From Ed Yong:
In 1996, a loggerhead turtle called Adelita swam across 9,000 miles from Mexico to Japan, crossing the entire Pacific on her way. Wallace J. Nichols tracked this epic journey with a satellite tag. But Adelita herself had no such technology at her disposal. How did she steer a route across two oceans to find her destination?
Nathan Putman has the answer. By testing hatchling turtles in a special tank, he has found that they can use the Earth’s magnetic field as their own Global Positioning System (GPS). By sensing the field, they can work out both their latitude and longitude and head in the right direction.
By testing turtle hatchlings in a tank surrounded by magnets he could control, Putman showed turtles could sense it if he reversed the magnetic field around them and would begin heading in the opposite direction.
For more about the experiment—and how turtles can travel so far at such high stakes with just magnetism to guide them—check out the rest of Ed’s post at Not Exactly Rocket Science.
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Image: Wikimedia Commons
Leatherback turtles are the wandering type, undertaking far-flung ocean migrations of thousands of miles. What scientists who follow these long-lived creatures didn’t know, though, was just how many different routes they travel, and how far they journey before returning home. These are critical pieces of information for protecting the turtles, whose numbers are dropping. So Matthew Witt says he and his international team affixed trackers to the turtles and revealed the routes of their great sea voyages:
“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.” [The Guardian]
Gabon, in West Africa, is the home base for this largest breeding group of leatherbacks—it’s where they nest and lay their eggs. Witt’s team tracked 25 female turtles, all of whom followed one of those three general routes: out to the middle of the Atlantic and then back, down the African coast to the temperate South, or even all the way across the ocean to South America.
One female was tracked making a 7,563 kilometer (4,699 mile) journey traveling in a straight line across the South Atlantic from Africa to South America, said [Witt]. At a pace of 50 kilometers a day, that trip took about 150 days of consistent swimming, he said. [AP]
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From Ed Yong:
When Chrysoula Gubili from the University of Aberdeen compared the DNA of white sharks from around the world, she found a big surprise. The great white is the most genetically diverse shark studied so far but the Mediterranean fish are only distantly related to nearby populations in the North-West Atlantic, or even in South Africa. Their closest kin actually live half a world away in the Indo-Pacific waters of Australia and New Zealand….
Gubili thinks that the European population was set up by a single founding female who got lost. Female great whites undergo long migrations of thousands of kilometres, but they tend to return to the place where they were born. However, it’s possible that some individuals lose the bearings on these monster treks. These navigational problems rarely amount to anything. But if the wayward female is pregnant, she might end up setting up an entirely new splinter group in a far-off corner of the world.
Read the rest of this post at DISCOVER blog Not Exactly Rocket Science.
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Image: flickr / hermanusbackpackers
You know the “out of Africa” story: how our ancestors left the savannas where humanity grew up and trekked outward to other continents. Today in Nature, however, a new study of 40 million-year-old fossils argues that an “into Africa” story predates the other narrative: that the animals that would eventually evolve into apes like us and monkeys came from Asia into Africa.
These fossil teeth found in Libya belong to early anthropoids, according to the scientists. The team found several different species in this location.
The new fossils are about 38 to 39 million years old, and none of the animals would have weighed more than 500 grams [just more than 1 pound], conclude a team led by Jean-Jacques Jaeger, a palaeontologist at the University of Poiters, France. Their diminutive size fits in with previous research suggesting that early anthropoids started small and eventually evolved ever bigger bodies. [Nature]
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From Ed Yong:
On 7 August 1999, a lucky photographer snapped a female humpback whale frolicking off the east coast of Brazil. Two years later, on 21 September 2001, the same whale was caught on camera again, by a tourist on a whale-watching boat. But this time, she was a quarter of the world away, off the eastern coast of Madagascar. The two places where she was spotted are at least 9800 kilometres apart, making her voyage the longest of any mammal.
In American terms, that means the adventurous humpback had taken a trip of about 6,000 miles. Read the rest of the post–including info about how scientists are sure they were looking at the same whale both times–at Not Exactly Rocket Science.
