How rogue waves are created in the ocean : understanding rogue ocean waves may be simple after all

From Georgia University

An international team of scientists has developed a relatively simple mathematical explanation for the rogue ocean waves that can develop seemingly out of nowhere to sink ships and overwhelm oil platforms with walls of water as much as 25 meters high.

The waves stem from a combination of constructive interference – a known wave phenomenon – and nonlinear effects specific to the complex dynamics of ocean waves.
An improved understanding of how rogue waves originate could lead to improved techniques for identifying ocean areas likely to spawn them, allowing shipping companies to avoid dangerous seas. Furthermore, new insights into the unsolved problem of wave breaking and into the wave manifestation of light are to be gained, according to the researchers.

Based on an analysis of the two famous real world Andrea and Draupner rogue waves observed at different oil platforms in the North Sea over the course of a decade, and the recently observed Killard rogue wave at a site for marine renewable energy off the coast of Ireland, the research was reported this week in the journal Scientific Reports.
The work was done by researchers at the Georgia Institute of Technology, University College Dublin, and the Institut FEMTO-ST CNRS-Université de Franche-Comté.
“We saw similar wave behaviors at all three rogue wave sites,” said Francesco Fedele, a professor in the Georgia Tech School of Civil and Environmental Engineering.
“We found that the main mechanism responsible for generating these waves is the constructive interference of elementary waves due to directional dispersive focusing enhanced by second-order bound nonlinearities.”

Rogue waves have been observed in oceans around the world.
They typically last only 20 seconds or so before disappearing, and are different from tsunami waves that can travel great distances after being created by underwater earthquakes or landslides.
Earlier research had suggested a phenomenon known as “modulational instability” to explain the rogue waves.
That theory had been demonstrated in laboratories, but didn’t adequately explain the complex three-dimensional waves that were being measured in the open ocean without boundaries to constrain them. As a result, energy is not ‘trapped’ as in a long unidirectional channel.
Instead, it is free to flow and spread directionally diminishing any exchange mechanisms between neighboring waves, Fedele said.



Though ocean waves have a predominant direction, in the open ocean, waveforms from other directions can arrive.
In rare conditions, those waves arrive in an organized way or almost in phase, leading to an unusual case of constructive interference that can double the height of the resulting wave.

But this doubled height still cannot explain the size of the rogue waves observed in the North Sea – and elsewhere.
That difference can be accounted for by the nonlinear nature of the waves, which are not sinusoidal – but instead have rounded troughs, along with sharp peaks that result from the water being pushed upward against the pull of gravity.
“You have to account for the nonlinearity of the ocean, which is manifested in the lack of symmetry between the crests and the troughs,” said Fedele, who also has an appointment in Georgia Tech’s School of Electrical and Computer Engineering
 “These nonlinear effects can produce an enhancement of 15 to 20 percent in wave height, which adds onto the effects of constructive interference.”

Using advanced mathematical techniques, the researchers modeled how waves could combine in very unusual circumstances to produce the Draupner and Andrea rogue waves measured at two different oil platforms in the North Sea in 1995 and 2007 and the Killard rogue wave observed in 2014 off the coast of Ireland.
Their model’s predictions match the waves measured.
“We describe the complex energy flow of a wave field by what we call its directional spectra,” said Frédéric Dias, a professor at University College Dublin.
“What we have shown is that by combining knowledge of this spectra and using mathematics that accounts for second-order nonlinearities, we can reproduce the measured rogue waves almost exactly.”

While ocean waves can differ from other waveforms, the research team gained important insights from the optical community and the study of how light waves interact.
“These are fascinating results,” said John Dudley, a professor at the Institut FEMTO-ST CNRS-Université de Franche-Comté.
“There are many different effects that can cause wave amplification, but it is essential as a scientist to keep an open mind and to keep looking for new possible explanations. It is not for us to tell Nature how to work – we must follow where it leads us, even if it means changing our ideas.”

The research has been the basis for a new rogue wave model that could be used to identify ocean areas where nonlinear effects could give rise to the waves and to provide new insights into the unsolved problem of wave breaking.
That could give shipping companies and others as much as an hour’s warning to avoid those areas.

