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Like the clever and many-armed cephalopod, Inkfish reaches into all areas of science and brings you interpretations of the newest stories.
Without plagues, earthquakes, and unhinged criminal masterminds, the residents of Gotham might never need to put up the bat signal. Real bats, of course, are less concerned with responding to emergencies than with eating bugs. But like Batman, they do just fine—if not better than ever—in recently devastated environments. Specifically, forests that have burned down.
For five weeks in the summer of 2002, a wildfire tore through national forests in the Sierra Nevada mountains. The McNally Fire was started by a careless human, and ended with over 150,000 acres burned. A year later, scientists came by to see how the bats were doing.
"Bat ecologists have known for a while now that bats respond favorably to controlled, low intensity fires," says Michael Buchalski of Western Michigan University, one of the study's authors. "We were more interested in the effects of large, natural fires." These blazes can completely destroy the forest canopy, leaving an area unrecognizable.
Researchers visited 14 sites in the woods, half in burned areas and half in areas that were untouched. They left devices that recorded the ultrasonic cries of echolocating bats at night. Since tallying up all the bat activity they heard could be misleading—one flourishing species of bats might mask the disappearance of another—they divided the recordings into groups of similar-sounding calls, representing groups of bat species.
The researchers estimated how plentiful each type of bat was based on how often they heard its calls. Comparing burned and unburned areas, they found that no bat group was bothered by the fire. Instead, every group of bats was at least as plentiful in the fire-scorched areas—and some were doing even better than usual.
Despite the absence of costumed criminals, a few factors might account for bats' increased activity in a scorched landscape. Bats hunt by swooping through the air and searching for insects below. With much of the vegetation cleared out by fire, insects have fewer places to hide, and hunting bats have a clearer view for their echolocation.
Additionally, the first plant regrowth after a fire leads to a boom in insect species. This means there's more prey than ever available for hungry bats. "One-stop shopping!" says coauthor Joseph Fontaine of Murdoch University. Those bats may find new places to roost—or, if you prefer, build their secret lairs—inside dead trees.
Buchalski and Fontaine say bats probably need a mix of landscapes to thrive, including areas that have recently burned. Carefully allowing forests to burn more like they did in the past could lead to "healthier forests and healthier wildlife populations," Buchalski says. "However, this is a very contentious issue within the field of forestry management."
"We have spent the majority of the last century suppressing and excluding fire," Fontaine adds. "More fire right now is probably not a bad thing whatsoever." (For non-human animals, anyway.) With climate change increasing the potential for drought and wildfire, the authors say that understanding how different species deal with fire is becoming more important.
Bats aren't the only animals that appreciate a fire. Fontaine says deer mice and other short-lived rodents respond very well to fire, and deer and elk like to chew on the soft new shrubs that have regrown a few years later. Several types of woodpeckers, he adds, rely on fires. The California spotted owl doesn't mind fire—like a bat, it hunts from above and doesn't need a live tree for its nest.
Although forest fires are a boon for many species, the robin doesn't seem to be among them.
Buchalski, M., Fontaine, J., Heady, P., Hayes, J., & Frick, W. (2013). Bat Response to Differing Fire Severity in Mixed-Conifer Forest California, USA PLoS ONE, 8 (3) DOI: 10.1371/journal.pone.0057884
Image from public domain files at Wikia.
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Buchalski, M., Fontaine, J., Heady, P., Hayes, J., & Frick, W. (2013) Bat Response to Differing Fire Severity in Mixed-Conifer Forest California, USA. PLoS ONE, 8(3). DOI: 10.1371/journal.pone.0057884
There's more to a pair of rat noses than meets the eye. Like tiny, leashless dogs, rats like to sniff each other all over when they meet. Yet not all of this sniffing is aimed at gathering scents. Some of it seems to transmit messages such as "I'm in charge" or "Be cool" or "Please don't bite my face."
Rats and other animals give off odors from the "face, flanks, and anogenital region," says neuroscientist Daniel Wesson of Case Western Reserve University. So it's not surprising that these regions are where rats aim their sniffers when they cross paths. To find out whether there might be more going on, though, Wesson outfitted rats with head-mounted devices that measured the speed of their sniffs. Then, after recording videos of these rats encountering each other, he looked at how sniff frequency lined up with different stages of the rodents' interaction.
He saw that all rats sped up their sniffing when their noses were pointed at each other's flanks or rear ends. But when the rats were sniffing each other's faces, their behavior depended on whether they were socially dominant or subordinate. Higher-ranking rats sped up their sniffing as usual. Lower-ranking rats slowed down their own sniffing in response.
This seemed to be an "appeasement signal," akin to climbing into one's own locker when the school bully approaches. Wesson found that when subordinate rats didn't give this signal—when they kept up their sniffing at the usual rate—dominant rats were quicker to pick a fight.
To further test this idea, Wesson treated the insides of the rats' noses with zinc sulfate, making them temporarily lose their sense of smell. Even though they weren't gathering any odors, rats kept on sniffing. And when they were face-to-face, they acted the same as always: dominant rats sniffed faster, while subordinate ones slowed down to avoid trouble. "This sniffing behavior was interestingly resilient," Wesson says.
Sniffing seems to be a form of communication for rats—but only sniffing in the face, not other body parts. Wesson says this may be because face sniffing is an especially vulnerable position for a rat or other animal to be in. When their eyeballs and whiskers and biting parts are all in close proximity, maybe it's a good time for rats to make clear that they don't want a fight.
Alternately, face-to-face might be the only way a rat can detect another rat's sniffing; maybe the signal wouldn't get through if it were aimed at the tail end. "These are different theories we are testing now," Wesson says. There may also be ultrasonic squeaks or other signals invisible to humans that contribute to the conversation between two rats.
If rats use sniffing for communication, and not only for gathering smells, do other social sniffers do the same thing? "I would predict so," Wesson says. "Other rodents likely use this behavior, as could possibly cats and dogs." He points out that neighborhood dogs who meet on a walk will sniff each other, then either part peacefully or start fighting. Some signal in their sniffing behavior may make the difference, though this idea would have to be tested.
That's not to say dogs or rats aren't also gathering actual smells when they sniff. It would be "frankly silly" to discount the importance of smell in an animal's life, Wesson says. It seems there's much more going on, though, when an animal sticks its nose into the world.
Wesson, D. (2013). Sniffing Behavior Communicates Social Hierarchy Current Biology DOI: 10.1016/j.cub.2013.02.012
Image: Daniel Wesson.
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Humans and our lice are even closer travel companions than Kourtney and Kim when they took New York. The parasites cling to us more tightly than Paris Hilton's new BFF. They've been such cozy acquaintances of ours, in fact, that the story of human evolution is written into their genes.
That's what Marina Ascunce and other researchers at the University of Florida found when they sampled lice from around the world and compared their DNA. In the chromosomes of these wingless bloodsuckers, they discovered a window on human culture almost as good as a flip through the TV guide.
"Lice" is a four-letter word that can inspire dread in the hearts of kindergarten teachers, moms and dads, and well-coiffed middle schoolers. An infestation of head lice is usually harmless, if horrifying. Ascunce and her coworkers point out, though, that head lice in the United States, Nepal and Ethiopia have been found carrying disease-causing bacteria.