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Image: iStockphoto
Two weeks ago we covered the dust-up between eco-groups and the government of Tanzania over the latter’s proposal to build a road through the heart of Serengeti National Park, home to the world-famous annual migrations of wildebeests, zebras, and more. Today in Nature, a group of 27 scientists chimed in on the project. Their verdict: It would be a biodiversity disaster.
Conservationists led by Princeton’s Andrew Dobson … argue the planned 2012 road would stop the yearly migration of 1.3 million wildebeests, the cornerstone species of the park, and harm other animals such as the 1.5 million zebras that yearly migrate as well. [USA Today]
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Government and big business try to build a massive industrial project in a protected space. Wildlife defenders rise up to save the threatened reserve. This starkly drawn plot line sounds like the simplistic basis of a hundred Disney films, but in this case the drama is playing out for real in Tanzania.
The government of Tanzania would like to build a highway that connects the commercial activity on the country’s coastal eastern side to the inland and more remote west. That highway, however, would cut right through the plains of Serengeti National Park, and right through the annual migratory path of the millions of gazelles, zebras, and wildebeests that head from Tanzania to Kenya and provide a gorgeous visual staple for nature films.
Groups like the Wildlife Conservation Society (WCS) and Zoological Society of London have raised their voices to oppose the project.
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Crocodiles like to lurk in the shallows, preparing to pounce. They are not, as a general rule, strong enough swimmers to go on extended ocean cruises whenever they feel like it. Despite this, these creatures managed to reach islands across the South Pacific. How?
Surfing.
A group of scientists led by Craig Franklin, and including the late “Crocodile Hunter” Steve Irwin, studied saltwater crocs from the Kennedy River area of Northeastern Australia for about a year for a study forthcoming in the Journal of Animal Ecology. The team tagged 20 animals with receivers to give both their position and body temperature.
They found that eight crocodiles undertook a total of 42 long-distance journeys of more than 10 kilometres [6.2 miles] per day. In 96% of these trips, the reptiles traveled with the current flow. In contrast, the crocodiles were equally likely to travel with and against the current flow when making short journeys [Nature].
The body temperature reading gave the scientists another way to verify this, besides matching croc travel habits to changing ocean currents. When the tide went against the crocs, they just hung out on the beach and their body temperature rose to 90 degrees F as they soaked up the sun. However, when the current became favorable and they went traveling, their temperatures descended to more like 77 degrees.
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The single-mindedness that drives a swarm of locusts to rampage through the countryside and devour everything in its path might not seem like it would require a great deal of brainpower. However, biologists in Britain have found that the brain of a swarming locust swells up to 30 percent larger than the brain of its solitary counterparts.
These crazed grasshoppers aren’t geniuses, says lead researcher Swidbert Ott. According to his study forthcoming in the Proceedings of the Royal Society B, swarming locusts simply need enlarged brains to cope with the assault on their senses that comes with being caught up in an insect mob:
Locust brains are quite simple: on each side of the head is an optic lobe taking in information from the eyes and performing basic processing, and these lobes feed into the central midbrain, which carries out higher-level processing.
In swarming locusts, the midbrain grew more than the optic lobes. This, and other subtle changes, suggest that because swarming locusts are constantly surrounded by wild activity, they do not need to worry about having particularly sensitive vision. However, they do need extra high-level processing power to cope with the extremely complex patterns of motion that they see [New Scientist].
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Some of the weird wildlife on Madagascar—its mammals especially—probably arrived there by rafting from mainland Africa, we reported back in January. But not its blind snakes. According to a study out now in Biology Letters, these funny-looking creatures date back 150 million years to the Gondwana landmass, and have lived on Madagascar since before it broke off from India and drifted away. And, the researchers say, their story of spreading around the world carries many more twists.
Growing to about a foot long, blind snakes act a lot like worms, burrowing under the surface of every continent except Antarctica. Unlike worms, though, blind snakes have backbones and tiny scales [National Geographic]. They earned their moniker by having blurry vision and sensing chemicals through their skin to find their way around. But despite having backbones, there are few blind snakes in the fossil record, making it hard for researchers to study their evolutionary history. So lead researchers Blair Hedges and Nicolas Vidal had to rely on living species. They extracted five nuclear genes, which code for proteins, from 96 different species of worm-like snakes to reconstruct the branching pattern of their evolution, allowing the team to estimate the times of divergence of different lineages using molecular clocks [UPI].
