Secret voyages of leatherback turtles revealed using transmitters

Researchers were able to follow the journey leatherback turtles make from Africa to the South American coast using transmitters

From TheGuardian

Researchers have tracked 'nature's ancient mariners' as they spend several months travelling from Africa to South America

On 2 February 2009, at 4am, a turtle known as Tika set off from the coast of Gabon, west Africa. She spent almost six months swimming across the Atlantic, a 5,000-mile (8,000km) journey to the coast of South America.
At the moment she is probably somewhere off Brazil, eating jellyfish and building herself up.
In about March next year, she'll begin her journey back to Africa, and, if all goes well, she'll then build a nest and lay her eggs in the sands of the Mayumba national park in Gabon.
And this will be just one of many 10,000-mile round trips she makes in her 50-year life.

Scientists know all of this because, for the first time, they have tracked the journeys taken by leatherback turtles as they cross the Atlantic Ocean, with Tika travelling the furthest of the 25 females that were followed in a study lasting more than five years.
She, along with another female called Regab, ended up in the waters off Brazil, Argentina and Uruguay.
Others stayed closer to Africa, but still their journeys lasted for months and they swam thousands of miles.
One, named Caroline by researchers, swam around the middle of the Atlantic for more than a year and a half, clocking up more than 7,000 miles, before returning to breed.

The maps of their journeys, published today in the Proceedings of the Royal Society B, will be an important means by which to document and conserve the rare creatures in the Atlantic Ocean, according to the scientists involved.
In the Pacific, numbers of leatherback turtles have plummeted in the past few decades, as they are caught and drowned in fishing nets.

Matthew Witt, a researcher at the Centre for Ecology and Conservation at the University of Exeter, led the project.
"Despite extensive research carried out on leatherbacks, no one has really been sure about the journeys they take in the south Atlantic until now," he said.

"What we've shown is that there are three clear migration routes as they head back to feeding grounds after breeding in Gabon, although the numbers adopting each strategy varied each year. We don't know what influences that choice yet, but we do know these are truly remarkable journeys – with one female tracked for thousands of miles travelling in a straight line right across the Atlantic."

Each turtle was fitted with a simple transmitter on her back, powered by four lithium camera batteries.
This sent signals to a satellite receiver every time the creature came up for air on its travels across the open ocean.

The data showed that Regab took 150 days to swim 4215 miles, arriving in the waters off Brazil.
The deepest dive was 1,080 metres, by a turtle called Darwinia, who was also headed to South America.

As well as South America, Witt's team identified two other migration routes.
One saw turtles swim to the coast of South Africa, while the other led them around the middle of Atlantic Ocean.
"Although sometimes they're in the middle of nowhere, hundreds of kilometres from any coastal features, they have plonked themselves in the middle of a food hotspot," said Witt.

In each case, the turtles swim thousands of miles to stay within food-rich areas of the oceans. Typically, a mature individual could stay swimming around the migration routes for up to five years, building up food reserves, before returning to their birthplace in Gabon to reproduce.

The data from the research project will be used to try to prevent the potential decline of leatherback turtles.
"If you look at the Pacific Ocean, the population there has undergone a huge decline – greater than 98% [have gone] in 30 to 40 years," said Witt.
"The population is bordering on extinction; there are only hundreds of females left, rather than many tens of thousands."

The exact cause of the dramatic fall in Pacific numbers is not clear, but turtles can get caught on the hooks used to catch tuna, or under large gillnets.
In both cases, the turtles are held under the water and drown.
"It's all accidental bycatch, but it still has really significant impact on the population," said Witt. "The one risk that doesn't seem to exist in central Africa is egg-harvesting. This is a good thing because you can just keep refreshing the populations with the females and the new eggs they lay."

Banning fishing in the areas where turtles live is not always necessary, said Witt.
"There are a whole range of strategies people have been developing over the last five to 10 years, such as changing the shape of hooks, changing the colour of the glowsticks and changing the bait types. It still maintains fisheries' catch rates, but it reduces sea turtle bycatch."

Brendan Godley, of the University of Exeter and a co-author of the work, said all of the routes identified by researchers take the leatherbacks through areas at high risk from fisheries, so there was a real danger to the Atlantic population.

"Knowing the routes has also helped us identify at least 11 nations who should be involved in conservation efforts, as well as those with long-distance fishing fleets.
There's a concern that the turtles we tracked spent a long time on the high seas, where it's very difficult to implement and manage conservation efforts, but hopefully this research will help inform future efforts to safeguard these fantastic creatures."