What Not to Wear
More dangerous than head lice are body or clothing lice, which mostly affect the homeless and people living in refugee camps. These lice can carry at least three kinds of bacteria that are dangerous to humans. Over the past few decades, the authors write, there have been several disease outbreaks tied to body lice—including an outbreak of epidemic typhus (caused by the bacterium Rickettsia prowazekii) in Burundi that sickened more than 45,000 people.
Body and head lice belong to the same species (Pediculus humanus). Yet the two subspecies, like knockoff shows on different TV channels, make up separate populations that don't encounter each other in nature.
The Pickup Artist
The researchers used lice that had been plucked off of humans in 11 locations around the world. Head lice came from a few sites each in the United States, Asia, and Europe, plus Honduras. There were also body lice from Nepal and from a homeless shelter in Canada, for a total of 93 lice.
Incidentally, head lice infestations usually include more females than males. It's not clear why, but when you have lice, your scalp is like one big rose ceremony.
House Hunters International
By letting them stow away in our hair while our own species migrated around the world, we've created unique geographic populations of lice. The head lice in this study fell into into three distinct groups based on their shared DNA. Asian lice (from Thailand, Nepal and Cambodia) made up one group. Lice from Honduras were another distinct group. Lice in the United States, though, were in the same genetic cluster as those from Europe.
Louse DNA shows plenty of evidence of inbreeding. This isn't too surprising when you consider that populations reproduce as fast as they can while staying marooned on one person's head (and that new infestations can result from just one egg-bearing female crawling onto a fresh scalp). The most-inbred lice were found in New York.
19 Kids and Counting
Compared to their highly inbred head cousins, body lice showed a little more diversity. One reason for this, the authors point out, may be that body lice have more young. A female head louse can leave 150 eggs nestled and glued into her host's hair; a female body louse may leave twice that many eggs in the seams and hems of a person's clothing.
MXC: Most Extreme Elimination Challenge
Another factor that has probably contributed to low diversity in lice populations is our ongoing effort to kill them. Head lice infestations have increased around the world, the authors write, in part because the bugs have developed resistance to the insecticides we dump on kids' heads. A dousing with poison may leave behind a few hardy lice, which can then repopulate the whole area. (Biologists call this kind of population narrowing and regrowth a "bottleneck.")
Britain's Worst Celebrity Driver
Actually it has nothing to do with lice, but did you guys know this was a real show?
The Real World: Boston
The American lice sampled by Ascunce and her colleagues (from New York, San Francisco, and Florida) were a genetic match to the European lice (which came from Norway and the United Kingdom). If this pattern holds up across the United States and Europe, it would suggest that the lice Americans carry traveled to the New World along with European colonists. In other words, we have Columbus's lice.
Sarah Palin's Alaska
The genetically distinct lice found in Honduras, though, don't seem to have come over with the pilgrims. The authors think it's possible that the Honduran bugs represent the native American lice. Perhaps they came here on the heads of more ancient humans who crossed into this continent from Asia, traveling across the Bering Strait and down through Alaska long before Europeans arrived.
An earlier study of louse mitochondrial DNA (genetic material that's only passed through mothers) turned up a distinct genetic group that's present in Europe, Australia, and the New World, but not in Africa. It's possible that this DNA, rather than having come from the lice our most ancient ancestors carried out of Africa, represents lice those humans picked up while hobnobbing with Neanderthals on their way through Eurasia.
Survivor: Heroes vs. Villains
The story of our conflict with lice is a classic one. As long as the insects keep developing resistance to our poisons and fighting back when we try to kill them, this series isn't likely to ever get canceled.
Ascunce, M., Toups, M., Kassu, G., Fane, J., Scholl, K., & Reed, D. (2013). Nuclear Genetic Diversity in Human Lice (Pediculus humanus) Reveals Continental Differences and High Inbreeding among Worldwide Populations PLoS ONE, 8 (2) DOI: 10.1371/journal.pone.0057619
Image: Gilles San Martin (via Wikimedia Commons)
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Ascunce, M., Toups, M., Kassu, G., Fane, J., Scholl, K., & Reed, D. (2013) Nuclear Genetic Diversity in Human Lice (Pediculus humanus) Reveals Continental Differences and High Inbreeding among Worldwide Populations. PLoS ONE, 8(2). DOI: 10.1371/journal.pone.0057619
The business end of a cuttlefish is no place a small crustacean wants to be. Cuttlefish are hunters who creep around in camouflage—virtually indistinguishable from a gray patch of gravel or a branching green seaweed—then lash out with their tentacles, turning a passing shrimp into shrimp toast. Oh, and they're colorblind. Despite this apparent handicap, though, learning to hunt doesn't take a lifetime. Baby cuttlefish figure it out almost as soon as they hatch.
"Newly hatched cuttlefish are mini adults," says Anne-Sophie Darmaillacq of the Université de Caen Basse-Normandie in France. They behave similarly to full-grown cuttlefish, that is, and look like toy versions of their parents. Yet those grownups are long gone. "Parents die after the spawning season," Darmaillacq says. Since cuttlefish are born as orphans, they have to be able to look after themselves right away.
For this reason, Darmaillacq and her coauthors wondered how the eyesight of junior cephalopods compares to that of their adult relatives. To find out how quickly a just-hatched cuttlefish's eyes get up to speed, they collected eggs of the cuttlefish Sepia officinalis off the coast of France. (The genus name describes a cuttlefish's brown ink, not its many-colored body.)
Zero to 30 days after hatching in the lab, the tots were tested in a carousel-like device. While a cuttlefish sat stationary at the center, a cylindrical screen with vertical stripes rotated around it at various speeds. Animals that were able to distinguish the stripes spinning by would follow them with their eyes, or by rotating their whole bodies. One set of test screens had black, white and gray stripes. Another had stripes that produced different polarizations of light.
Human eyeballs don't distinguish light polarization, which is when light waves all wiggle in the same orientation as they travel, as after passing through a filter. Bees and some other animals can see this polarization and use it to navigate. Cuttlefish, too, can see light polarization, and scientists are familiar with the architecture in a cuttlefish's retina that allows this. But Darmaillacq says the ability hadn't been studied as much in young cuttlefish.
The tests in the striped carousel showed that cuttlefish who had just hatched were already great at tracking black, white and gray stripes, and got even better over their first 30 days of life. They also started life with some skill at seeing stripes of light polarization, and improved as they aged.
Watching stripes spin is less important than knowing when to pounce on a passing meal, though. In a second set of experiments, the researchers showed young cuttlefish two types of prey trapped inside glass tubes and waited to see which the cuttlefish would attack. One prey was mysid shrimp, which hide by being transparent—but they're much easier to spot if you can see light polarization. The other prey was crabs, which both cuttlefish and humans can see without the help of polarized light.
In a regular glass tube, cuttlefish eagerly attacked all the prey. But in a tube covered with a plastic film that hid light polarization, cuttlefish were more reluctant to attack the shrimp. As they grew older, they got faster at spotting all their victims, but they still didn't like to attack transparent prey unless they could see the polarized light coming off their bodies.
Darmaillacq says newly hatched cuttlefish seem to already have the cognitive skills that make a good hunter, such as learning, attention, and decision making. Her experiments also show that cuttlefish can see light polarization soon after hatching, and that skill helps them find transparent prey and decide when to pounce.
