Field of Science


11 People Trace Synesthesia to One Set of Alphabet Magnets
















Images: Manon Paradis (Flickr); Witthoft & Winawer.

How to Cross the Deep Sea: Stepping Stones of Mollusk Poop

The seafloor has no shortage of spiky wildlife or hairy mysteries. One such mystery is logistical: where do the animals that live around deep-sea vents and cold seeps come from?

On the black and generally barren bottom of the ocean, food is scarce. Hydrothermal vents and cold seeps—places where methane, sulfides and other chemical goodies leak out of the seafloor—are like desert oases. Whole communities of weird creatures that live on these chemicals rather than the sun cluster around them.

Researchers think big pieces of organic junk that fall to the bottom of the ocean, such as sunken ships and deceased whales (called "whale falls"), may act as stepping stones for these communities. Species might disperse from one seafloor chimney to the next via a visit to a wrecked ship.

"Wood is a foreign substance in the deep sea," says Christina Bienhold of the Max Planck Institute. To find out whether resourceful ocean critters can easily make use of wood that falls into the ocean, she and other researchers dropped some in. They rigged together small heaps of Douglas fir logs, weighted them with cement, and carried them a mile down into the Mediterranean.

The researchers used four wood piles, each two meters long. They were at various distances from a known cold seep. The closest log was 70 meters away—so if any animals scooted over from that community, it would be a bit of a trek.

One of the wood heaps was sampled just one day later. (It looked the same.) The other three rested on the ocean floor for a year before robotic vehicles returned to collect wood samples and scoop up the animals that had moved in.

And did they ever move in. Bienhold was surprised to find that her logs, after only a year on the seafloor, held thriving colonies of wildlife.

The logs' most abundant tenants were wood-boring bivalves called Xylophaga, or "shipworms." Built like a worm with a shell on one end, these mollusks burrow into wood while symbiotic bacteria help them digest it. All around the logs were evidence of their work: the researchers observed a layer of "fine wood chips and fecal matter" two to four centimeters thick.

The shipworms seemed to have attracted other animals interested in feeding on the mollusks themselves or on the waste piles they left everywhere. As these creatures ate and respired, they used up oxygen in the water and allowed oxygen-hating bacteria to move in. These bacteria created pockets of sulfides—food for the kinds of animals that live at cold seeps or hydrothermal vents. (Normally, they would find this food coming straight out of the ground.)

Like very unattractive doves out of a hat, those animals began to materialize out of the blackness of the ocean. Clustered around the logs were sea urchins, fish, and deep-sea mussels and crabs. There were small crustaceans that couldn't be identified, and several types of worms, including two brand-new species.

All three wood piles had similar animal communities living on and around (and, in the case of the crabs, hiding underneath) them. Their bacterial communities were more diverse. But they all included bacteria that could break down the cellulose in wood, as well as bacteria that consume sulfate instead of oxygen.

Bienhold says her results show how wood that falls to the seafloor can create hotspots of ocean life. Hunks of organic trash like her log piles, even though they're few and far between on the bottom of the ocean, could help rare deep-sea species to spread. The key player in her set of experiments was the little wood-boring bivalve that moved in first and made the logs into a habitat that other wildlife could use.

"It remains enigmatic," Bienhold says, how the wood-borers (or any of the other organisms) found this new habitat in the first place. The researchers observed a greater density of sea urchins as they got closer to the wood piles; they seemed to be attracted to the wood by some chemical signal. Sea urchins and other animals may sniff out chemical cues from afar that help them find organic matter. For now, though, the secret remains sealed in their lipless bodies.

Bienhold C, Pop Ristova P, Wenzhöfer F, Dittmar T, & Boetius A (2013). How deep-sea wood falls sustain chemosynthetic life. PloS one, 8 (1) PMID: 23301092

In Our Partners' Heights, We Get What We Want













Image: Peter Rukavina (Flickr)

This Penguin: An Unexpected Journey

The humble king penguin chick had no way of knowing, when it woke up that day, that tall creatures from far away would come to send it on a journey. Nor could it know that its journey would become the subject of a manuscript read and studied by many. (It still doesn't know that part, because it's a bird.) 

When the humans came, the penguin was in its crèche, a cluster of young birds left behind while their parents foraged. Other penguins young and old stretched away from it in all directions. All at once, the chick was lifted from the ground by a pair of human hands. A cloth hood was pulled over its head. The researcher spun the bird around three times, then set off, carrying the bird away from the colony at a fast clip. 

