Field of Science


Threat of Death Makes People Go Shopping

Nothing says "Let's hit the outlet mall" like nearly being wiped out by a rocket. A study of both Americans and terrorized Israelis suggests that certain people respond to the threat of death by going shopping. Because if it's your time to go, you may as well be wearing the latest from Forever 21.

Michigan State University marketing professor Ayalla Ruvio and her colleagues performed two studies of potential shoppers. The first took place in Israel. Questionnaires were handed out at a community center in a town just one kilometer from the Gaza Strip, during six months of daily rocket attacks there in 2007. The same surveys were distributed in a second town farther from the fighting, where residents were aware of the violence but not in direct danger. The researchers got back 139 surveys from the first group and 170 from the second.

The questionnaires were meant to ferret out a few different answers about people. Did they experience post-traumatic symptoms such as nightmares or memory loss? Did they cope with negative feelings by buying things? How often did they return from a shopping trip with items they hadn't meant to purchase? Other questions assessed how materialistic the subjects were—did they place a lot of value on owning nice things?

Israelis who were experiencing daily rocket attacks, unsurprisingly, reported more post-traumatic stress. People who felt more stress admitted to more compulsive or impulsive shopping behaviors. And both these effects (feeling stress and going shopping) were stronger in more materialistic people.

For their second study, the researchers used a group of 855 American subjects, meant to be demographically representative of the U.S. population overall. Subjects filled out an online survey that measured their materialism, shopping habits, and how much they thought about their own death, as well as other factors. Once again, for people who were more materialistic, there was a relationship between fear of death and impulse buying.

Because the more materialistic Israelis experienced more stress, the researchers think "materialism makes bad events even worse." And when materialistic people feel threatened, they buy things they don't really want (or maybe can't afford).

The findings don't only apply to people living in the Middle East. Events that make people fear for their lives can include car accidents, assaults, and natural disasters. Yet Ruvio puts a positive spin on the ubiquity of trauma. "This presents an opportunity for both manufacturers of impulse items and the retailers that sell these products," she writes. When a severe storm or a military crisis is brewing, she suggests stores put their high-profit-margin items up front where impulse shoppers will see them.

While retailers may be able to benefit from people's crises, shoppers themselves won't. Previous research, Ruvio writes, shows that "most materialistic individuals derive little satisfaction from their consumption activities." So much for retail therapy.

Image: by Ian Freimuth (via Flickr)

Ayalla Ruvio, Eli Somer, & Aric Rindfleisch (2013). When bad gets worse: the amplifying effect of materialism on traumatic stress and maladaptive consumption. Journal of the Academy of Marketing Science DOI: 10.1007/s11747-013-0345-6

Coloring In Birds' Bellies with Magic Marker Makes Them Healthier

Remember when you were a kid and the magic marker boxes always had some sort of really elaborate drawing on the back? As if to say, "Buy these eight wide-tip Mr. Sketches and you, too, will be able to create a photorealistic portrait of a scarlet macaw"? But when you bought the markers and tried to copy the picture, it always came out as a stupid magic marker bird? You might have gotten more realistic results by coloring directly on a real animal. Some scientists tried this, and changed the birds' entire quality of life.

In North American barn swallows (Hirundo rustica erythrogaster), males and females with darker-tinted bellies are able to have more young. But they don't get their tan tummies by lying in a UV bed. The birds develop their color months before the breeding season starts, and it depends on both genetics and their health at the time.

Biologists call dark bellies on barn swallows an "ornament," like long tails or showy sets of antlers in other species. These traits may not serve a practical purpose, but they can advertise to potential mates how healthy or hardy the animal lugging that long tail around is.

Ecologist Maren Vitousek at the University of Colorado, Boulder, and her colleagues wanted to know whether barn swallows' ornamental belly feathers could also work in the other direction. A bird's health or fitness affects the color of the feathers—but can the color of the feathers also affect the bird's health?

The researchers captured 60 female barn swallows in Colorado, shortly before the time of year when the birds would be pairing off with mates. Using marker, they colored in the entire belly area of half the birds. The shade—PrismaColor light walnut no. 3507—was within the natural range of hues for barn swallows. Then the scientists sent the newly made-over birds back out into the world.

About a week later, the scientists began to recapture the birds. (They found 36 out of the original 60.) Ordinary, uncolored birds had higher levels of oxidative damage in their blood than when they were first captured. Their bodies had been under stress. But birds with darkened feathers actually had less oxidative damage than before.