The cuttlefish's colorblindness is a deficit that's almost impossible to believe once you've watched this camouflage master in action. Darmaillacq says the ability to see light polarization may make up for the cuttlefish's missing color vision.
Polarized light helps young cuttlefish spot some of their favorite transparent snacks, which would otherwise be hidden. Additionally, "Wavelengths vary a lot depending on the depth [of the water]," Darmaillacq says. "Light polarization does not." In other words, colors can lie in the ocean, but polarization tells the truth. This means cuttlefish can see well enough that their prey—like the fish in this video from the New England Aquarium—never see them coming.
Cartron, L., Dickel, L., Shashar, N., & Darmaillacq, A. (2013). Maturation of polarization and luminance contrast sensitivities in cuttlefish (Sepia officinalis) Journal of Experimental Biology DOI: 10.1242/jeb.080390
Image: Leonard Clifford (Flickr)
Video: New England Aquarium
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Cartron, L., Dickel, L., Shashar, N., & Darmaillacq, A. (2013) Maturation of polarization and luminance contrast sensitivities in cuttlefish (Sepia officinalis). Journal of Experimental Biology. DOI: 10.1242/jeb.080390
Don't trust your kids. Like a miniature, juice-fueled army with subliminal messaging tactics, they can get inside your mind and make you do things. You won't realize what's happening until you step out of your low-flow shower one morning, turn the calendar page, and see a smug endangered trout looking back at you.
Though we usually think of education flowing down from parents and teachers to children, some people would prefer it to go upstream too. Environmental educators, for example, may hope when they teach groups of children about recycling or saving energy that they'll go home and impose new habits on their parents.
In the Seychelles, an archipelago nation in the Indian Ocean, preserving the wetlands is a major concern. An NGO called Wildlife Clubs Seychelles runs extracurricular "wildlife clubs" in the schools; these groups organize projects and go on field trips to learn about the environment. Researchers from Imperial College London took advantage of the widespread clubs to find out whether environmental education can travel against the current.
During the year before the study, certain wildlife clubs had taught a unit on wetlands while others studied something else. Lead author Peter Damerell and his colleagues studied 7 wildlife clubs that had done the wetlands unit and 8 that hadn't, with kids in the groups ranging from age 7 to 15.
The researchers distributed a questionnaire for kids to fill out in school. A second set of questionnaires went home to the kids' parents. The forms included questions to test wetland knowledge as well as questions about how people used water in their homes.
When the questionnaires came back, there were 137 complete parent-child pairs in the batch. Kids who had participated in a wetland unit scored better on questions about wetland knowledge (what kinds of species live in local wetlands, what threatens these habitats, and so on). More surprisingly, the authors report in Environmental Research Letters, the kids' knowledge had rubbed off on their parents. Moms and dads of wetland-educated kids outscored parents of kids who hadn't studied wetlands.
The questionnaires also asked parents point-blank whether they'd learned anything about wetlands from their children. Their answers, it turned out, were totally unrelated to their actual scores. Even when kids had taught their parents something, parents didn't necessarily know it.
On questions about people's water use in their homes—whether they made choices that use less water, in light of water shortages in the Seychelles—families whose children had studied wetlands with their wildlife clubs again scored significantly better. (It's also possible, the researchers note, that these families just knew the "right" answers to water-use questions. It would take more research to find out whether they actually used less water.)
Since scores didn't increase with children's ages, Damerell and his coauthors don't think regular classroom time did the trick. The wildlife clubs' field trips and outdoor projects may have been just exciting enough to make a real impression on kids—and to get them talking about their fun swamp adventures with their parents. Er, indoctrinating them.
Damerell, P., Howe, C., & Milner-Gulland, E. (2013). Child-orientated environmental education influences adult knowledge and household behaviour Environmental Research Letters, 8 (1) DOI: 10.1088/1748-9326/8/1/015016
Image: jmb_craftypickle (Flickr)
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Damerell, P., Howe, C., & Milner-Gulland, E. (2013) Child-orientated environmental education influences adult knowledge and household behaviour. Environmental Research Letters, 8(1), 15016. DOI: 10.1088/1748-9326/8/1/015016
Anyone who's walked a dog and seen it spring to attention when another dogs rounds a corner—even though that animal is still a full block away—may have wondered how exactly dogs recognize each other. What makes a golden retriever perk up its ears and wag its tail at an approaching greyhound but not, say, a stroller? Why does it ever occur to a dachshund to play with a pit bull in the park? Why don't average-sized dogs chase toy breeds away as if they were squirrels?
You might assume dogs, with their powerful noses, are getting an advantage from scent. Perhaps dog breeds all smell the same, despite looking wildly different. A new study, though, shows that dogs can find each other by sight alone. Dogs are able to spot another dog, no matter the breed, from among a crowd of other animals. Scientists don't know how they do it.
Since other animals such as sheep, macaques, and cows have shown in the lab that they can recognize their peers by sight, scientists in France asked whether dogs could do this when challenged with a full complement of breeds. To understand the magnitude of the problem a dog faces, consider that there are 400 to 500 registered dog breeds. Dogs are more diverse than any other animal species on Earth. Furthermore, their vision isn't that great. If Fido wants to find a mate, though, he'd better know the difference between a Pomeranian and a fluffy cat.
Bertrand Deputte of the National Veterinary School at Alfort, France, and his coauthors recruited nine dogs for their study. All the dogs were pets owned by veterinary students. They were a mix of male and female, and mostly mixed-breeds.
In each stage of the experiment, a dog sat facing two screens on tables while a human stood behind it. (The human experimenter, to make absolutely sure he didn't give any hints, stood motionless and wore dark glasses.) On the experimenter's command, the dog walked forward and chose one of the two screens by placing its paw on a table.
Choosing the correct picture got the dog a food reward. But what was "correct" shifted over the course of the experiment, as the researchers took the dogs through a series of challenges.
In early sessions, dogs won a treat if they chose a screen showing a dog's face over an empty screen. They they had to choose a dog's face over a cow's face, where the dog and cow were the same every time but kept swapping screens. Then the dogs had to generalize: the screens showed dog and cow faces the subjects hadn't seen before, and they had to choose the dog.
At last came the main challenge: dogs versus everything else. One screen showed a dog's face (a different dog every time) and the other showed some non-dog species (cow, cat, rabbit, human, bird, and so on). Every picture was zoomed in on the animal's head, so that the canine subjects couldn't get any clues from body size or shape—not to mention movement, sound, or smell. Some faces were shown straight on; others were in profile or three-quarters view. Nevertheless, every dog in the experiment succeeded.
"We were rather surprised by the ease dogs had," Deputte says, "in spite of huge variability of dog breeds and the variety of animal and humans faces that constituted the other category." All nine dogs, once they'd learned what the human experimenter wanted, could consistently pick out the dog faces on the screens.
To prove the dogs really knew their stuff, researchers also reversed the task and had dogs pick out the picture that wasn't a dog. They aced this test too.
"We couldn't tell how the dogs succeeded" at grouping dog faces from various breeds and different angles all into one category, Deputte says. He believes his results show that dogs have a "concept of dog." Somehow, our pets know immediately whether the animal walking toward them is dog or not-dog. Along with knowing when to sniff the approaching animal's rear end, this may be a power we hopeless humans will never understand.