Human and penguin traveled a circuitous route meant to further disorient the bird. When they reached their destination, the human spun the penguin three more times. Finally the chick found itself on solid ground, the hood pulled away from its eyes. Its colony was nowhere in sight.

The penguin was standing inside a circular arena about 10 meters across, surrounded by a meter-high wall of cloth. A scientist quickly fitted a pair of pads, like earmuffs, over the chick's head, deadening the sounds it heard. Then the penguin was left alone.

For fifteen minutes, following cues in its head that were inscrutable to the human observers, the penguin wandered inside the arena. Its instincts told it to return to the crèche right away, so its parents could find it when they came back. While it tried to discover the right direction, human eyes watched and recorded. Finally the walls of the arena came down; the bird was free to go.

It set off waddling across the frozen ground, still wearing its earmuffs. The bird was less than 200 meters from the colony but still couldn't see it. The ocean, though, was in sight. The chick walked straight to the shore. Then it hung a left and headed, correctly, for its colony. Finally it reached the crèche and the other chicks it had left behind. A piece of wood was on the ground, left by the human to mark the spot where the penguin had stood before its abduction.

This traveler was only one of many young penguins the humans lifted from their crèches in those days. Some, instead of earmuffs, had magnets temporarily attached to the backs of their heads. Some were made to travel by night. Some heard a recording of the colony broadcast loudly from speakers within the arena.

The researchers, who came from the University of Oxford and the CEFE in France, hoped to learn from the journeying birds the secrets of penguin navigation. Earlier visits to penguin crèches had told them that the young birds navigate partly by sight, but that most of them could still find their way in the dark—so some other talent was at work too.

Chicks with magnets on their heads did not fare any worse than usual. This revealed to the humans that the penguins didn't rely on sensing the earth's magnetic fields (as homing pigeons are able to do). 

The 18 earmuffed birds were also just as likely to navigate home as non-earmuffed birds. But out of the 16 who made it home without help, researchers noticed that 6 took an unusual path. Like our hero, they seemed to orient themselves by first walking to the ocean, then following it back. It was an intriguing hint that the earmuffs, which quieted the sound of the squawking penguin colony but didn't block it out entirely, were changing the birds' navigation strategy.

The second experiment involving sound truly befuddled the young birds. When speakers inside the arena played the sounds of the colony, almost all the penguins oriented themselves toward the speakers instead of toward home (in the opposite direction). Several chicks stood in front of the speakers, calling to them plaintively.

Five minutes after the walls came down, nearly all the undisturbed chicks were well on their way back to the colony. But many of the chicks who had heard the speaker noises lingered close to the arena. A few set off in the wrong direction entirely. 

The humans made sure all the young birds made it back to their crèches in the end. Afterward, lead author Anna Nesterova told the tale of the traveling penguins in the Journal of Experimental Biology.

From her story, Nesterova drew the moral that penguins use acoustic cues as part of their navigational toolkit. The sound of the distant colony seems to call them back. But the visual landmarks around the birds are also important, and there may be other clues they take in as well. 

As adults, king penguins must navigate between the colony (which may span several kilometers) and their foraging grounds. Upon returning to the colony, they find their partners and chicks by calling out and listening for the right voices among thousands—a task that would seem to require magic. Someday, we meddling humans may learn the secret of how these birds get there and back again.

Nesterova, A., Chiffard, J., Couchoux, C., & Bonadonna, F. (2013). The invisible cues that guide king penguin chicks home. The use of magnetic and acoustic cues during orientation and short-range navigation Journal of Experimental Biology DOI: 10.1242/jeb.075564

Images courtesy of Anna Nesterova.

The Shambulance: Enough Already with the Juice Cleanses

















Image: Food Thinkers (via Flickr)

Captive Animals Act Smarter

In the Kenyan wilderness, hyenas facing a meat-stuffed puzzle box performed impressively—impressively badly, that is. Researchers expected the animals to be up to the challenge, but few of them ever got the box open. Now, repeating the experiment with captive hyenas, they've discovered that there's no contest: the captive animals are better problem solvers.

Out of 62 wild hyenas in last year's study, less than 15 percent ever managed to slide the latch and swing open the door of the barred metal box. Despite multiple chances, most of the animals were losers in this game.

But lead author Sarah Benson-Amram observed certain behavioral traits shared by the winners. Hyenas that tried more techniques to get the box open (biting, dragging, flipping the darn thing over) had greater odds of success. And hyenas that were less "neophobic"—that is, less wary when approaching a new object in their environment—also did better.