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Life: Ain’t it grand?
That seems to have been the starting point for the new nature documentary series LIFE, which spotlights some of the planet’s most gloriously unusual critters. The series, which airs on Sunday evenings on the Discovery Channel, presents animals that belong in the evolution hall of fame. Many have developed remarkable tricks to survive in inhospitable environments, while others have developed fascinating mating rituals that ensure that the fittest individuals pass on their genes, generation after generation.
Click through the gallery for some of our favorite hall-of-famers from the show.
A Restless Trail-Runner
Size does matter, especially for the tiny rufous sengi, an “elephant shrew” whose small size and constant movement makes it hungry—all the time! But movement in a forest full of predators is dangerous, so the sengi devised a clever method to forage for food.
The tiny mammal constructs a series of neatly cleared trails between its regular feeding spots and memorizes their details. Then it launches itself on a trail patrol at breakneck speed, stopping only to check for tasty insects and to clear the trail of any debris. A single twig can be fatal, so the sengi spends up to 40 percent of its time running the trails and clearing away obstacles.
Just how did all the exotic mammals of Madagascar, like its unique collection of lemurs, originally reach the African island? Did they float there from the African mainland, or did nature provide a land bridge? The question has vexed biologists because both explanations have their problems. But a new study in Nature proposes an answer to the main problem posed by the floating-across-the-channel idea, suggesting that it is the most likely explanation.
Because of the narrow range of biology on Madagascar, most biologists favored the floating rafts hypothesis. But there has always been a problem with this notion: the currents swirling in the channel and the surrounding Indian Ocean would make it virtually impossible for a floating Noah’s Ark of vegetation to reach Madagascar’s shores [AFP]. Were those currents always this way, though? No, says a team led by Matthew Huber.
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If you thought George Clooney’s character in “Up in the Air” racked up a lot of frequent flyer miles, you should meet his avian rival, which flies the equivalent of three round trips to the moon and back during its lifespan. For a study in the Proceedings of the National Academy of Sciences, researchers tracked the arduous migration of the tiny Arctic tern and found that it flies an average of 44,000 miles every year on its trip from Greenland to Antarctica and back. That’s a new world record.
Scientists suspected that this tern could best the previous world record of 39,000-mile migrations by the sooty shearwater, though they previously lacked tracking devices small enough for the bird to carry. But the team used a tiny tracker developed by the British Antarctic Survey, which weighs just a twentieth of an ounce (1.4 grams)—light enough for an Arctic tern to carry on a band around its leg [National Geographic]. This device reported the birds’ position twice daily.
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Sixty-five million years ago—we know when the dinosaur story ends. But the beginning of the dinosaur age is hazier, due to the small number of distinct fossils with which to set a time frame. But now scientists have turned up fossils in New Mexico of an early dinosaur ancestor, they report tomorrow in the journal Science, one that points to South America as the possible place of dinosaur origin.
The feathered beast, named Tawa hallae, was the size of a large dog and sported a long neck and tail, a slender snout, and sharp, curved teeth to catch and kill its prey [The Guardian]. Tawa hallae is an early theropod, meaning it is related to birds and the mighty T. Rex.
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Today it’s tempting to think of Antarctica as an icy wasteland, hospitable for penguins and seals but not much else. However, before the continent was covered by a permanent ice sheet, it may have been a refuge from a world in chaos, according to findings published in a journal called Naturwissenschaften.
Jörg Fröbisch of Chicago’s Field Museum says that a distant relative of mammals, a cat-sized herbivore called Kombuisia antarctica survived the Permian-Triassic Extinction 250 million years ago by migrating from southern Africa to Antarctica. At the time of the end-Permian extinction, Antarctica was some distance north of its present location, warmer than it is today, and not covered with permanent glaciers [The Telegraph].
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