In the end, Fedele said, the formation of the rogue wave is simply chance: the rare combination of waves in what turns out to be a bad place for ships or oil platforms.
“It’s just a bad day at the ocean,” he added.

In future work, Fedele hopes to apply the model to optical waves.
“What we would like to do next is show that there are wave groups in the ocean and in optics that behave in the same way,” he said.
“There is an underlying physical entity which is the wave group. We see a wave packet, a travelling group of waves that grows in amplitude to reach a maximum before it decays.”
In addition to those already mentioned, the research team included graduate student Joseph Brennan and postdoctoral researcher Sonia Ponce de Leon.

Links :

• citation : Francesco Fedele, et al., “Real world ocean rogue waves explained without the modulational instability,” (Scientific Reports, 2016). http://dx.doi.org/10.1038/srep27715

• GeoGarage blog : Rogue wave prediction tool developed / Rogue wave theory to save ships / Rogue waves captured / Science investigates freak waves / Studying and surfing the ocean's monster waves 

China’s ‘Historic Rights’ in the South China Sea: Made in America?

The Diplomat by Bill Hayton

The current understanding of “historic rights” in the South China Sea in China can be traced back to a U.S. diplomat.

In a matter of weeks, perhaps even days, an international tribunal will pass judgement on some of China’s claims in the South China Sea.
The judges could – potentially – rule that China’s “U-shaped line” is incompatible with international law.
The implications of such a ruling will shake the region.
Before they can consider this question, however, the tribunal judges must first consider whether they have the necessary jurisdiction.
Chinese officials have argued that the question of the “U-shaped line” is fundamentally a question of territory, about which the Permanent Court of Arbitration has no right to rule.
However, new research tells us that the judges should ignore such arguments.
Documents in China’s own archives prove that when Chinese officials approved the U-shaped line they never intended it to be a territorial boundary.
Other evidence suggests that it only became one because of the intervention of an American oilman in the 1990s.

Despite many claims to the contrary, China has never made an official “historic claim” to all the water within the U-shaped line.
It has asserted claims to the reefs and islands and to “surrounding” or “relevant” waters – but never spelled out their exact extent.
In May 2009, Chinese diplomats attached a map of the U-shaped line to an official submission to the United Nations Commission on the Limits of the Continental Shelf but didn’t explain its significance. Until they do, no one can be sure what it actually means.

The most coherent formulation of what it might mean comes from Dr. Wu Shicun, president of the National Institute for South China Sea Studies (an organization jointly sponsored by China’s Ministry of Foreign Affairs and Hainan Province).

 

For Wu, the U-shaped line claim contains three elements:

• sovereignty over the features within the line;
• sovereign rights and jurisdiction over water as defined by the Law of the Sea (UNCLOS);
• “historic rights” over fishing, navigation and resource development.[1]

The first two components: sovereignty claims over features (assuming that Wu is referring to rocks and islands rather than underwater reefs) and UNCLOS-based rights over waters surrounding those features are relatively uncontroversial.
China’s neighbors dispute the extent of those claims but they are at least grounded in commonly-understood international law.
The problem – for the region, for China and for the world – is the third part of Wu’s formulation.

China’s legal scholars are working hard, but they’ve yet to come up with a convincing justification for China to enjoy “historic rights” to waters up to 1,500 km away from undisputed Chinese territory.

South China Sea (1947)

New evidence suggests they shouldn’t even bother trying.

Thanks to the pioneering work of a Canadian researcher, we now know that the Chinese officials who drew the U-shaped line back in 1946-7 never meant it to be an historic claim to waters.

It was simply a cartographic device to indicate which islands China claimed in the South China Sea and which it did not. 