Previous studies with primates and birds had suggested that captive animals are both less neophobic and better at problem solving than wild ones. So Benson-Amram repeated her experiment on a group of hyenas living very far from their homeland, in Berkeley, California.

This group was smaller than the wild hyena group, with only 19 animals tested. But three-quarters of them solved the puzzle, Benson-Amram reports in Animal Behaviour. And every successful captive hyena got the meat on its first try—unlike the wild animals, most of which needed more than one trial before they figured it out.

Although the wild and captive animals belonged to the same species, you would get very different impressions of hyenas' problem-solving smarts if you only looked at one group.

Benson-Amram ruled out a few possible explanations for that difference. Did well-fed animals have more energy for solving the puzzle? In the wild, high-ranking hyenas ate more but didn't do any better with the puzzle box. Were hungrier animals more motivated? Skinny hyenas had no advantage either, and captive hyenas didn't lose interest after eating.

Two explanations, though, held up. One was neophobia. In the wild, animals that were more cautious about approaching the manmade box were less likely to crack it open. Captive animals were overall less neophobic than wild ones. This isn't surprising, since they're used to living around humans and our metal objects.

The second notable difference was that captive hyenas tended to try more behaviors (biting, digging, pulling, and so on) than wild hyenas did. Benson-Amram thinks this has to do with distraction.

"It’s almost akin to giving a puzzle to a civilian in an active war zone versus giving one to a person in the comfort of their living room," she says. The wild hyena is busy watching out for predators, rather than wondering whether pushing and biting at the same time might get this box open. "The person in the war zone would likely give much less mental focus to the puzzle since they have to constantly look over their shoulder," Benson-Amram says.

Or maybe the comfortable home isn't the right analogy for the captive hyenas.

"Imagine giving a puzzle to a person in solitary confinement," Benson-Amram says. "That person may be much more excited about the puzzle and interested in solving it than the person in their living room who has TV, books, their family, and other fun diversions." She adds, "I am not trying to say that zoos are as bad as solitary confinement." But captive hyenas clearly live in a more predictable, less stimulating environment than the Kenyan savannah.

Not all the hyenas learned how to open the box. But scientists learned something that might be critical. When researchers are wondering about the "maximum cognitive abilities" of a species, Benson-Amram says, captive animals may be better subjects. When they want to know what a species is capable of in the wild, though, they should remember that it's a war zone out there.

Benson-Amram, S., Weldele, M., & Holekamp, K. (2012). A comparison of innovative problem-solving abilities between wild and captive spotted hyaenas, Crocuta crocuta Animal Behaviour DOI: 10.1016/j.anbehav.2012.11.003

Image and video courtesy of MSU.

Why Humans Prefer Not to Gallop

As kids, we discover that our two legs can manage many different gaits. After walking and running we figure out how to tiptoe, hop, and skip. (Personally, I decided at one point to become a better skipper than anyone I knew, practicing backward skipping and figure-eights in our driveway. I may have sensed that my competition in this pursuit was not very stiff.)

For basic getting around, we usually settle on walking and running. But why do we ignore so much of our bipedal repertoire in favor of locomotion that's more, well, pedestrian? Researchers in Belgium asked this question about one gait in particular: the gallop.

In case you missed this one as a kid, the human version of a gallop involves holding one leg always in front of the body and the other leg always behind. Bounding along, you create an uneven rhythm of footfalls: ba-DUM, ba-DUM, ba-DUM.

"Gallop is, though rarely used, a familiar gait for humans," the authors write in the Journal of Experimental Biology. People may start galloping spontaneously under certain (infrequent) circumstances, such as going quickly downhill.

For their study, lead author Pieter Fiers of the University of Antwerp and his colleagues had a dozen volunteers run and gallop down a hallway, then dissected their motion in great detail. Platforms that lined the hallway measured the force people produced in their steps. The subjects were covered in motion-capture markers, like Avatar actors. Finally, a separate group of subjects did their running and galloping on a treadmill while the researchers measured how much oxygen they used and carbon dioxide they gave off.

People preferred to gallop at pretty much the same speed they ran. But the length of a galloping stride was shorter than a running stride—so gallopers had to take more steps, and do more work, to travel at the same speed as runners.