Vitousek, who's now at Cornell University, thinks coloring in female birds' belly feathers made their lives easier. "Darker plumage may signal social status in barn swallows," as it does in some similar birds, she says. If so, other birds may have judged their tanned peers to be of higher status, and possibly more likely to win a fight. "As a result, they may be challenged less," she says.

Even though birds or other animals sometimes develop their showy traits well before the mating season, this kind of feedback loop would let these traits remain honest signals of how healthy an animal is. Fitter birds make darker feathers, and darker feathers seem to keep birds healthier by sparing them harassment. "What we are finding is that the appearance of an individual alone can also influence physiological state—and probably fitness—by changing social interactions," Vitousek says.

And all it takes to change a bird's social status is a quick pass with magic marker. Maybe it can be a post-retirement hobby for that Mr. Sketch package artist.

Maren N. Vitousek, Rosemary A. Stewart, & Rebecca J. Safran (2013). Female plumage colour influences seasonal oxidative damage and testosterone profiles in a songbird. Biology Letters DOI: 10.1098/rsbl.2013.0539

Image: by Walter Siegmund (via Wikimedia Commons)

This post has been submitted to the 2013 blog contest held by the National Evolutionary Synthesis Center (NESCent).

Farmer Slime Molds Carry Pest-Killing Friends to Protect Their Crop

Even single-celled farmers have to protect their crop from hungry mouths. That's why slime molds carry certain toxic bacteria inside their bodies on their way to farming others in the soil. Like living Roundup, these bacteria harm competitors while helping their farmer hosts to survive and even thrive.

Slime molds start out life as one-celled amoebae, living in soil or mulch and munching their way through the bacteria there. Once food becomes scarce, they seek each other out and glom together into big, gooey colonies. Some species form blobs that are big enough to see with your naked eye as they ooze across a forest floor in search of greener pastures. Individuals in the blob may use their bodies to build stalks, lifting other individuals as spores. These travelers will be carried away by the wind to start over someplace new.

Dictyostelium discoideum amoebae, when they set out into the world as spores, don't go unprepared. Debra Brock, a PhD student at Rice University at the time, announced in 2011 that some slime molds are farmers. Before the last of the food runs out, they tuck a few edible bacteria into their bodies. Then they launch themselves into the wind, and when they land they seed the soil with the crop they've been carrying.

Brock found that about a third of wild Dictyostelium discoideum slime molds are farmers. But if this is true, how do they deal with moochers? Farmers pay a price for their pastime—they have to set aside the last bit of available bacteria instead of eating it. If their neighboring amoebae can eat all the food they want, then live off the bacteria crop that farmers plant in a new location, why aren't farmers at a major disadvantage?

Brock, who's now a research scientist at Washington University in St. Louis, may have found the answer by digging deeper into the pockets of the amoebae. Farmers don't only carry food with them when they disperse, she saw: they also carry inedible bacteria. Once everyone makes their way to a new plot of land, could these bacteria somehow be protecting their hosts from moochers?

To find out, she mixed farmers and non-farmers together in dishes with plenty of food bacteria—and added a little sprinkle of the inedible pocket bacteria. Farmers stayed perfectly healthy. But non-farmers suffered, producing only half as many spores as usual.

Next Brock spun down samples of the inedible bacteria to extract a liquid from them, which would contain any chemicals the bacteria give off. When she gave doses of this liquid to both farmer and non-farmer amoebae, the non-farmers suffered again. Not only were the farmers fine, but they actually benefited, producing more spores than when they were dosed with a control liquid.

Finally, farmers and non-farmers were grown together and allowed to compete, along with a few species of bacteria that the farmers had carried with them. The more farmers there were, the worse non-farmers fared.

The Dictyostelium discoideum individuals that opt for a farming lifestyle seem to keep deadbeats away by bringing other bacteria with them. Brock doesn't know what weapon these bacteria give off that's bad for non-farmers. But she speculates that the system may have evolved because certain slime molds were genetically predisposed to gather up bacteria before traveling. These farmers would have been likely to vacuum up toxic bacteria along with the edible ones. By developing a resistance to the toxin—and even a way to benefit from it—the slime molds found a way to make farming profitable.