Autier-Dérian D, Deputte BL, Chalvet-Monfray K, Coulon M, & Mounier L (2013). Visual discrimination of species in dogs (Canis familiaris). Animal cognition PMID: 23404258
Images: George Thomas (Flickr); Dominique Autier-Dérian/Animal Cognition
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Autier-Dérian D, Deputte BL, Chalvet-Monfray K, Coulon M, & Mounier L. (2013) Visual discrimination of species in dogs (Canis familiaris). Animal cognition. PMID: 23404258
Finding just the right gift for a significant other sometimes means relying on hints; this is especially true if you are a bird and your significant other is also a bird. Even the cleverest corvids aren't great with wish lists. Male Eurasian jays, though, seem to be able to deduce which treats their mates want most.
Sharing food is an important courtship ritual for the Eurasian jay (Garrulus glandarius). Passing snacks to each other helps the birds form, and nourish, long-term relationships. A female might accept any tidbit her partner gives her, whether she wants it or not, for the sake of boosting the bond—or just because she plans on stashing it for later. If a male can correctly guess what foods his mate prefers, though, he could increase his value in her beady eyes.
Figuring out what's in another animal's mind is no mean feat. Yet Eurasian jays are a member of the famously bright corvid family; relatives have been known to reenact Aesop's fables, outsmart small children, and sled down snow-covered roofs. Nicola Clayton and other researchers at the University of Cambridge looked for evidence that these birds are also capable of seeing from another's perspective.
The experiment relied on "specific satiety," which is when an animal gets tired of one kind of food but still has an appetite for a different food. This phenomenon is familiar to anyone who pushes away a plate of pasta, feeling stuffed, and then considers a dessert menu.
For the seven pairs of Eurasian jays in the study, the foods in question weren't pasta and tiramisu but worms and more worms. Specifically, wax moth larvae and mealworm larvae. When they were first fed on one kind of larva and then offered a choice between two bowls, both male and female birds preferred to eat the kind of larva they hadn't already had.
To see whether male jays understood that females felt this way too, the researchers fed female jays either wax moth or mealworm larvae while their male partners watched from the other side of a screen. Then they offered the male both kinds of larva, and let him choose which ones to pick up and pass to his mate through the screen.
After watching their mates eat one kind of larva, male jays were more likely to feed them the other kind, Clayton reports in PNAS. It wasn't because the males themselves were hungry for that kind of food; the researchers checked this in a separate experiment by offering the males their own bowls of larvae after watching females feed. Having already eaten meals of "soaked dog biscuits, cheese, seeds, nuts and fruit," the males had their own preferences about wax moths versus mealworms (two flavors you won't find in a Whitman's sampler). But when feeding their mate, they followed her preference instead.
Nor were the females telling their mates what they wanted, in some secret bird language, right there at the screen. The researchers know this because when males couldn't see the first feeding, they failed to give their mates their preferred larvae. The males had to see females being fed to guess what they'd want later.
The study used a small number of birds in unnatural circumstances. If Eurasian jays can truly put themselves in each other's shoes, though, they are members of the cognitive elite. Deducing another's intentions or desires is something we humans rarely admit other animals are capable of. But then, it can be hard to take a hint.
Ostojic, L., Shaw, R., Cheke, L., & Clayton, N. (2013). Evidence suggesting that desire-state attribution may govern food sharing in Eurasian jays Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1209926110
Image: Eurasian Jay mating pair engaged in food-sharing, by Ljerka Ostojic.
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Ostojic, L., Shaw, R., Cheke, L., & Clayton, N. (2013) Evidence suggesting that desire-state attribution may govern food sharing in Eurasian jays. Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.1209926110
Getting older is not a recipe for crotchetiness. Although those two cranky Muppets will always be up in their balcony, Americans in general don't become less happy with age. If anything, they get happier.
The trajectory of people's happiness over a lifetime is tricky to study, because in a given year you're capturing not only your subject's age but also the current events. You need to follow a large group of people over many years, and you need them to be all different ages when the study starts.
Angelina Sutin and her colleagues at the National Institute of Aging in Maryland had just such a dataset to work with. Called the Baltimore Longitudinal Study of Aging (BLSA), this project has been running for more than five decades and has gathered data on people born everywhere between 1885 and 1980. These subjects have answered questions about their happiness on many occasions—some as many as 19 times—throughout their lives.
Want to find your own happiness score? Answer the following questions on a scale from 0 to 3, where 0 is "rarely or never" and 3 is "most or all of the time." In the past week of your life, how frequent were these feelings?
I enjoyed life
I felt I was just as good as other people
I felt hopeful about the future
I was happy
Summing the four numbers will give you your well-being score. If you were in the BLSA, that score would be your data point for today.
When the researchers put all 2,267 subjects together and looked at how their happiness changed with age, they got a decidedly downward slope. A frowny face, if you will.
age = : (
It looked like aging made people less happy. But then the researchers tried a different tactic. Instead of lumping all their subjects together, they grouped them by when they were born. That frown turned upside down:
age = : \
Within each birth year, the results now looked like a somewhat more optimistic "meh?" face. Every group's well-being slightly (but significantly) improved with age.
The first set of results had sloped downward because people who were born earlier reached lower endpoints of well-being. In the graph, you can see that someone born in 1905 or 1925 is likely to reach a 9 or a 10 later in life; someone born in the 1960s might make it nearly to 12 (a perfect score).
Sutin thinks this could have to do with the biggest national frowny-face of all: the Great Depression. People who lived through this time, she writes, may have felt lasting psychological effects. Although their well-being still improved as they aged, the cloud of the Depression may have lingered.
(Sutin notes also that younger and older adults, according to previous studies, treat this set of well-being questions and the 0-to-3 scale similarly. This suggests the results aren't just happiness inflation—say, younger people reporting a 12 for the same feelings that older people would rate a 10.)
Aside from increasing economic prosperity in the United States, there are plenty of other reasons people may have felt happier in more recent decades. Sutin cites increased life expectancy, decreased infant mortality, better nutrition, less disease, and more women in the workplace as possible factors. The twentieth century also saw faster travel, the invention of the Internet, and the eradication in America of both the polio virus and gelatin-based entrées. There's a lot to be happy about.
Now that Sutin has found that the average American seems to have an upward trajectory of well-being, she's interested in people's individual paths: what makes one person's happiness increase more or less (or decrease) over time?
In this study, subjects who were white had higher well-being scores on average, as did those with more education. Sutin hopes to pick apart the social, economic, and health factors that affect how happiness changes with age. When everyone can feel as :) as they want, we'll really be living in the future.
Sutin, A., Terracciano, A., Milaneschi, Y., An, Y., Ferrucci, L., & Zonderman, A. (2013). The Effect of Birth Cohort on Well-Being: The Legacy of Economic Hard Times Psychological Science DOI: 10.1177/0956797612459658
Image: a 102-year-old woman, by Uppy Chatterjee (Flickr)
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Sutin, A., Terracciano, A., Milaneschi, Y., An, Y., Ferrucci, L., & Zonderman, A. (2013) The Effect of Birth Cohort on Well-Being: The Legacy of Economic Hard Times. Psychological Science. DOI: 10.1177/0956797612459658
Pea aphids are even better at "stop, drop and roll" than elementary-schoolers. When a threatening ladybug or grazing deer approaches the stem where an aphid is sucking sap, it lets go and plummets toward the ground. By holding its limbs in just the right way, though, the insect can tumble into an upright position before sticking the landing.
