Can’t eat poison without dying? Maybe your gut microbes are to blame. Rodents in the Mojave Desert have evolved to eat toxic creosote bushes with the help of specialized gut bacteria. Although scientists had long suspected that bacteria might be key to the rats’ power, they proved it by feeding the rodents antibiotics and ground-up feces.
The desert woodrat or Neotoma lepida lives in dry parts of the western United States. (You might know woodrats as “pack rats”; they build elaborate nests out of debris they’ve hoarded.) In the southern part of the desert woodrat’s range, a bush called creosote grows. Its leaves are coated in a toxic material—the key ingredient, nordihydroguaiaretic acid, normally damages the kidneys and liver of rodents. Yet desert woodrats that live in the creosote bush’s range can eat it without any trouble. In fact, the amount of creosote a desert woodrat eats in just a day would kill a laboratory mouse.
University of Utah biologist Kevin Kohl says it’s “conventional wisdom” that the woodrat’s ability to eat poison comes from the bacteria that live in its gut. But it was difficult to study any animal’s gut microbes before recent advances in DNA sequencing, he says, because most of these bacteria can’t be grown in the lab. Research on gut microbes and toxic foods has usually been done in farm animals, and with just one compound at a time instead of a whole poisonous plant.
Now Kohl captured wild woodrats in Utah to find out what was really happening. Read More
You may have seen headlines over the past week proclaiming that handsome men have lower-quality sperm. If this made you panic because you happen to be a great-looking guy, you can stop. (If you’re an un-handsome man who’s been gloating—sorry.) This scientific study did say a few interesting things about Spaniards, Colombians, and cheekbones. But there was no bad news for good-looking men’s swimmers.
Using male students at the University of Valencia in Spain, researchers searched for connections between good looks and sperm quality. In a 2003 study, the same researchers had already found that more attractive males have better-quality sperm. Now they wanted to confirm that finding while adding a cultural element to the experiment.
After weeding out men with facial hair and various diseases, the researchers were left with 50 subjects. They collected semen samples and photographed the men’s faces from the front and side. The researchers also measured several dimensions of their subjects’ heads that vary between men and women, such as eye size, nostril width, and the proportion of the face that’s below the eyes. Read More
If your grandma got up from the sofa, did a couple toe-touches, and then ran a mile at her college track pace, she might be approaching the athletic skill of a thick-billed murre. These seabirds make incredibly deep, long dives to catch prey. As they age, their bodies slow and change like ours. But the athleticism of their dives never changes—a feat that might help scientists understand the enigmas of aging.
“Most of what we know about aging comes from lab animals,” says Kyle Elliott, a graduate student at the University of Manitoba. These short-lived flies, worms, and mice tell scientists very little about how long-lived wild animals age and die. Even a wild fly or rodent can expect to end its life as another animal’s meal. But when an animal is likely to live for decades, how does its biology change over time? What eventually kills it? Does cancer or poor cardiovascular health change its life expectancy? “There are certainly an awful lot of open questions,” Elliott says.
To find out a little more, he and his colleagues studied the thick-billed murre, Uria lomvia. These auks have black bodies and white bellies like penguins, but live at the opposite end of the earth. They swim and go diving for food in chilly northern oceans. They can travel as deep as 170 meters and stay under for up to 5 minutes, Elliott says, which is “an amazing feat for a 1-kilogram bird.” Read More
There are few more monastic lives in the animal kingdom than a coral’s. In adulthood it gives up swimming to settle on the ocean floor, surround its spineless body with clones, and become a rock. Mouth facing the ocean, it waits passively for whatever drifts by—or maybe not so passively. Taking a closer look at these creatures, scientists have discovered that corals use their tiny bodies to create swirling currents that are relatively enormous. By forcing the ocean water to move molecules closer or farther away, they work to keep themselves alive.
If you could scuba dive down to a hard coral and zoom in to a microscopic view, you’d see the surface covered in the coral animals’ tiny hairs, called cilia. Many people have looked closely at corals before, in fact—even Darwin studied coral reefs while aboard the Beagle. And some scientists have noticed that the waving cilia keep a thin layer of water moving parallel to the coral’s surface—like “a conveyor belt,” says Orr Shapiro, a postdoc at Israel’s Weizmann Institute of Science who studied corals while he was a researcher at MIT.