Image: Dictyostelium aggregation, by Bruno in Columbus (via Wikimedia Commons)

Debra A. Brock, Silven Read, Alona Bozhchenko, David C. Queller, & Joan E. Strassmann (2013). Social amoeba farmers carry defensive symbionts to protect and privatize their crops. Nature Communications DOI: 10.1038/ncomms3385

Field Guide to Arachnophobic Entomologists

Working with bugs professionally, it turns out, does not make you immune to the jeebies. A survey by American Entomologist magazine found that arachnophobic entomologists do exist. They're not even  that hard to find, if you're willing to turn over a few rocks.

Here are the most common types of spider-fearing entomologists that have been described thus far, so you can recognize them in the field:

Bad with Numbers

The survey, performed by retired spider researcher Richard Vetter, turned up 41 working entomologists who are afraid of spiders (or at least averse to them). Fifteen agreed with the statement "Spiders are one of my worst fears."

On a list of things about spiders that might bother them, more than half of the fearful entomologists said "many legs" was an important trait. Flies or cockroaches or centipedes might be no problem, but eight legs is, apparently, crossing a line.

One forensic entomologist in the survey works with maggots, and said that she "would rather pick up a handful of maggots than have to get close enough to a spider to kill it." That's a hard statement to sympathize with, but at least her anti-legs bias is consistent.

Family Blaming

"Several respondents stated that family members tormented them with spiders," Vetter writes, perhaps contributing to the development of their fear. In survey respondents, just like in the general population, arachnophobia usually arose in childhood.

One entomologist's parents warned her at an early age—when she had the chance to hold a tarantula at an exhibit—that spiders are dangerous. She may have accepted their lesson a little too well, because her survey responses put her in the range of clinical arachnophobia. Another subject's parents tried to instill an appreciation of spiders, explaining that they're good and helpful bugs—but the message must have gotten distorted somewhere.

Siblings received some blame too. One entomologist said that when she was six, her older sister used to chase her around the house holding dead spiders in tissues. Of the preserved spider collection she manages at a museum, she says, "They still give me the jeebies."

Prone to Traumatizing Events

Some people traced their fear to an especially upsetting event. One woman had watched an egg sac hatch on her mattress, releasing baby spiders everywhere. (Her father had also teased her with a large spider when she was younger.) Today her arachnophobia is so strong she has considered therapy, but prefers to just avoid looking at pictures or passing in front of posters of spiders. One imagines this is difficult for an entomologist.

Another respondent shared a uniquely harrowing tale, though it happened well after his arachnophobia had developed. He was driving a van at night, he said, when a yellow sac spider ran across the inside of his windshield:
"It disappeared, and, in a few seconds of utter, shocking horror for me, began running over my face and into one of my nostrils. Somehow maintaining control of the vehicle, I snorted out with all my force, and dislodged it. After finding a place to park and collect my wits, I searched the van in vain for almost an hour, before giving up and getting back on the road. That was not a good day."

Totally Normal

Although "many legs" was a common reason people in the survey gave for hating spiders, even more popular answers were "way they move," "fast running" and "unexpected." (Another popular one was "they bite," even though several respondents work with bees or wasps and apparently aren't scared of stings.)

Spiders probably aren't anyone's favorite surprise. And in fact, Vetter found that arachnophobic entomologists are pretty much like any other arachnophobes. Their fears develop early on, and persist even if they're clearly irrational. Like phobic entomologists, arachnophobes in the general public may hate particular spider traits such as their unpredictability, jerky walking style, or hairiness.

Unlike garden-variety arachnophobes, though, arachnophobic entomologists happily devote their careers to other creepy-crawlies. They don't find anything gross about bugs in general—as long as those bugs have the right number of legs.

Vetter, Richard S. "Arachnophobic Entomologists: When Two More Legs Makes a Big Difference." American Entomologist Fall 2013 (171-177).

For Diguise, Female Squid Turn On Fake Testes

The best way to stay out of trouble, if you're a shimmery, color-changing little squid, might be to paint on some pretend testes. Scientists have found that certain female squid can switch on and off a body pattern that makes them look male. They use a never-before-seen cell type to do it, and it may be all for the sake of keeping the actual testes owners far away.

The opalescent inshore squid, Doryteuthis opalescens, lives in the Eastern Pacific and is one of the main species caught for food in the United States. So you'd think someone would have noticed its trick before. But the animals shift their colors all the time, and no one seems to have paid much attention to a certain bright stripe particular to females.

Daniel DeMartini, a graduate student at the University of California, Santa Barbara, "observed the female squid rapidly switching the stripe on and off," says his advisor, Daniel Morse. He decided to gather a few hundred D. opalescens squid in laboratory tanks and watch them work.