Christopher Chung, a PhD student at the University of Toronto, is the first person to forensically examine the archives of the official Republic of China (ROC) committee that drew the line.
He has discovered that, “On September 25, 1946, representatives of the Ministry of Foreign Affairs, Ministry of the Interior, Ministry of National Defense, and ROC Navy General Headquarters 海軍總司令部 (NHQ) convened in the Ministry of the Interior to resolve several issues pertaining to the South China Sea islands.”
In its meeting that day, the committee defined which islands China would claim, according to a “Location Sketch Map of the South China Sea Islands 南 海諸島位 置略圖” previously drawn up by cartographers in the Ministry of Interior.
This map is the very first Chinese government document to show the U-shaped line and its meaning was clear to that ROC committee: it defined “the scope of what is to be received for the purpose of receiving each of the islands of the South China Sea” (“接收南海各島應如何劃定接收範圍案”). The committee’s interest was only in the islands.
They made no mention of waters, historic or otherwise.

Nothing changed when that map was published a year and a half later.
In February 1948, the ROC formally concluded four decades of internal Chinese arguments about where its borders lay with the publication of the Atlas of Administrative Areas of the Republic of China.
The Atlas included the new official map of the South China Sea – the first public document produced by any Chinese government to include the line. Again, it was only about islands; there were no references to “historic rights.”

Nothing changed in China’s claim after the victory of the Communist revolution in 1949 either.
When Zhou Enlai, premier of the People’s Republic of China, denounced the draft Treaty of San Francisco in 1951, he talked only of islands, not waters.
The PRC’s 1958 “Declaration on the Territorial Sea” went further. While claiming a 12 nautical mile territorial sea, it explicitly noted that the islands were separated from the Chinese mainland by “the high seas.” There was no mention of “historic rights.”

 South_China_Sea_Islands_Map, 1935

 
 South_China_Sea_Islands_Map, 1947

The first maritime claims became more vague in January 1974, just before the Battle of the Paracels in which Chinese forces evicted Vietnam from the western half of those islands.[2]
On January 12 that year, the People’s Daily declared that,
“The resources of these islands and their adjacent seas also belong entirely to China.”
But this was not a historic rights claim either.
Rather it was the first sign that China understood the implications of the negotiations at the UN Convention on the Law of the Sea (UNCLOS), which had begun the year before: claims to maritime resources would be measured from coasts and islands.
In mid-1973 the Republic of Vietnam (South Vietnam) had begun to auction off the rights to offshore blocks off its southeastern coast. China wanted a piece of that action.

The PRC participated in the UNCLOS negotiations from the beginning until their end in 1982.
The final UNCLOS text, which it and all the other participants agreed to, makes no mention of “historic rights,” except in the very limited context of “historic bays” close to a country’s coast.
China ratified the Convention in 1996, again without making any mention of historic rights.

So, the ROC government didn’t claim “historic rights” in the South China Sea in 1946-8 and neither did the PRC in its 1958 decree, its 1974 statement, at the UNCLOS negotiations, or subsequently in its 1992 Law concerning Territorial Waters and Adjacent Regions.
Something changed in the 1990s, however. By the time the PRC passed its Law on the Exclusive Economic Zone and the Continental Shelf in June 1998, officials felt it necessary to include wording that, “the provisions of this Law shall not affect the historic rights enjoyed by the People’s Republic of China.”[3]
The concept of “historic rights” only entered the official Chinese lexicon in the late 1990s: but why then?

While there were many factors at work in 1990s China, one that has been overlooked is the contribution of a buccaneering oilman from Denver, Colorado.
In early 1991, Randall C. Thompson’s one-man oil company, Crestone, sealed a deal in the Philippines that opened his eyes to the potential riches of the South China Sea.
Engineers with BP advised him that “the next big play” would be around the Spratly Islands.

In April 1991, Thompson traveled to the South China Sea Institute of Oceanography in Guangzhou.
There he examined the results of Chinese seismic surveys the institute had carried out around the Spratlys since 1987.
“They showed me some structures, I got excited about it and then I did some more research,” he told me.
Thompson kept trying to persuade the Chinese to take Crestone seriously until, in February 1992, after much deliberation at the highest levels in Beijing, he finally got to pitch his proposal to the board of the China National Offshore Oil Company (CNOOC).
Thompson took along a legal advisor to precisely define the patch of seabed he wanted the rights to: Daniel J. Dzurek, the former chief of the Boundary Division of the U.S. Department of State.