Howard Rosenbaum, director of the Wildlife Conservation Society's Ocean Giants programme, agreed.
"This important work shows that protecting leatherback turtles – the ancient mariners of our oceans – requires research and conservation on important nesting beaches, foraging areas and important areas of the high seas.

"Armed with a better understanding of migration patterns and preferences for particular areas of the ocean, the conservation community can now work toward protecting leatherbacks at sea, which has been previously difficult."

All at sea

Leatherbacks are born on the beach and, in the case of those in the Atlantic, that means somewhere along the coast of southern Gabon in the Mayumba national park.
Hatchlings run straight into the sea and spend their first few years being wafted around the dominant ocean currents, not yet strong enough to swim as they please.

"While you're a hatchling and growing over the first five to 10 years, you're just being swept along the south Atlantic," said Matthew Witt, of the University of Exeter.
"Once you get to a stage where you can maintain your own position and be a bit more autonomous, that might become your foraging ground as an adult."

Leatherbacks prey on jellyfish and other soft-bodied sea creatures, and can live for 40 to 50 years.
When turtles reach sexual maturity about 10 to 15 years after they have been hatched, they swim back to their birthplace to reproduce.
Male turtles stay in the water all their lives, unlike females, which head towards land when they are fertilised.

Females can mate every year and, in each clutch, will lay about 100 eggs in the sand of a beach near their own birthplace. These will hatch within 70 days.
"To generalise, all leatherbacks in the south Atlantic typically come from central and West African beaches," said Witt.
"Most nesting of leatherbacks happens in Gabon on those central west African beaches."

Because they live predominantly in the open ocean, there is little opportunity to see the young individuals and plot out their journeysas juveniles.
Witt's research has created a live map of creatures around the Atlantic, updated at www.seaturtle.org.

Links :

• TheTelegraph : Turtles' cross ocean navigation tracked
• BBCNews : Tracking a turtle's extraordinary journey / Leatherback turtles tracked on Atlantic 'danger' trips
  
• OurAmazingPlanet : Tracking a mysterious giant, first look at epic turtle migrations
• DiscoveryNews : Turtle's epic, perilous journeys documented
• NationalGeographic : Turtles need protected sea lanes, conservationists urge
  

Cretan tools point to 130,000-year-old sea travel

This undated hand out photo provided by the Greek Culture Ministry shows four Early Stone Age axes discovered by a US-Greek team of archaeologists on the southern island of Crete.
A ministry statement that these and other similar finds, dating back at least 130,000 years, point to what may be one of the earliest signs of human seafaring.

From NPR

Archaeologists on the island of Crete have discovered what may be evidence of one of the world's first sea voyages by human ancestors, the Greek Culture Ministry said Monday.
A ministry statement said experts from Greece and the U.S. have found rough axes and other tools thought to be between 130,000 and 700,000 years old close to shelters on the island's south coast.

Crete has been separated from the mainland for about five million years, so whoever made the tools must have traveled there by sea (a distance of at least 40 miles).
That would upset the current view that human ancestors migrated to Europe from Africa by land alone.

"The results of the survey not only provide evidence of sea voyages in the Mediterranean tens of thousands of years earlier than we were aware of so far, but also change our understanding of early hominids' cognitive abilities," the ministry statement said.

The previous earliest evidence of open-sea travel in Greece dates back 11,000 years (worldwide, about 60,000 years — although considerably earlier dates have been proposed).

The tools were found during a survey of caves and rock shelters near the village of Plakias by archaeologists from the American School of Classical Studies (ASCSA) at Athens and the Culture Ministry.

Such rough stone implements are associated with Heidelberg Man and Homo Erectus, extinct precursors of the modern human race, which evolved from Africa about 200,000 years ago.

"Up to now we had no proof of Early Stone Age presence on Crete," said senior ministry archaeologist Maria Vlazaki, who was not involved in the survey.
She said it was unclear where the hominids had sailed from, or whether the settlements were permanent.

"They may have come from Africa or from the east," she said.
"Future study should help."

The team of archaeologists has applied for permission to conduct a more thorough excavation of the area, which Greek authorities are expected to approve later this year.