The ground is a dangerous place for a small wingless animal, so it might help a falling pea aphid (Acyrthosiphon pisum) to hit it running. Or, better yet, to land feet-first on a lower leaf and never reach the ground at all. A group of scientists in Israel subjected pea aphids to predator scares, bouncing falls, and amputations to investigate their cat-like maneuvering.
In one experiment, the researchers placed a ladybug onto a fava bean plant where aphids were feeding. They covered the ground below with petroleum jelly so the insects would be caught however they landed.
As the ladybug crawled up the plant, alarmed aphids dropped to the ground. Falling from 20 centimeters, nearly every aphid landed right side up—"like a defenestrated cat," the authors note cheerfully.
If a live aphid is like a cat, a dead one is closer to buttered toast. The team used tweezers to drop upside-down aphids from 35 centimeters up. Some aphids started out alive and well; others were dead. The third (and least fortunate) group of aphids were still alive but had their limbs and antennae removed with a razor blade. Among the living, limbed aphids, 95 percent landed upright. Only about half of the dead aphids did, though. The number was even lower for the limbless group, reduced to flipping through the air like sesame seeds.
High-speed photography and mathematical modeling revealed the secret of the pea aphid. After letting go of a plant, it stretches its antennae forward and reaches its hind legs back and up. Then it freezes.
This position, the researchers discovered, it only aerodynamically stable when right side up. Holding its appendages stiffly in position like a skydiver, the falling insect will tumble until it's belly-down. Then it stays that way until it lands, the authors report in Current Biology.
"I was surprised and impressed by the simplicity of the righting mechanism," says Gal Ribak, a biologist at the Israel Institute of Technology and one of the lead authors. To land upright, the aphids only need to assume the right pose and stay that way. "All the rest is taken care of with the help of air resistance and gravity."
To see whether falling upright helped aphids land on a safe leaf, instead of going all the way to the groung, the researchers dropped insects directly over leaves. Those that were feet-first when they hit a leaf were able to stick the landing about half the time. When turned the wrong way, though, the aphids were guaranteed to bounce off the leaf and into danger.
The real danger in the lab, of course, came not from predators on the ground but from the scientists, who now snipped the ends off the aphids' legs to see if sticky pads there were helping them land. Once their wounds stopped oozing, the insects took another trip through the air. This time only 1 out of 20 caught the leaf.
Ribak studies animal locomotion within the university's department of aerospace engineering. That's because pea aphids, with their aerodynamical tricks, may have something to contribute to aircraft design. The species is also known for apparently capturing energy directly from the sun, something that's usually impossible if you're not a plant. Technologically, when it comes to these falling insects, we may never catch up.
Ribak, G., Gish, M., Weihs, D., & Inbar, M. (2013). Adaptive aerial righting during the escape dropping of wingless pea aphids Current Biology, 23 (3) DOI: 10.1016/j.cub.2012.12.010
Image: Ribak et al. (see the whole video here!)
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Ribak, G., Gish, M., Weihs, D., & Inbar, M. (2013) Adaptive aerial righting during the escape dropping of wingless pea aphids. Current Biology, 23(3). DOI: 10.1016/j.cub.2012.12.010
This post originally appeared in August 2012. Inkfish will return to its regularly scheduled wacky animals next week.
The office of postmaster general to the United States used to come with a perk totally unrelated to mail. In the unlikely event that an accident wiped out the president, vice president, and every member of their cabinet, the postmaster general would become the leader of the country.
In reality, the line of succession has never gotten beyond the vice president. But there are 16 people lined up behind the VP to take over (a list that no longer includes the postmaster general and now culminates, less quaintly, with the secretary of homeland security). In the United Kingdom, the order of succession to the throne winds bafflingly through a giant family tree of princes, dukes, viscounts, and so on.
Wasps of the species Ropalidia marginata never have to argue about titles or families: when the queen dies or disappears, the other wasps in the colony unanimously agree on who her successor is. And if that queen disappears too, they know who comes after her. Though the ordering system is invisible to human eyes, the wasps adhere strictly to their line of succession and follow it all the way down (if necessary) to their equivalent of the postmaster general.
Alok Bang and Raghavendra Gadagkar, researchers at the Indian Institute of Science in Bangalore, have been determinedly assassinating wasp queens to try to figure out how the R. marginata system works. Until the researchers get to her, each nest's queen lives a peaceful life. She doesn't bother anyone, and no one bothers her as she pumps out new generations of fertilized eggs.
The queen's quiet lifestyle, like that of most royalty, is in stark contrast to the lifestyle of her subjects. All around their docile ruler, worker wasps live in continuous violence. Gadagkar says the wasps chase, bite, and "nibble" one another, pin each other in place by holding body parts in their mouths, and crash down on each other from above. These displays of aggression don't usually injure the wasps, but maintain a hierarchy of dominance among them.
When the peaceful queen dies, or is plucked from the nest by interfering scientists, things get shaken up. One worker wasp—and only one—suddenly becomes hyperaggressive. Within minutes of the queen disappearing, this worker begins attacking the wasps around her at 10 or even 100 times her usual frequency, Gadagkar says. She distributes her attacks evenly among anyone nearby, and no one fights back. It's all a show to announce that this wasp is the heir to the throne.
Over the following week or so, the heir's aggression dies down and her ovaries develop. She becomes another peace-loving, egg-laying machine.
The researchers believe that this successor is chosen somehow before the original queen disappears. Even though she's outwardly identical to the other wasps in the nest, she's predestined to be second in line to the throne. "The fact that there is invariably one and only one individual who becomes hyperaggressive" is one clue, Gadagkar says. That no one challenges this hyperaggressive individual is an even stronger clue. And in previous studies, the researchers have shown that the heir isn't simply the first wasp to get the news of the queen's death. The successor seems to know who she is ahead of time, and the other wasps know and respect it too.
If that weren't impressive enough, Bang and Gadagkar have now found that when they remove the first heir, a second one steps up just as quickly. In a new paper in PNAS, the authors say they've discovered a succession of at least five potential queens.
Each of these new queens jumps into action as soon as a the previous queen disappears, attacking any workers around her. Again, only one wasp steps forward, and no one challenges her. Within several days, this new queen starts laying her own eggs and maintaining the colony. In an entire nest of 20 or 30 individuals, the researchers say, there's no reason to believe the succession doesn't continue—maybe down to the very last wasp.
Having an agreed-upon order of succession makes sense for insects living in small colonies like R. marginata, the authors say. Unlike in a large honeybee colony, where queens are determined from birth and workers know they'll never lay their own eggs, workers in the termite colony actually have a shot at reproducing. Knowing where they are in the queen queue could help them decide whether to stay in their original nest or move out to start a nest of their own.
Even if it makes perfect sense for the wasps to have an orderly system of succession in place, that doesn't explain how on Earth they figure it out.