This simple swishing can help pull food toward a coral animal’s mouth or carry debris away from the coral’s surface. But beyond that, corals seemed to be at the mercy of ocean currents to bring them gases and nutrients that they need and to carry waste products away. Read More
If you watch poker coverage on television, you probably won’t hear the commentators compare players to pigeons. Maybe they should. The birds don’t play a great game of hold ‘em, but the way they think about risk might be strikingly similar to the way we do.
Researchers discovered this by putting humans and birds through a basic study of risky behavior. “In earlier work, we had tried to recreate some classic behavioral economics results with pigeons, but had failed to do so,” says Elliot Ludvig, a psychologist at the University of Warwick. (You might reasonably ask why he’s studying behavioral economics in pigeons. Don’t worry, we’ll get there.)
Humans are famously “risk averse” for gains. This means that if someone offers us a smaller, guaranteed amount of money (or some other reward), we prefer that to an uncertain but larger amount. For example, given a choice between $50 and a coin flip for $100 or nothing, people usually pocket the $50. But we’re “risk seeking” for losses. If the coin flip is between losing $100 and losing nothing, we’ll choose to gamble rather than just handing over $50. The same thing is true when people choose between a larger gain and a smaller one, rather than a gain and a loss, Ludvig says.
This kind of decision making might seem like a stretch for a bird. But even a lowly pigeon has to make choices all the time about where to search for food. The retiree on the park bench with the bag of stale crumbs is a sure bet; following around a child with a tippy ice cream cone is more of a high-stakes gamble.
Yet Ludvig had struggled to recreate human decision-making results in pigeons. The problem, he realized, was that pigeons don’t have the luxury of language. Researchers can explain a gambling scenario to human subjects (“The odds are one-in-three that there’s a new car behind Door Number One!”), but pigeons have to deduce the odds on their own, through trial and error. Rather than teaching pigeons English, Ludvig decided to level the playing field by making humans take a pigeon’s version of the test.
Researchers gathered a group of human subjects and a small group of pigeons. The pigeons did daily testing sessions for about a week. In each trial, a pigeon walked into a testing arena that held a pair of colored doors. After it chose a door to go through, food was dispensed. It was up to the pigeons to learn the pattern: two possible door colors were high-value (orange meant a safe 3 cups of food, and purple was either 4 or 2 cups) and two were low-value (yellow for a safe 1 cup of food, green for a gamble between 2 and 0).
Humans did their trials all at once on a computer screen, with images of colored doors—but like the pigeons, they had to deduce the rules. The reward wasn’t food pellets but a number of points that flashed on the screen after each choice. Researchers told subjects to try to get as many points as possible.
Classic psychology says people should gamble less often when there’s more at stake. What happened, though, was the opposite. By the end of the experiment, when people had figured out the stakes associated with each door, they picked the risky option about 35 percent more often for the high-value door than the low-value one. In other words, they were more likely to gamble for a higher number of points, and to take the safe option for the lower number.
Pigeons made nearly identical choices to humans. By the final days of the experiment, the birds were choosing to gamble more often on high-value doors than low-value ones. The difference was even the same as in humans: about 35 percent.
Why didn’t people behave as expected? Ludvig thinks the difference is that in older studies, subjects had the options spelled out for them. In his study, people had to figure out the odds through their own experience. (Another difference is that the people in this study played for points, not for real monetary rewards or even for food, like the pigeons did.)
When they don’t learn the rules ahead of time, “people behave similarly to pigeons,” Ludvig says. He thinks the results are relevant to real gambling games like slot machines—or even to the choices we make on a daily basis, like whether to risk getting a ticket by parking illegally while we dash into a store.
Ludvig says the close similarity between human and pigeon results surprised him. It may point to something deep and ancestral in the brain that influences our decision making. “We think that a lot of human choice is driven by basic biases about how people perceive and remember risks and rewards, which we share with many other species,” he says.
By studying these biases, Ludvig hopes to learn more about how we make risky choices. Are certain habits—like leaning toward a gamble when the stakes are higher, or lower—exaggerated in people who are problem gamblers or who behave in other risky ways? When humans won’t reveal why they do what they do, a few hungry birds might help.