Links :

• NationalGeographic : Primitive humans conquered sea, surprising finds suggest
• BostonUniversity : Riding the waves, 130,000 years ago
  

Image of the week : tidal flats and channels, Long Island, Bahamas

Astronaut photography acquired on November 27, 2010 by Expedition 26 crew

From NASA

The islands of the Bahamas are situated on large depositional platforms—the Great and Little Bahama Banks—composed mainly of carbonate sediments ringed by reefs.
The islands are the only parts of the platform currently exposed above sea level.
The sediments were formed mostly from the skeletal remains of organisms settling to the sea floor; over geologic time, these sediments consolidated to form carbonate sedimentary rocks such as limestone.

This astronaut photograph provides a view of tidal flats and channels near Sandy Cay, on the western side of Long Island and along the eastern margin of the Great Bahama Bank.

-> Location with the Marine GeoGarage and Bahamas nautical charts layer

The continuously exposed parts of the island are brown, a result of soil formation and vegetation growth.
To the north of Sandy Cay, an off-white tidal flat composed of carbonate sediments is visible; light blue-green regions indicate shallow water on the tidal flat.
The tidal flow of seawater is concentrated through gaps in the land surface, leading to the formation of relatively deep channels that cut into the sediments.
The channels and areas to the south of the island have a vivid blue color that indicates deeper water.

'Iceberg cowboy' finds archway in the middle of ocean

A strange sight greeted biologists recently:
an iceberg archway, floating in the middle of the Atlantic Ocean.

From FoxNews

Forget moving mountains.
Marine biologist Andrew Perry moves icebergs.
And his latest adventure led to the discovery of an icy archway, right in the middle of the ocean.
Perry was out trawling for icebergs with Oceans Limited, a Canadian company that identifies which of the tremendous floaters are drifting towards stationary deep-water oil rigs, when he found the arch -- think Stargate meets portal to Narnia.

"It was a beautiful day, hardly a wave on the water. And then there it was -- a big beautiful arch," Perry told.
"No one had seen anything like this. We thought it was amazing."
Icebergs routinely break off Greenland and float down the Labrador coast, Perry explained, a corridor he called "iceberg alley".
Along the way, they post a direct threat to deep-water oil installations.
Though they don't move particularly quickly -- typically one to four knots -- they've got enough bulk to do major damage if they hit anything, he explained.
"We recorded some upwards of 350,000 tons" Perry said.
Oceans Limited moves smaller icebergs by training water cannons on them for hours.
"That's for the smaller ones, we call them growlers".
It's much cheaper to move the icebergs, even the very large ones, than to disconnect the oil rig and move it, he pointed out: moving a rig costs millions, while operating a small boat costs about $25,000 per day.

So Perry's company either lassos the big boys with a single boat or corrals them with a net dragged between two boats.
Icebergs don't move particularly fast, Perry explained, so changing their course can take quite a while, but they don't have to move too many each year.

"Depending on the ice season, they may have to tow 10 to 20 ... during the 2009 season we profiled around 60 icebergs to get computer generated 3D images," Perry said.
But he had never run into an iceberg like this one before.
Icebergs are often seen as just giant chunks of compressed water, not stunning works of natural art.
Yet beautifully sculpted icebergs like the one Perry found are actually fairly common, thanks to the natural forces of the seas and the skies, explained Ted Scambos, lead scientist for the National Snow and Ice Data Center (NSIDC) at the University of Colorado in Boulder.
"Complex, sculptured icebergs like this are usually formed from ice that broke off of fast-flowing glaciers," Scambos said.
"It starts off as a rugged piece of ice that waves and sunshine then sculpt."
Sure, but how did this iceberg form in such a stunning fashion?
Wave action, Scambos explained, and it's more common than you might think.
"As the waves begin to pound out a dimple in the ice facewall, it focuses the wave energy, leading to more rapid erosion at the center.
So, with time, the waves carve through the face to the other side.
"It's not the first one I've seen, but it's the most artistic."
Icebergs are surprisingly noisy as well, according to Perry. They're constantly moving and cracking, he said. The arch "sounded like shotguns being fired off all the time, due to the ice cracking."

And what to do with all of that ice?
Perry and his fellow biologists have a unique use for icebergs: they put them in cocktails.
"To be honest it's the cleanest water you can get. The air bubbles trapped in it are under so much pressure the ice fizzes when it melts."
"Who doesn't want 500,000-year-old ice in their drink?" he joked.

Happy New Year 2011

2011 is a prime number.

So this year will be a prime year.
What to wish, then ?
A sea of love and love of the sea.