It was Thompson and Dzurek who persuaded the Chinese that they could make a legal case to exploit oil fields hundreds of miles away from China, off the southern coast of Vietnam.
According to Thompson, “I used him [Dzurek] to help get validity to our concept this is Chinese waters and he strongly espoused many positions that this is Chinese waters, not Vietnamese waters based upon sovereignty of claim and historic stuff.”
Dzurek, however, plays down his role. In an email he told me that he, “never gave China any ‘boundary advice’,” but “merely helped negotiate an offshore lease.”
However in a key academic paper published after the Crestone episode, he noted that the Chinese term for the “U-shaped line” might best be translated as “traditional sea boundary line.”[4]
He seems to have accepted – and developed – the idea that China had “historic rights” in the area beyond those spelled out in UNCLOS.

At the same time, lawyers in Taiwan, not mainland China, were also trying to develop the concept of historic rights.
In 1993, the ROC government issued its South China Sea Policy Guidelines, which stated, “the South China Sea area within the historic water limit is the maritime area under the jurisdiction of the Republic of China, in which the Republic of China possesses all rights and interests.”[5]
The phrase appeared in Taiwan’s draft Territorial Sea Law, but disappeared on the bill’s second reading in the Legislative Yuan.[6]
The argument about whether or not to claim “historic rights” within the U-shaped line continues to divide Taiwanese maritime lawyers.

The concept has taken on new life in the Chinese mainland, particularly with officials such as Wu with an interest in maximizing the country’s maritime claims.
This is no mere academic argument; the “historic rights” claim is the only possible basis for China’s auctioning of oil exploration blocks along the Vietnamese coast in June 2012: they are well beyond any potential Exclusive Economic Zone that could be drawn from land features claimed by China.
It also lies behind the claims that Chinese fishing boats are operating in their “traditional fishing grounds” when they are found within Indonesia’s claimed EEZ off the Natuna Islands.
Above all it provides the basis of China’s claim to have the right to regulate navigation within the U-shaped line – and obstruct “freedom of navigation” by other countries’ ships.
This is the fundamental cause of the dispute between China and the United States in the region and the one most likely to lead their armed forces to come to blows.

The irony is that China seems prepared to risk conflict to defend a claim to “historic rights” that was first set out by an American boundary expert, and which is—at best—no more than 20 years old.
Some have called for China to clarify its claims in the South China Sea.
I argue the opposite.
Imagine if Beijing clarified the claim in what the rest of the world would regard as “the wrong way” – stating that the U-shaped line is a boundary and all the waters within it are historically China’s. China would have nailed its colors to the mast and be forced to publicly defend its position, regardless of its legal and historical ridiculousness.

China has recently begun what it says is a five year process to draw up a new maritime law.
Chinese officials and academics privately admit that there is still much confusion about what China should claim in the South China Sea and why.
Some internal lobbies – such as Hainan Province with its large fishing industry – want to press a maximalist claim.
But that claim will bring China into collision with its neighbors and the United States.
Now is the time for China’s friends to explain that such a claim not only has no basis in international law, but also no basis in China’s own history.
It is nonsense.

While that process of discussion continues, it is much better that China leave its claims vague and then quietly bring them into line with commonly-understood international law over time.
Forcing China into a corner, in a legally adversarial manner, might sound attractive but there’s a risk that it could force the outcome least desired by the rest of the world.

[1] Shicun Wu, Keyuan Zou Arbitration Concerning the South China Sea: Philippines Versus China, Routledge, 2 Mar 2016 p.132

[2] Chris P.C. Chung, Drawing the U-Shaped Line: China’s Claim in the South China Sea, 1946–1974, Modern China 1–35 (2015)

[3] Zou Keyuan, Historic Rights in International Law and in China’s Practice, Ocean Development and International Law, 32:149–168, 2001

[4] Daniel J. Dzurek, The Spratly Islands Dispute: Who’s On First? Maritime Briefing Vol. 2 No. 1, International Boundaries Research Unit, University of Durham, UK. 1996

[5] Quoted in Keyuan Zou ‘Law of the Sea in East Asia: Issues and Prospects’ Routledge, 2013 p.149

[6] Zou ibid p.47

 Links : 

• GeoGarage blog : US Department of State seeks to clarify meaning of China’s 9-dash line /
  China cracks down on politically incorrect maps / US: China failed to clarify 9-dash line with law
• Business insider : Tensions in the South China Sea explained in 18 maps

Giraglia Rolex Cup 2016 – Offshore Race Wrap Up

The 2016 Giraglia Rolex Cup offshore race organized by the Yacht Club Italiano and the Société de Saint-Tropez, set off from Saint-Tropez on 15 June.