Gallopers exerted that effort unevenly, with the front leg doing more work than the back leg. And the galloping stride, researchers saw, demanded more from the hips than running did. This tired people out quickly. Out of 12 treadmill gallopers in the study, 4 gave up before the end of their 4-minute session, complaining of fatigue and stress in their hips and thighs. (An intended 13th galloper couldn't figure out how to gallop on the treadmill belt in the first place.)

When researchers calculated their subjects' metabolic rates, they found that galloping was about 24% more costly than running at the same speed. In other words, galloping burns up more energy, takes more effort, and is less comfortable than running. It's no wonder we don't usually opt for it.

Still, the fact that we're not efficient at galloping means it would be a tougher workout than running. Maybe athletes should start mixing some alternative gaits into their usual exercise routines. Who knows—with practice, you might become the best galloper in the whole world.

Fiers P, De Clercq D, Segers V, & Aerts P (2012). Biomechanics of human bipedal gallop: asymmetry dictates leg functions. The Journal of experimental biology PMID: 23239890

Image: Devon D'Ewart (Flickr)

12 Days of Inkfish, Day 12: Cuddlefish

Sometimes a cuttlefish wants to cuddle, and sometimes it wants to attack you with its face and ingest you whole. Both sides of the cephalopod's personality are on display in this video from the BBC. Also on display: the giant cuttlefish's unbelievable full-body strobe light effect. This is an animal you want to stay on the good side of.

Thanks for celebrating the 12 Days of Inkfish with me! Next week, regularly scheduled programming will return. Stay tuned for new science and new marveling at nature's old—but spectacular—tricks.

Until then, did you miss any of these?

Day 1: What happens when inkfish receive gifts
Day 2: Life as an upside-down jelly
Day 3: Head explosions and a reverse sun
Day 4: The help desk answers "orangutan stop following me" and other reader questions
Day 5: A video of grebes running on water to prove their commitment
Day 6: How Zion Canyon is like the Princess and the Pea
Day 7: Which posts won Best Mustache and other superlatives in the 2012 yearbook
Day 8: This nebula is a square peg in a round universe, thank goodness
Day 9: These airport worms are hard at work eating your garbage
Day 10: Sending you all on an acoustic scavenger hunt (please report back!)
Day 11: The most charming breeds of purse animals

Image: Screenshot from "Animal mating rituals of giant cuttle fish in the blue Australian ocean waters" by BBC Worldwide

12 Days of Inkfish, Day 11: Purse Animals






Images copyright Patrick Gries 2010, via Facebook.

12 Days of Inkfish, Day 10: Acoustic Scavenger Hunt





Image: Sound Around You

12 Days of Inkfish, Day 9: Airport Worms

While you were vacationing on New Year's Day, nearly two million worms were working hard at Charlotte Douglas International Airport. The airport installed them in the fall of 2012 as part of its new recycling center. By munching through passengers' coffee grounds, used paper towels, and uneaten French fries, the worms are making garden fertilizer out of what used to be landfill fodder.

At the recycling center, employees first sort through the airport's 25 daily tons of trash. Recyclables such as cardboard, aluminum, and plastic are sold. (One airline, project director Bob Lucas said in November, discards entire sleeves of plastic cups even if only a few were used during a flight.) Clothing, which Lucas said panicked passengers dump in the trash when their bags are overweight, is collected by a "group of ladies" who clean and donate it.

As for the worm food itself, it gets heated and pre-composted before finally going to the red wigglers. The airport plans to use waste from the worms to fertilize its grounds. The slimy new employees are happy and—now that Lucas has figured out how to stop them fleeing during a thunderstorm—seem to plan on staying at their jobs.

Image: Sparrows' Friend (via Flickr). Thanks to Leigh for the tip!

12 Days of Inkfish, Day 8: Square Peg in a Round Universe

We can all agree there's too much round stuff in space, right? All those planets and stars and orbital paths and moon craters and disks of debris get old. The most variation you can usually hope for is an astroid shaped like a potato.

Here, for some relief, is the aptly named Red Square nebula. Researchers Peter Tuthill of Sydney University and James Lloyd of Cornell University created this image of the cloud, which surrounds a star called MWC 922.

The researchers think its square shape might be due to a lucky viewing angle on our part. The nebula may really be two cones of gas pointing outward, as if the star at the center were a cheerleader holding a giant megaphone in either hand. From our angle, the nebula looks like a giant X or square. If it turned 90 degrees, we'd find ourselves facing—yet again—some round stuff in space.

Image: Peter Tuthill, Sydney University Physics Dept., Palomar and W.M. Keck observatories (via APOD)