"That is the million-dollar question we are working on!" Gadagkar says. The researchers found that older wasps were more likely to be the immediate heirs to the throne, but the order doesn't go strictly by age. It also doesn't have anything to do with the dominance hierarchy in the nest.
"Perhaps it is something very subtle, related to the internal physiology of the wasp, that the wasps themselves can detect and which we have not yet discovered," Gadagkar says. Like obscure duchesses and earls, the wasps know their place in line—indecipherable as it may be to the rest of us—and wait for their day to step forward.
Alok Bang, & Raghavendra Gadagkar (2012). Reproductive queue without overt conflict in the primitively eusocial wasp Ropalidia marginata PNAS : ... Read more »
Alok Bang, & Raghavendra Gadagkar. (2012) Reproductive queue without overt conflict in the primitively eusocial wasp Ropalidia marginata. PNAS. info:/10.1073/pnas.1212698109
Most people with synesthesia can't tell you exactly why they perceive the letter M as purple and not orange, or a high C-sharp as bright yellow and not blue. For one group of synesthetes, though, there appears to be an answer. For their green D's, red G's, and so on, they can thank the toy company Fisher-Price.
Stanford researchers Nathan Witthoft and Jonathan Winawer discovered, through word of mouth and from synesthetes contacting them online, a group of people who share a "startlingly similar" set of letter-color associations. Out of the eleven subjects, ten remembered owning (or still owned) a particular set of alphabet refrigerator magnets that was manufactured in the 1970s and 1980s.
The leftmost column below (labeled "set") shows the actual colors of this toy. The colors that the eleven subjects associate with the alphabet are listed as S1 through S11, in order of how well they match the magnetic letters. (And to the right are the magnets themselves.)
Subject S1 was carrying around mentally a perfect replica of the Fisher-Price letters, as the authors report in Psychological Science. The others had some differences—but were close enough to the toy's colors that, the researchers figure, it can't be a coincidence.
All eleven subjects also had number-color synesthesia. For the numerals 0 through 9, five of these people turned out to have color associations that matched sets of magnetic numbers sold along with some Fisher-Price alphabet sets.
Witthoft and Winawer don't think the magnets themselves made anybody synesthetic. But among this group of people who became synesthetic (and they may have been predisposed; it runs in families), many of the associations they learned came from a childhood toy.
Not that synesthesia should be confused with memory. Someone with synesthesia doesn't recall the color green when he sees the letter K the same way he sees Kansas and recalls that Topeka is the capital. Instead, synesthetes automatically experience that color when they read that letter or number (or experience a taste when they hear a sound, among other rarer combinations). Some even see the color on the page.
The authors say that the case of the Fisher-Price magnets shows synesthetic associations can be learned, rather than plucked from nowhere by the brain. "The idea that the colors would be learned has been around for a long time," Witthoft says, "but it has been difficult to turn up any examples." In this case, a mass-produced toy—combined with the powers of the Internet—helped.
But they don't think most synesthetes learn their associations from objects around them. These people appear to be, the researchers write, "anomalies among the anomalous."
When the colors of these subjects' mental alphabets differed from the Fisher-Price letters, it was often in ways that made them less anomalous—that is, more like the synesthetic population in general. "Color-grapheme synesthetes as a group have some shared tendencies," Witthoft says.
For example, 40 to 50 percent of English-speaking synesthetes associate the letter Y with yellow. Out of three subjects in this study who deviated from the red Y of the magnets, two went to yellow. It's also common to associate the letter X with black, as four subjects did (deviating from Fisher-Price purple).
Besides yellow Y's, studies have also found a lot of red R's, blue B's, and violet V's among synesthetes. These associations seem to come from language. The origin of most connections, though, is still mysterious.
One study, Witthoft says, argues that the brightness of a synesthetic color is related to how common that letter or number is. Other research "suggests that letters with similar shapes end up with similar colors." And in some types of synesthesia, he says, there are hints that the associations come from some basic way the brain is set up. For example, "pitch-color" synesthetes tend to see higher pitches as brighter colors. Non-synesthetes, if asked, make the same connection.
For now, childhood toys seem to be only a small part of the answer. To help dispel more of the mystery, you can take tests for synesthesia at synesthete.org—even if you weren't a Fisher-Price kid.
Witthoft, N., & Winawer, J. (2013). Learning, Memory, and Synesthesia Psychological Science DOI: 10.1177/0956797612452573
Images: Manon Paradis (Flickr); Witthoft & Winawer.
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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
Image: Sea urchins, courtesy of New Zealand-American Submarine Ring of Fire 2005 Exploration, NOAA Vents Program.
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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
If you ask most heterosexual people what height they're looking for in a partner, they'll describe basically what a children's-book illustrator would draw: the man taller than the woman but not towering over her. But those of us who aren't pen-and-paper must settle for real human partners in human shapes and sizes. Nevertheless, new research says most people end up with a reality that matches the fantasy.
Researchers led by Gert Stulp of the University of Groningen in the Netherlands wondered whether people's professed height preferences matched who they ended up with. Earlier studies had shown that within Western cultures, there are clear trends: Taller people are interested in other tall people; shorter people like short people. And both sexes prefer that the male be taller.
But not too tall! One study combed through thousands of personal ads from a dating site that let users indicate the tallest and shortest person they'd consider dating. On average, women said they weren't interested in men more than 17% taller than themselves. For a 5-foot-5 woman, for example, that means a man over 6 foot 4 seems like a little much.
To compare these preferences to a real population, Stulp and his coauthors used data from the Millennium Cohort Study, a broad sampling of almost 19,000 babies born in the United Kingdom in the year 2000. Among other things, the parents of these babies had been asked for their heights, and 12,502 couples had answered the question.
To see what it would look like if people paired off with no regard to height, the researchers created 10,000 random reshufflings of their UK couples. They then compared these chance pairings to reality.
First, they tested whether people seek out their own kind. Sure enough, taller people had taller partners, and shorter people had shorter partners.
The next question was whether people really care about the man being taller. Of course, since men are on average taller than women, randomly pairing people off is likely to get you a taller male anyway. In the randomized UK couples, the male was taller 89.8% of the time. But in reality, 92.5% of couples had a taller male, a significant difference. And when the woman was taller, it was likely to be only by a tiny bit.
Finally, people say they prefer height differences that aren't too exaggerated. But do they follow through? The authors looked for height gaps of 25 centimeters or more. In the random pairings, this occurred in 15.7% of couples. But in real life, only 13.9% of couples had a height difference this huge.
More often than chance would predict, these couples had followed traditional height preferences. That suggests that when we choose our partners, height does matter.
The study doesn't address the preferences (or reality) of couples who are not heterosexual, not parents, or not in the United Kingdom. Stulp says research has shown that across Western cultures, heterosexual people report very similar preferences for a partner's height. (The Netherlands, where the 6-foot-7 Stulp lives, is home to the tallest people in the world. But he says he believes height preferences in this land of giants are the same, just shifted upward.) In non-Western cultures, he says, those preferences are slightly different and more variable.
Stulp, in fact, was surprised that height preferences didn't have an even stronger affect on the results. He expected reality to be further from random chance than it was. But, writing in PLOS ONE, he acknowledges that many factors affect our choice of partner. "Height," he writes, "is but one of many characteristics valued in a mate."