 268 yacht participated in 64th edition.

The race was characterized by a range of weather conditions that eventually favoured the slower yachts.

While the 100 foot Magic Carpet Cubed secured line honours, it was the 36 foot French yacht Tip owned by Gilles Pages that prevailed in the battle for overall victory on corrected time.

The iconic regatta takes its name from an isolated cliff formation at the northern tip of Corsica, La Giraglia. Here stands a lighthouse, which must be rounded.

On the one hand, this lighthouse became the race’s landmark.

On the other hand, it heralds the final leg towards Genoa.

Throughout the history of the Giraglia Race, to give the endurance race its official title, various different courses have been sailed.

However, they have all had one thing in common: La Giraglia had to be rounded.

Since 1998, a 243-nautic mile route from St. Tropez to Genoa has become the established course, which sophisticated maxi yachts take on every year.

 Ile de la Giralglia (Cap Corse) with the GeoGarage platform (SHOM chart)

Shipstern Bluff : craziest wave on the planet

Ship Stern Bluff (also known as Devil's Point or simply Shippies)

is a globally-renowned big wave surfing 

location on the south eastern coast of Tasmania, Australia, on the Tasman Peninsula

with the GeoGarage platform

Eight reasons why octopuses are the geniuses of the ocean

In Port Phillip Bay during October, one of our small octopus (Octopus pallidus) lay their eggs in small caves ,bottle or old tyres.

The female stays with her eggs until they all hatch.

Over about 3 weeks I checked the progress of one female and her eggs.

This footage was the result

From BBC by Nic Fleming

Escaping from an aquarium is child's play when you are as smart as an octopus

In 2007 I was snorkelling in Dahab, Egypt, when I came face-to-face with a common octopus.
It was an intense experience.
I felt it was sizing me up, and there was an ill-defined but somehow profound communication.
Our meeting only lasted a few seconds, but I was left with an enduring impression of having encountered a great intelligence.
The experience may help explain the loud cheer I let out in April 2016, when I heard the news of Inky the octopus's great escape from the National Aquarium of New Zealand.
The lid of Inky's tank was left ajar at night, and he took advantage of this by climbing out, walking across a room to a drain opening, and squeezing down a 160ft (50m) pipe to the open ocean.
His successful bid for freedom was one more piece of evidence that octopuses are some of the most intelligent creatures on Earth.
Here are eight of our favourite octopus behaviours that illustrate just how smart these cephalopods really are.

A common octopus (Octopus vulgaris) on the move

(Credit: Brandon Cole/naturepl.com)

Intelligent design

Jennifer Mather is a comparative psychologist at the University of Lethbridge in Canada.
She has been studying octopuses since 1972.
One encounter, during field work in Bermuda in 1984, suggested to her that they were more intelligent than they were being given credit for.
Mather had watched a common octopus catch some crabs and take them back to its shelter to eat. Then it suddenly darted towards a rock about 7ft (2m) away, put it under its tentacles and took it back to its den.
The octopus did this three more times, creating a wall in front of its home. As if confident in the extra security measure, it then fell asleep behind the barrier.
Mather argues that this and other examples are evidence that octopuses are capable of foresight and sequencing of actions.
"This demonstrated to me that here was an animal with a mental image of what it wanted and one that was capable of planning," says Mather.
"It was very far removed from the automatic stimulus-response that we were used to thinking about with animals."

