Revealed: Secrets of the Camouflage Masters

suchandra · April 18, 2008

According modern science, evolution not only produced accidentally the human brain but also even more complex things like camouflage.

<nyt_headline version="1.0" type=> Revealed: Secrets of the Camouflage Masters </nyt_headline>

19camou.xlarge1.jpg Roger T. Hanlon

HIDING IN PLAIN SIGHT Cuttlefish loses itself at lab in Woods Hole, Mass.

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<nyt_byline version="1.0" type=> </nyt_byline>By CARL ZIMMER

Published: February 19, 2008

<nyt_text> </nyt_text>WOODS HOLE, Mass. — The cuttlefish in Roger Hanlon’s laboratory were in fine form. Their skin was taking on new colors and patterns faster than the digital signs in Times Square.

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Roger T. Hanlon

Octopus at Grand Cayman, where another octopus performed the Moving Rock Trick.

Dr. Hanlon inspected the squidlike animals as he walked past their shallow tubs, stopping from time to time to ask, “Whoa, did you see that?”

One cuttlefish added a pair of eye spots to its back, a strategy cuttlefish use to fool predators. The spots lingered a few seconds, then vanished.

When Dr. Hanlon stuck his finger into another tub, three squirrel-size cuttlefish turned to chocolate, and one streaked its back and arms with wavy white stripes.

“Look at the pattern on that guy,” he said with a smile as they lunged for his finger.

In other tubs, the cuttlefish put on subtler but no less sophisticated displays. Dr. Hanlon’s students had put sand in some tubs, and there the cuttlefish assumed a smooth beige. On top of gravel, their skins were busy fields of light and dark.

Dr. Hanlon likes to see how far he can push their powers of camouflage. He sometimes put black and white checkerboards in the tubs. The cuttlefish respond by forming astonishingly sharp-edged blocks of white.

“We can give them any hideous background,” he said, “and they will try to camouflage.”

Cuttlefish and their relatives octopus and squid are the world’s camouflage champions. But Dr. Hanlon and his colleagues have just a rough understanding of how these animals, collectively known as cephalopods, disguise themselves so well.

Dr. Hanlon, a senior scientist at the Marine Biological Laboratory here, has spent much of the last three decades studying them in his laboratory and on thousands of ocean dives. He said he believed that he finally had a theory for how they achieve their magic.

In fact, he said it could account for all the camouflage patterns made by animals like katydids and pandas. For all the variety in the world of camouflage, there may be a limited number of ways to fool the eye.

Dr. Hanlon’s scientific career was a foregone conclusion. At age 18, he took his first dive in Panama and spotted an octopus hiding on a coral reef. After serving as an Army lieutenant for two years, he entered graduate school at the University of Miami, where he began to study cephalopod camouflage.

He has spent much of his career underwater, swimming around coastal reefs and rocky coastal waters from the Caribbean to South Africa to Australia.

Typically, Dr. Hanlon and his colleagues follow a single cephalopod, filming for hours as it shifts its skin. On some dives, Dr. Hanlon uses a spectrometer to obtain precise measurements of the light in the water and the reflections from the animal. The tedium is interrupted now and then by acts of spectacular deception. Cephalopods do not just mimic the colors of the sea floor or coral reefs. Sometimes, they make their arms flat and crinkled and wave them like seaweed.

Dr. Hanlon has watched octopuses perform what he calls the Moving Rock Trick. They assume the shape of a rock and move in plain sight across the sea floor. But they move no faster than the ripples of light around them, so they never seem to move.

Dr. Hanlon’s jaw-dropping footage has appeared on a number of documentaries. One pirated segment has wound up on YouTube, where it has been viewed hundreds of thousands of times.

Dr. Hanlon approaches normal-looking coral at Grand Cayman Island. When he is a few inches away, half the coral suddenly becomes smooth and white. An eye pops open, and an octopus that has been clinging to the coral shoots away.

Despite thousands of dives, Dr. Hanlon still considers himself a novice in spotting cephalopods. Once, after following an octopus for an hour and a half, he looked away a moment to switch cameras. When he looked back, the animal was gone.

He and his colleagues swam for 20 minutes before realizing it was right in front of them, exactly where they had seen it before. “I was really angry,” Dr. Hanlon said. “They still fool me, even though I think I know what I’m looking at.”

In recent years, Dr. Hanlon has been spending much of his time diving along southern Australia, where a colleague discovered the only major spawning grounds for cuttlefish ever found. Every year, hundreds of thousands of Australian giant cuttlefish gather there to mate and lay eggs. “I’d been searching for a place like that for 25 years,” he said. “The first time I stuck my head in the water, I said, ‘I’ve died and gone to cuttlefish heaven.’ ”

full article:http://www.nytimes.com/2008/02/19/science/19camo.html?_r=1&st=cse&sq=carl+zimmer+revealed&scp=1&oref=slogin