Stulp, G., Buunk, A., Pollet, T., Nettle, D., & Verhulst, S. (2013). Are Human Mating Preferences with Respect to Height Reflected in Actual Pairings? PLoS ONE, 8 (1) DOI: 10.1371/journal.pone.0054186
Image: Peter Rukavina (Flickr)
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Stulp, G., Buunk, A., Pollet, T., Nettle, D., & Verhulst, S. (2013) Are Human Mating Preferences with Respect to Height Reflected in Actual Pairings?. PLoS ONE, 8(1). DOI: 10.1371/journal.pone.0054186
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.
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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
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.
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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
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)
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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
Peering into the past life of this fossil took an x-ray scanner powered by a particle accelerator. What scientists saw there was mysterious: an ancient lizard had left behind its skin and teeth, but none of its bones. To tell the ghost's tale, they relied on some very modern equipment.
At Stanford University, an accelerator called a synchrotron sends electrons zipping around a track fast enough that x-rays spin off of them. These x-rays are collected into an extremely bright x-ray beam that scientists can use for various projects. One application, x-ray fluorescence, lets researchers map the actual chemical elements inside on object.
Other methods of analyzing an item's chemical makeup require scientists to focus on tiny slices, destroy their samples entirely, or creep along at a rate of one square centimeter a day. But the setup at Stanford lets scientists look quickly and thoroughly at larger objects while keeping them in one piece. The synchrotron has previously been used to reveal writings of Archimedes that were scraped away and painted over, and to deduce the pattern on the feathers of the 120-million-year-old Confuciusornis.
University of Manchester paleobiologist Phillip Manning and his colleagues, who had worked on scanning Confuciusornis and other fossils, now turned the synchrotron's powerful x-ray beam onto an unusual fossil. The 50-million-year-old lizard specimen comes from Colorado. What's unusual is that the animal's skin is beautifully preserved, right down to the scales—but the skeleton is gone.
Scanning the fossil for sulfur (in the photo above) or copper produced ghostly silhouettes of the lizard's whole body, since these elements are naturally present in trace amounts throughout an organism. Tuning their scans for phosphorous brought a surprise: dots popped out of the lizard's ghostly head in the shape of a jaw.
In the image above, green is a map of sulfur in the head and neck (check out the scales!). Phosphorous and magnesium are overlaid in red and blue. The authors write that this chemistry is "typical for biomineralized structures." A close look revealed two overlapping bites: a full set of lizard teeth.
Before the synchrotron scanning, researchers thought the unusual Colorado fossil was a 50-million-year-old molted lizard skin. But even animals that shed their skin don't tend to leave behind their entire jaws when they do so. This animal died in one piece.
Although bones and teeth have similar ingredients, the authors write that the structure of teeth makes them more resistant to dissolving. But how did the delicate skin stay intact? "If the acidity of the ground waters are high, bone would be vulnerable," Manning says. "However, high acidity is often helpful in 'tanning' skin to preserve [it]. Think bog bodies from northern Europe."
As researchers continue to peer into the past with the synchrotron, Manning is narrating their progress at his blog. He doesn't anticipate running out of subjects. "We have a few million life forms to wade through," he says. In other words, there are plenty of ghosts of fossils yet to come.
Edwards, N., Wogelius, R., Bergmann, U., Larson, P., Sellers, W., & Manning, P. (2012). Mapping prehistoric ghosts in the synchrotron Applied Physics A DOI: 10.1007/s00339-012-7484-3
Images: Edwards et al.
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Space travel for regular folks is almost here. But before jumping on board the nearest spacecraft, amateur astronauts and their doctors might want to consider the health risks. Although standard air travel is more boring than spaceflight, it's also less likely to shrink your bones or deform your eyeballs.
"Practically only the healthiest people have flown in space so far," says Marlene Grenon, a vascular surgeon at UCSF who researches the effects of microgravity on the body. Government astronauts go through extensive medical testing and training. But even these extra-fit fliers have suffered ailments ranging from cardiac dysrhythmia to good old-fashioned vomiting. What's in store for the rest of us?
Grenon is the lead author of a paper in BMJ asking that question. The researchers say that doctors will have plenty to consider before sending their patients to boldly go where no civilian has gone before.
"Space motion sickness would be expected to be the most common" medical problem, Grenon says, "particularly for short-duration flights." If your inner ear is easily confused by sitting still in a moving vehicle, just imagine what happens when that vehicle has no up or down.* NASA's parabolic flights—trips on aircraft that fly in steep up-and-down waves, simulating weightlessness for astronauts in training and scientists researching low gravity—have earned the nickname "vomit comets" for a reason.
Life without gravity is hard on the bones and muscles as well as the barf reflex. NASA astronauts onboard the space station exercise for two hours every day to counteract bone loss, muscle atrophy, and a decrease in cardiovascular fitness. Grenon says she doesn't yet know how weightlessness might act on people who are less fit to begin with, or overweight.
Exercise may prevent muscle atrophy but it doesn't do much for squished eyeballs. A study last year found that after a six-month space mission, astronauts were likely to have "flattened globes" and other eye problems. The shifting of fluids inside the head, free to bounce off the walls just like the astronauts themselves, might be to blame. Even after shorter trips, many astronauts reported worsened eyesight.
The authors of the new paper name several medical conditions that might worsen in microgravity. For people with diseases of the blood vessels, fluids drifting around might be dangerous. Aneurysms could rupture during takeoff. Bone loss in space could be especially bad for people who already have osteoporosis. Acid reflux could worsen when the esophagus no longer knows which way is up. And don't forget radiation exposure.
But the most ordinary complaint that might ground you is an infection. Grenon writes that even people with simple ear or skin infections should consider postponing trips to space.
That's because the immune system changes during spaceflight, Grenon says. Although these changes are not well understood, they "could place the spaceflight participants at higher risk of infection." Additionally, she says, "Some research has also hinted [at] the fact that bacteria grow stronger in microgravity." And radiation might make people more susceptible to infection—or make bacteria mutate more quickly. Overall, the changes in space favor bacteria over your immune system. These risks would be greater on longer flights.
Still want to fly? Virgin Galactic is accepting reservations. If you're willing to put down $200,000 up front, you can still get a spot on their first round of flights. For a cool million you can reserve a private trip for yourself and five friends—that's a buy-five-spaceflights, get-one-free deal. Make sure you pack enough barf bags.
Grenon, S., Saary, J., Gray, G., Vanderploeg, J., & Hughes-Fulford, M. (2012). Can I take a space flight? Considerations for doctors BMJ, 345 (dec13 8) DOI: 10.1136/bmj.e8124
Image: U.S. Air Force
*For an exceedingly thorough discussion of space barfing, as well as other bodily functions performed in microgravity, I recommend Mary Roach's book Packing for Mars.
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Grenon, S., Saary, J., Gray, G., Vanderploeg, J., & Hughes-Fulford, M. (2012) Can I take a space flight? Considerations for doctors. BMJ, 345(dec13 8). DOI: 10.1136/bmj.e8124
Think mosquitos have a special fondness for you? Do they choose to target you over adjacent humans? No matter how badly you have it, things might be worse if you were infected with malaria. New research in birds shows that malaria parasites somehow make their victims more attractive to mosquitos. After all, the parasite needs a lift to its next destination—so it forces its sick host to flag down a ride.