A veined octopus (Amphioctopus marginatus) lifting a shell

(Credit: Alex Mustard/naturepl.com)

Tooled up

Mather and her colleagues have argued that using stones to build walls could count as tool use. However others disagree, arguing that the octopuses could be acting in an instinctive rather than a calculated manner.
Then along came the veined octopuses. In 2009, Julian Finn and colleagues at the Museum Victoria in Melbourne, Australia found hard evidence that they used tools.
The octopuses were digging up discarded coconut shells from the ocean floor, cleaning them with water jets, sometimes stacking them and carrying them up to 66ft (20m) to later reassemble as a shelter.
The octopuses were filmed arranging the half-shells with the pointed ends facing down, then extending their arms over them and walking in a comic fashion along the sea floor.
Finn pointed out that this was a slow, awkward and energy-inefficient form of movement, which made them more vulnerable to predators.
He argues that the octopuses' willingness to accept these risks, in exchange for protection in the future, is conclusive evidence of genuine tool use.

A giant Pacific octopus (Enteroctopus dofleini) 

(Credit: Brandon Cole/naturepl.com)

Bend it like Inky

Play has often been seen as the preserve of animals with higher cognitive abilities.
It is hard to precisely define it, but in broad terms play is activity that does not serve an immediately useful function other than enjoyment.
After learning about the work of Lethbridge University colleague Sergio Pellis on mammalian play, Mather wondered whether octopuses play.
Working with Seattle Aquarium biologist Roland Anderson, who died in 2014, she devised an experiment.
They placed eight giant Pacific octopuses in bare tanks, and over 10 trials gave them floating plastic pill bottles to investigate.
At first the octopuses all put the bottles to their mouths, apparently to see if they were edible, then discarded them.
However, after several trials, two of them began blowing jets of water at the bottles.
The bottles were sent tumbling to the other side of their aquarium, in such a way that the existing current brought them back to the octopuses.
The researchers, who published the study in 1999, argued that this was a form of exploratory play.
"Roland phoned me and said 'he's bouncing the ball'," says Mather.
She says the octopuses were playing with the bottles.
This is similar to the way human children quickly start to play with unfamiliar objects, something psychologist Corinne Hutt highlighted several decades ago.
"If you have an octopus in any new situation, the first thing it does is it explores," says Mather.
"I think it was Hutt who said children will go from 'what does this object do?' to 'what can I do with this object'. That's what these octopuses were doing."

 An East Pacific red octopus (Octopus rubescens)

(Credit: Brandon Cole/naturepl.com)

Temperamentally tentacled

Mather and Anderson were happy to conclude that their octopuses were playing, even though only a couple of them did so.
That was because they had previously shown that octopuses have personalities.
This means that individual octopuses behave in consistent ways, which differ from their fellows.
This comes as no surprise to people who work with them.
For example, octopuses kept in aquaria are often given names, which relate to how they respond to people.
Mather and Anderson set out to measure these personality differences.
They kept 44 East Pacific red octopuses in tanks.
Every other day for two weeks, a researcher opened their tank lids and put their head close to the opening, touched the octopuses with a test tube brush, and offered them tasty crabs.
The researchers recorded 19 different responses. In a study published in 1993, they identified significant and consistent differences between individuals
 For example, some of the octopuses would usually respond passively, while others tended to be inquisitive.
"People often talk about rainforests as complex environments, but the near-shore coral reef is much more so," says Mather. "The octopus has many potential predators and a huge array of potential food, and given their varied and varying environments it makes a great deal of sense that individuals do not fit precisely into the same niche."
In a follow-up study published in 2001, they found evidence that octopuses pass their personality traits onto their offspring.
Given that they do not raise their young, this suggests their personalities are at least partly genetic.
Mather believes these variations in personality may underpin many of octopuses' advanced cognitive abilities, by allowing them to learn and adapt quickly.

A mimic octopus (Thaumoctopus mimicus) pretending to be a venomous banded sole

(Credit: Alex Mustard/naturepl.com)

Master of disguise

The evolutionary arms race has led animals to develop many devious ways to fool each other.
There are grass snakes that play dead to avoid being eaten, male fish that pretend to be female to boost their reproductive prospects, and birds that feign broken wings to lure predators away from vulnerable offspring.
Yet of all of nature's charlatans, the mimic octopus must be a leading contender for the title of "master of disguise".
Other octopuses can change the colour and texture of their skin to give predators the slip.
The mimic is the only octopus that has been observed impersonating other animals.
It can change its shape, movement and behaviour to impersonate at least 15 different species.
When travelling across sand, it can flatten its arms against its body and undulate like a venomous banded sole.
When moving through open water, it mimics a lionfish, which is also venomous.
Another trick is to put six of its arms into a hole and use the remaining two to look like a banded sea krait, a type of sea snake that is, of course, venomous.

