlefish has to grow fast and is often on the hunt. But to catch a tiny glass shrimp takes very good eyesight and patience.

Stalking its meal in spiky disguise, it aims its feeding tentacles like a pool player, ready to hit the target.

Eat and be eaten. For every creature there's a hunter lurking. These open plains don't offer much cover, and to be out and about in broad daylight is risky, especially if you're neither fast nor big.

Predators are a constant threat, and this is when the flamboyant cuttlefish earns its name. Whenever it feels threatened, it puts on an alarming display.

MARK NORMAN: When something comes too close, they flare up the arms, and they walk around flashing these colors and advertising these really bright color patterns. And I think this is advertising the fact that they're poisonous to eat. If anybody gets too close, even, like, a diver, they show all the bright colors. And it says, "Back off, I'm poisonous." It's either pretending it's deadly as hell and trying to mimic something else that is dangerous, or it's walking around confident that it itself is deadly.

NARRATOR: Clearly, the flamboyant stands out from the rest of the cuttle pack. But is it just a big bluff or the real thing? Is it poisonous or not?

To find out, Mark and Ronald need to look for a full-grown animal, and freshly laid eggs are a good sign that a mature female has passed through recently.

Hidden under coconut shells, they find some flamboyant eggs. The mother should be nearby.

In this bleak landscape, it's a challenge for a flamboyant mother to find a safe spot for her eggs. Without rocks or caves, old shells are the next best thing.

Compared to the egg-laying frenzy of her giant cousins, hers is a quiet affair. She lays up to a hundred eggs, a truly exhausting task. And with the laying done, she'll soon die naturally.

But there's one more important mission she can help with: assisting Mark with his toxin studies.

MARK NORMAN: If this animal does turn out to be deadly, to be toxic, it will be the first cuttlefish in the world that's known to be poisonous. We could be seeing a whole change in the evolution of these animals.

I'm really fascinated in what it is about them that's poisonous. Do they have a poisonous bite? Is all their flesh poisonous? Can they squirt poisonous ink?

NARRATOR: Mark has to take her back to venom labs in Australia to unravel her potentially deadly secret.

The winter storms have finally passed, and the deserted mating grounds of the Australian giant cuttlefish slowly begin to warm. The parents died more than three months ago, but the next generation of giants is just getting started.

Sheltered in their rocky nurseries, the eggs enclose pin-sized embryos. Sucking up energy from the yolk, they've grown eight arms, red-dot eyes and their family trait, the cuttlebone. In the final month the embryos' eyes fully develop, and, still hanging upside down, they start moving around.

By now the eggs' soft shell has stretched to double its size and the bodies have outgrown the yolk ball. Once they start floating upright, the little giants prepare for the outside world. All their organs are now developed, and they can already change the color and shape of their skin.

After about four months, they squirt a special acid from the tip of their tail to burn a hatching hole through the rubbery shell.

Barely the size of a fingernail, the tiny giants emerge like miniature adults, with suckers, ink and all. Nobody knows how many will survive.

In a few days they'll start hunting tiny shrimp and perfect their shape-shifting repertoire.

But they've got to watch out: they're on the menu for almost anything with a fin. Sharks, big fish, seals, they all love cuttlefish. Their meaty bodies without spines or armor make cuttlefish a protein-rich meal.

Camouflage is the cuttlefish's main defense. While they're invisible, they're safe. But once the cover is blown, their only chance is to disappear behind an inky cloud.

Dolphins have developed a special taste for cuttlefish. But rather than gorging on the whole body, they prefer to just pick off their soft arms and heads. Leaving behind tattered bodies, they provide a free meal for many more creatures.

But cuttlefish don't just end up on ocean dwellers' menus. In many countries, humans are one of the cuttlefish's most voracious predators. Cuttlefish, octopus and squid are eaten around the globe, harvested on a large scale. The total reported world catch is more than 3,000,000 tons per year, worth more than six billion dollars. Our taste for all things calamari overwhelms even their best camouflage.

But is there one cuttlefish no one should ever eat?

Back at Australia's Institute for Molecular Bioscience in Queensland, Mark Norman is about to find out if the colorful flamboyant cuttlefish is truly poisonous or just a poser.

MARK NORMAN: That's worth looking at.

Toxicity is really rare in these sorts of animals. There's thousands species of octopus, squid and cuttlefish, and in all the world, there is onlyâ¦blue-ringed octopuses and, just recently, the little striped pajama squid are the only ones that are known to be, to be poisonous, to be very deadly. And so, trying to understand the behavior of this strange little cuttlefish, I think it's really important that we find out whether it's pretending to be something else that's dangerous or it itself is dangerous.

NARRATOR: Toxins could be anywhere, from the skin to the inner organs. If the flamboyant's bite is toxic, its saliva will contain the poison, just as in the blue-ringed octopus. But it could also be mixed with its ink. Mark needs to analyze all body parts.

And the results?

MARK NORMAN: Well, it turns out the flamboyant cuttlefish is toxic. It's as toxic as blue-ringed octopuses. And blue-ringed octopuses have killed humans from their bites, so we've got the first deadly cuttlefish in the world. And it's amazing on a couple of levels. First of all, it's actually poisonous flesh, the muscles themselves are poisonous. So this is the first time that flesh that is deadly has been reported in any of these groups of animals. And secondly, the toxin itself is not known. It's some completely different class of toxins. And toxins like those could be the key to whole new discoveries for lots of human medical conditions.

NARRATOR: But beyond any potential medical use, the toxin is exciting to Mark because it helps explain the flamboyant cuttlefish's oversized confidence.

MARK NORMAN: This is a fantastic result, because it makes sense of what we're seeing in the wild. And this toxicity, this poisonousness is probably what's underpinning the whole weird behavior of the animal. And the fact that a group of animals that normally swim around or spend a lot of time trying to be camouflaged, have become so obvious, have given up swimming, are walking everywhere, it's like a major step towards a whole new line in the evolution of these animals.

NARRATOR: Evolution means change, so maybe in a few million years, the flamboyant will march on eight legs right onto the beaches. Or the broadclub will hypnotize its predators as well as its prey. Perhaps the Australian giants will invent even more daring strategies to outwit their rivals.

Cuttlefish are amazing and perplexing creatures, and we're still trying to understand how all this talent evolved.

JESSE PURDY: We are testing an animal that's very alien. I mean it's as close, perhaps, as we're going to get to studying an animal on another planet. And is that exciting? That's very exciting.

ROGER HANLON: We do not know how smart or clever a cuttlefish is, because every time we go and do a serious bit of field work or a lab experiment, we continue to learn new things about their capabilities for learning or memory or hiding. So I think we have much more to learn.

MARK NORMAN: I hope in my 80s and 90s I'm still wandering around under water with a walking frame, following these things around, because it will take a hundred lifetimes to get a handle on these animals.

NARRATOR: Cuttlefish continue to dazzle with their outward displays, but exactly what goes on inside their heads will remain, for now, the real mystery.