Image: by Miss Shari (via Flickr)
Ludvig EA, Madan CR, Pisklak JM, & Spetch ML (2014). Reward context determines risky choice in pigeons and humans. Biology letters, 10 (8) PMID: 25165453
Have a great Labor Day weekend, everybody! But be careful not to enjoy yourself too much. (This post on the dangers of laughter first appeared in December 2013.)
Careful with the bedside banter, doctors. Before you put on your best Patch Adams impression, you might want to consider whether your attempts at humor will ease your patient’s discomfort or give him a protruding hernia.
That’s the conclusion of a review paper in the Christmas issue of BMJ that asks the jolly question of whether laughter can kill. The two authors, R. E. Ferner of the University of Birmingham and J. K. Aronson of Oxford University—no JK-ing, those are his real initials—take a tongue-in-cheek approach. They even give their research question an acronym: MIRTH (Methodical Investigation of Risibility, Therapeutic and Harmful).
Ferner and Aronson scoured medical literature for studies having to do with laughter. After “excluding papers on the Caribbean sponge Prosuberites laughlini and with authors called Laughing, Laughter, Laughton, or McLaughlin,” they were left with three categories of study. One had to do with the benefits of laughter, one with its dangers, and the third with medical conditions that have laughter as a symptom.
Let’s hear the bad news first. Read More
A bat’s voice is its livelihood. Chirping and squeaking at just the right frequencies lets it echolocate food and stay alive. Sounding pretty isn’t the point—except when it is. For the first time, scientists think they’ve found a bat species in which females choose mates based on their voices. Even if a lower-frequency squeak might be better for finding prey, males with the highest squeaks are the sexiest.
The horseshoe bats, or Rhinolophidae, are a family of nearly 80 species with bizarre noses. Often generously described as “leaf-shaped,” the nose looks more like a many-layered tree fungus growing out of the bat’s face. The bats live in Europe, Africa, Asia and Australia.
Throughout this family of bats, the larger species make lower-frequency echolocation calls. Think of a tall, barrel-chested bass singer in a choir compared to a smaller tenor (if the whole choir were singing above the range of human hearing, that is.) But one species, Rhinolophus mehelyi, breaks the pattern. Read More
Stalactites hold tight to the ceiling, the saying goes, and stalagmites might grow high enough to reach it. But the simple mnemonic doesn’t come close to covering the variety of weird, rocky shapes growing all over a cave. There are even, it turns out, rocks made from bacteria. They’re not putting the “tight” in “stalactite” so much as the “ack!”
Researchers found the microbe-made rocks in a cave in northern Sweden called Tjuv Antes. (It’s named for a fugitive thief who allegedly hid there in the 1800s.) Therese Sallstedt and Magnus Ivarsson of the University of Southern Denmark’s Nordic Center for Earth Evolution, along with colleagues from Sweden and Spain, saw many kinds of rocky formations in the cave. There were smooth crusts of stone. There were bubbly structures that looked like popcorn. There were structures with delicate fingers like coral (above).
The walls of Tjuv Antes Cave are made of granite. But the researchers only found the stony growths on the cave’s ceiling, which is made of dolerite. There were other things growing on the ceiling too. Read More
You’ve already picked a side in the bird wars, whether or not you know it. As humans carve up formerly empty expanses of the western United States with our roads, electrical towers, and power lines, we’re inadvertently giving a boost to ravens. Meanwhile, the birds of prey that once ruled the land are being left in the dust.
“The ecology of the sagebrush steppe is changing,” says Idaho State University biologist David Delehanty. He means a type of dry, scrubby grassland that’s found in the western part of the country. Raptors used to be the dominant predators here—specifically the buteos, a genus that includes certain hawks and buzzards (and is pronounced “beauty-ohs,” like a very lovely breakfast cereal). These birds have traditionally lorded over the big expanses of arid land.
But in recent decades, raptors have become rarer. Taking their place are common ravens. Read More
Researchers at Disney Research Zurich—who normally work on computer graphics, video manipulation, and animation—recently took a spin in the physical world instead. Along with researchers at the Swiss Federal Institute of Technology Zurich, they developed an algorithm that can take any solid 3D object and turn it into a top.
To understand the challenge, think of spinning a teapot on a single point. It’s round, sure—but between “here is my handle” and “here is my spout,” it’s unbalanced and won’t stay up.