 A common octopus (Octopus vulgaris)

(Credit: Claudio Contreras/naturepl.com)

A problem solved
Octopuses can use trial and error to find the best way to get what they want.
In work published in 2007, Mather and Anderson observed giant Pacific octopuses trying to get at the meat in different types of shellfish.
They simply broke open fragile mussels, pulled apart stronger Manila clams, and used their tongue-like radulas to drill into very strong littleneck clams.
When given a choice of the three, the octopuses favoured the mussels, presumably because they required less effort to get a meal.
The researchers then tried to confuse their subjects by wiring Manila clams shut. However, the octopuses simply switched technique.
Mather concluded that they could learn based on non-visual information.
"It told us that octopuses are problem-solvers," she says.
"They have different strategies to achieve the same ends, and they will use whichever is easiest first."

 A California two-spot octopus (Octopus bimaculoides)

(Credit: Visuals Unlimited/naturepl.com)

Mazes for molluscs

During fieldwork in Bermuda, Mather observed octopuses returning to their dens after hunting trips without retracing their outgoing routes.
They also visited different parts of their ranges one after another on subsequent hunts and days.
In a study published in 1991, she concluded that octopuses have complex memory abilities.
They can remember the values of known food locations, and information about places they have recently visited.
When animals use landmarks to help them navigate, they have to be understand the landmarks' relevance within their contexts.
This ability, known as conditional discrimination, has traditionally been seen as a form of complex learning: something only backboned "vertebrates" can do.
In work published in 2007, Jean Boal of Millersville University in Pennsylvania placed California two-spot octopuses in two different mazes.
In each case they had to travel from the middle of a brightly-lit tank to reach a dark den, an environment they preferred.
To get there they had to avoid a false burrow, which was blocked by an upside-down glass jar.
After five trial runs, most of the octopuses had learned to recognise which maze they were in and immediately headed for the correct burrow.
This, Boal concluded, meant octopuses do have conditional discrimination abilities.

 A mimic octopus (Thaumoctopus mimicus)

(Credit: Jeff Rotman/naturepl.com)

Similarly different
In many ways, octopuses' brains are rather like ours.
They have folded lobes, similar to those of vertebrate brains, which are thought to be a sign of complexity.
What's more, the electrical patterns they generate are similar to those of mammals.
Octopuses also have monocular vision, meaning they favour the vision from one eye over that from the other.
This trait tends to arise in species where the two halves of the brain have different specialisations.
It was originally considered uniquely human, and is associated with higher cognitive skills such as language.
Octopuses even store memories in a similar way to humans.
They use a process called long-term potentiation, which strengthens the links between brain cells.
These similarities are startling.
The last common ancestor of humans and octopuses lived a long time ago, probably quite early in the history of multicellular life, and was a simple animal.
That means the similarities in brain structure have evolved independently.
Even more fascinating than the similarities, however, are the differences.
More than half of an octopus's 500 million nervous system cells are in their arms.
That means the eight limbs can either act on their own or in coordination with each other.
Researchers who cut off an octopus's arm found that it recoiled when they pinched it, even after an hour detached from the rest of the octopus.
Clearly, the arms can act independently to some extent.
While the human brain can be seen as a central controller, octopus intelligence may be distributed over a network of neurons, a little bit like the internet.
If this is true, the insights octopuses offer extend way beyond their advanced cognitive and escapology abilities.
Inky and his relatives may force us to think in a new way about the nature of intelligence.

Links :

• Wired : Absurd Creature of the Week: The Beautiful Octopus Whose Sex Is All About Dismemberment
• BBC : How male octopuses avoid being eaten by hungry females
• GeoGraage blog : Squids and octopuses — the ‘weeds of the sea’ — are on the rise / Deep Discoverer discovers a very deep, ghostlike octopod / True facts about the octopus / How the freaky octopus can help us understand the human brain / Kings of camouflage