DeMartini found that females can opt to turn on a bright white stripe on their mantles, highlighted by a line of iridescence on both sides. This happens to look pretty similar to a male squid's testis, which—in his less colorful moments—is visible as a long white shape inside his transparent body.

The authors speculate that female squid might use this stripe as a disguise when they want to avoid harassment by males. "In this species of squid, mating occurs in dense assemblages of animals, with the females subject to repeated bouts of mating by multiple males," Morse says. By switching on her white stripe and mimicking a male, a lady squid might be able to fend off some of these mating attempts, protecting both herself and any fertilized eggs she's carrying.

Morse is less excited about this act of deception, though, than he is about the cells that squid use to pull it off. Within the white stripe region, specialized cells hold proteins called reflectins inside many spherical packages. These proteins start out colorless. Upon receiving a signal from the brain, the packages shrink into dense blobs. The varying sizes of the blobs make them reflect all different wavelengths of light, so that the cells as a whole appear bright white. It's the same way we humans make white paint, Morse says: small, dense particles of titanium dioxide are suspended in the liquid, and the combination of different-sized particles ensures all light waves are reflected at once.

Earlier, the authors found reflectins in the same squid's color-changing cells. Instead of turning from transparent to white, these cells can move between many different colors. In this case, "the reflectins are packed in accordion-like folds or pleats in the cell membrane," Morse says. When the brain tells the proteins to clump together, the accordion folds close up—and depending how far they close, the cells will reflect different wavelengths of light, from red all the way to blue.

It's fitting that squid have ten arms, because this one seems to have a surprise up every sleeve. As to whether it's still hiding anything more surprising than fake testes, we'll have to wait and see.

Daniel G. DeMartini, Amitabh Ghoshal, Erica Pandolfi, Aaron T. Weaver, Mary Baum, & Daniel E. Morse (2013). Dynamic biophotonics: female squid exhibit sexually dimorphic tunable leucophores and iridocytes. Journal of Experimental Biology : 10.1242/​jeb.090415

Images: DeMartini et al. (Top: a close-up view of an iridescent stripe in a female.)

How Many Continents Does Katy Perry's "Roar" Video Take Place On Simultaneously?

The video for Katy Perry's newest single, "Roar," has been viewed almost 36 million times since it appeared online four days ago. In case none of those views were yours, a quick plot summary: A woman crash-lands in the jungle with an attractive but inconsiderate boyfriend in safari gear who's eaten by a tiger at 0:40. She's scared at first, but soon befriends a monkey, is bathed by a helpful elephant, and changes out of her old clothes into (spoiler alert!) a leopard bra. And sings.

On her road to empowerment, Katy gets help from a diverse array of animals. So diverse, in fact, that their being together in the jungle might be the most fantastical element of the video.

First there's the monkey, seen above inspiring Katy to turn her stiletto* into a spear. It's a capuchin, native to Central and South America.

What about the beast that disposed of the boyfriend? Katy sings "I've got the eye of the tiger," and she's got the whole body of it in her video. But tigers live only in Asia, so either the big cat or the monkey seems to have taken a wrong turn across an ocean somewhere.

Elephants can live in Asia as well, so maybe Katy's pachyderm friend (who does double duty as shower head and clothes hook) is in the right place. Asian elephants, though, have distinctively small ears that sit low on their heads. The fellows with the big flapping ears—on full display in the picture at the bottom of this page—are African elephants.

So now we're up to three landmasses at once. Perhaps this bird can settle the tie: it looks like a great hornbill, a tropical bird from Asia.

Then there's the creature whose teeth Katy is brushing in this scene. Its short and rounded snout, unlike a crocodile's long, pointed one, suggests it's an alligator. That's one more point for the Americas. (A crocodile's bottom teeth also protrude when its mouth is closed, while a gator's don't. But this prop only appears in the video with its mouth wide open. It may not have a hinge.) 

A crocodile would have given another point to Africa. Sorry, cradle of civilization! But wait—sneaking into the frame during the final seconds of the video is a baboon, a monkey that lives only in Africa (except for a desert-dwelling species in the southern tip of the Arabian Peninsula).

To break the three-way tie between continents, let's go back and take a closer look at the birds in the video. There are a couple of macaws, the striking parrots from Central and South America:

And key to the plot of the whole video is this red bird. Katy uses its feathers to build a lure that tempts the tiger, which she ultimately subdues in a roar-off and turns into her pet.