Malaria, one of the top killers worldwide among infectious diseases, isn't caused by a virus or a bacterium. The culprit is a one-celled protozoan, called Plasmodium, that comes in a couple hundred disease-causing flavors. Plasmodium falciparum is the species that causes most malaria deaths in humans.
Various other Plasmodium species infect birds, reptiles, and mammals ranging from apes to anteaters. Whichever animal it prefers, the parasite needs to travel to new hosts via the belly of a mosquito. If possible, Plasmodium shouldn't just rely on chance—it should encourage mosquitos to bite its host.
In a 2005 study, researchers found hints that mosquitos are more attracted to the smell of a malarial child than a healthy one. (This was only true once the parasite had reached the right life-cycle stage for spreading to other people.) Giving malaria to kids is hard to justify ethically, though, even if you then treat them with antimalarials as those researchers did.
To pursue the question without leaving behind a trail of sick children, researchers in France turned to birds. Author Stéphane Cornet, of the Centre d'Ecologie Fonctionnelle et Evolutive, says the avian malaria parasite the team used infects more than 30 bird species around the world. For their experiments, they used canaries.
Mosquitos could prefer sick animals simply because they're easy targets. "Infection often renders hosts lethargic, as we are when we feel sick," Cornet says, "so that they are less able to defend themsleves against [mosquito] attacks." But he and his coauthors were more interested in whether malaria changes the particular bouquet of an animal to tempt to passing mosquitos. So they placed all their canaries inside PVC tubes with only their legs sticking out. This way, the birds' behavior and appearance wouldn't matter.
Fifty canaries were divided into pairs. Then the researchers released 70 hungry female mosquitos into a cage with each pair of birds (or, from the mosquitos' perspective, a cage holding four bird legs). After the mosquitos had feasted, the authors checked the DNA of the blood in their bellies to find out which bird each mosquito had chosen. Every mosquito choice test was repeated three times.
After testing mosquitos on healthy birds, the researchers infected one bird in each pair with avian malaria and repeated the tests 10-13 days later, when the birds were sickest. Two weeks after that, they tested the mosquitos and birds a final time. By then, 9 birds had died. But the surviving infected birds had entered the "chronic" stage of infection, when the parasite lies low and the victim isn't as sick.
Mosquitos weren't any more interested in acutely ill birds than in healthy birds, the researchers found. This might have been because the malaria had driven down their red blood cell counts, making their blood less delicious to mosquitos. But once the canaries entered the chronic stage of malaria, mosquitos clearly preferred to feed on the infected birds. The authors report their findings in Ecology Letters.
Cornet believes malarial birds give off some signal to attract mosquitos, such as extra carbon dioxide or a specific odor. What exactly that signal is, and how the Plasmodium parasite manipulates its host into sending the signal, remains a mystery.
A canary is of course not a person, and their malaria parasites are different from ours as well. But there are similarities in how the two parasites act on their hosts, Cornet says. Humans, like birds, might give off some mosquito-enticing perfume when infected with malaria. Finding this perfume could help prevent malaria transmission in the future. And even before that happens, Cornet says, it's useful for people who model the spread of malaria to know that mosquitos aren't choosing their victims randomly.
If you're still feeling resentful toward mosquitos, it may help to know that the malaria "perfume" is really a trap. Mosquitos that carry Plasmodium parasites are about a third less fertile than they would be otherwise, another study this year found. Drinking from infected hosts is bad for mosquitos just like it's bad for the next animal they bite. But, like us, they're helpless to Plasmodium's wiles.
Cornet, S., Nicot, A., Rivero, A., & Gandon, S. (2012). Malaria infection increases bird attractiveness to uninfected mosquitoes Ecology Letters DOI: 10.1111/ele.12041
Image: Travis S. (Flickr)
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Cornet, S., Nicot, A., Rivero, A., & Gandon, S. (2012) Malaria infection increases bird attractiveness to uninfected mosquitoes. Ecology Letters. DOI: 10.1111/ele.12041
Covering yourself with garbage is a great way to look less delicious to predators. More than a hundred million years ago, one insect species took this strategy to the extreme by growing a kind of giant trash can on its back. Scientists could identify the new species thanks to a remarkable specimen that was preserved—along with an informative topping of trash—in amber.
The insect that kindly died in a blob of tree resin in early-Cretaceous Spain was a young green lacewing. Modern-day green lacewings are predatory insects common in North American and Europe. Before they develop their lacy adult wings, the larvae of some species protect themselves by carrying trash around. They collect plant material, insect carcasses, and other debris in their jaws, then twist their heads around to tangle the material into short appendages growing out of their backs. The trash camouflages them and provides a physical, untasty shield when predators (which can include ants, wasps, and cannibalistic green lacewings) attack.
But the Cretaceous lacewing was so wildly different from its modern-day relatives that scientists named it Hallucinochrysa—that is, an insect bizarre enough to seem like a hallucination. (For its second name they chose diogenesi in honor of Diogenes syndrome, a trash-hoarding disorder in humans. The disorder, in turn, is named after a Greek philosopher who lived in a tub.)
University of Kansas entomologist Michael Engel, one of the authors of the new paper in PNAS, describes the ancient lacewing's trash-carrying apparatus as "dramatic and unique." Unlike the short appendages on modern green lacewings, the old insects grew a thicket of extremely long, hairy tubes from their backs (illustrated above).
Coauthor Ricardo Pérez-de la Fuente, of the University of Barcelona, points out another unusual feature of the trash basket: the tiny hairs growing out of the tubes have "trumpet-shaped endings," which he says would have helped anchor the trash in the basket. Once the refuse was in place, it stayed there.
Almost as exciting as the hallucination-worthy insect was the collection of trash preserved with it. "What attracted our attention since the very beginning was the high density and intricacy of the trash packet," Pérez-de la Fuerte says. Peering into the amber with a microscope, the researchers identified the thread-like plant parts trapped on the insect's back as bits of ferns.
The plants seem to match a tropical group of ferns that, these days, move into areas swept clean by wildfire or lava. Since ancient wildfires also encouraged amber to form, and this particular sample was part of an abundant amber cache, it seems likely that the area had experienced fire. At least one trash-toting insect had filled its basket with bits of the ferns that sprouted afterward. Then this insect carried its garbage collection up into a tree and died.
Since the ferns lived on the forest floor, their remains would have been "extremely unlikely to be found otherwise," says Pérez-de la Fuerta. The day this little trash hoarder walked into a sticky tree was a bad one for the insect, but a very lucky one for scientists.
Ricardo Pérez-de la Fuente, Xavier Delclòs, Enrique Peñalver, Mariela Speranza, Jacek Wierzchos, Carmen Ascaso, & Michael S. Engel (2012). Early evolution and ecology of camouﬂage in insects PNAS : 10.1073/pnas.1213775110
Image: J. A. Peñas
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Ricardo Pérez-de la Fuente, Xavier Delclòs, Enrique Peñalver, Mariela Speranza, Jacek Wierzchos, Carmen Ascaso, & Michael S. Engel. (2012) Early evolution and ecology of camouﬂage in insects. PNAS. info:/10.1073/pnas.1213775110
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