The red bird also provides a plot twist for our purposes. I sent the picture to ornithologist and Guardian blogger GrrlScientist for identification. "Oh wow," she wrote back, "a female eclectus parrot." The males are bright green with orange beaks, looking like a different species altogether. Eclectus parrots don't live alongside the capuchin, the elephant, or the tiger: they're native to northeastern Australia, New Guinea, and neighboring islands.

At least four parts of the world, then, are represented in Katy's jungle. (Don't worry about the leopard bra—our heroine fashioned it out of a scarf she was wearing on the plane.) It's a little surprising not to see a lion in the video, since it's the only animal aside from the tiger that actually appears in the song's lyrics. But then again, lions prefer the savanna to the forest. Maybe that would have been too unrealistic.

*I'm not sure of the species of shoe.

Images: screenshots from "Katy Perry - Roar."

Male Frogs Grip Mates with Pheromone-Injecting Thumb Spikes

There's nothing subtle about the wooing of European common frogs. Males grow spiny pads on their thumbs during the breeding season, the better to grip their mates. As if that weren't enough, the pads also seem to channel pheromones out of a frog's hands and straight into his female partner's body.

Frogs fertilize their eggs out in the open, so you might think there'd be no need for all this effort. Yet males of most frog species can be seen during the mating season "taking a piggyback ride" on their mates, as a group of scientists in Belgium euphemistically puts it. Technically called amplexus, the male-on-top position allows him to fertilize the eggs just as the female sends them out of her body.

In some frog and salamander species, males further ensure their success by temporarily growing tough, often spiky pads on their forearms or thumbs. Earlier research discovered glands of some sort sitting beneath these pads, but it wasn't clear what the glands did. So the scientists in Belgium decided to take a closer look at the hands of one such animal: Rana temporaria, the European common frog.

The scientists used micro-CT scanning to build a 3D image of a male frog's thumb pad. They saw that glands underneath the pad led to ducts, which traveled up through the pad to pores on its surface. It appeared that the grippy gloves donned by males for the mating season were also some sort of delivery system.

But what were they delivering? An analysis of proteins in the glands turned up a group of molecules the authors dubbed "amplexins." They're in the same family as certain proteins found in male mammals' reproductive organs, as well as a courtship pheromone in salamanders. In humans, proteins from this family help regulate how eggs and sperm interact.

Comparing thumb pads in the breeding season to shrunken-back thumb pads during the rest of the year, the scientists saw that amplexin production suddenly dropped off near the end of the breeding season. During the rest of the year, the frogs didn't make amplexins at all.

A male who's already got his hooks—literally—into his partner probably doesn't need to worry about courtship. But the authors speculate that amplexins in these frogs might be pheromones that speed up the mating process. Female frogs' chests are often scraped and scratched by their mates' spiny thumb pads, and this may be how a male delivers the pheromones to his partner: straight into her circulatory system.

Hey, it works for Cupid and his arrows. Female frogs, though, would probably give this system two thumbs down.

Image: by Erik Paterson (via Flickr)

Bert Willaert, Franky Bossuyt, Sunita Janssenswillen, Dominique Adriaens, Geert Baggerman, Severine Matthijs, Elin Pauwels, Paul Proost, Arent Raepsaet, Liliane Schoofs, Gwij Stegen, Dag Treer, Luc Van Hoorebeke, Wim Vandebergh, & Ines Van Bocxlaer (2013). Frog nuptial pads secrete mating season-specific proteins related to salamander pheromones Journal of Experimental Biology DOI: 10.1242/jeb.086363

On the Road with Crabs

I'm still on the road, so there won't be any new posts until next week. (One highlight from the trip so far has been a pair of signs we passed in Western New York late at night. The top sign read "CORRECTIONAL FACILITY AREA." Underneath: "DO NOT PICK UP HITCHHIKERS.")

In the meantime, here are a couple favorite travel-related stories from the past.

This Penguin: An Unexpected Journey (January 2013)
Lost baby penguins wearing earmuffs.

Monitoring from Space Shows Even This Giant Crab Can Navigate Better than You (November 2012)
Who doesn't love land crabs?

Another highlight was a radio station we picked up somewhere in Indiana with the tagline, "It's not just a bunch of random songs. It's a bunch of random songs you really like!" See you later this week, by which time I may have adapted that into a new blog descriptor.