Veronique Greenwood

When a bird preens its feathers, it uses a little of nature’s own pomade: an oil made by glands just above the tail. This oil helps clean and protect the bird’s plumage but also contains a delicate bouquet of scents.

To other birds — potential mates or would-be rivals — these smells carry many messages, not unlike the birdsongs and fancy feathers that are more obvious to human observers. These scents may signal that a bird would be dangerous to encounter or might be ready to mate, or any number of other cues.

However, new research using dark-eyed juncos, a common North American bird, suggests that these odoriferous messages may not be entirely of the bird’s own making. In a study published last month in the Journal of Experimental Biology, biologists reported that microbes living peacefully on the birds’ oil glands may play an important role in making the scent molecules involved. That implies that the birds’ microbiomes may influence both the smell and the behavior it provokes in other birds.

Birds’ scented messages are the focus of the research of Danielle Whittaker, director of the Beacon Center for the Study of Evolution in Action at Michigan State University and an author of the paper. Some years ago, after she gave a talk, Kevin Theis, a colleague who studied scent-producing bacteria living on hyenas and who is a co-author of the new paper, asked her whether she had ever looked at the birds’ microbes.

“I had never thought about bacteria at all,” said Whittaker. “But all the compounds I was describing were known byproducts of bacterial metabolism.”

Whittaker took samples of bacteria living on the oil glands of 10 captive dark-eyed juncos and then injected the glands with an antibiotic. When she compared the microbes before and after the treatment, the results seemed to show that two groups of bacteria in particular had taken a hit from the treatment. Furthermore, when she compared the scent molecules in the oil before and after the treatment, there were significant differences.

For a follow-up experiment, she and her colleagues grew bacteria from untreated juncos in Petri dishes and checked to see what aroma molecules they were making.

“Every bacterium we looked at produced at least some of” the aromatic molecules, said Whittaker. The microbes living in individual juncos, if they worked together, were capable of making all the scent compounds she had been studying.

It isn’t clear whether the bacteria are the only source of the smell or whether the birds produce some of the molecules as well. But the study opens up the intriguing possibility that birds’ smells may be linked to their microbiomes.

Whittaker has found in other studies that birds tend to have bacteria and odors in common with the individuals they spend time with, suggesting that the microbes move between hosts. There is some evidence that the same is true for humans. A study of roller derby participants found that after a match, skaters’ skin microbiomes were more similar than they had been before.

If birds’ smells are shaped by their bacteria, then perhaps their preferences for mates and for other choices are related to certain populations of microbes as well. Whittaker is planning to study a population of urban juncos to see whether they have their own microbes and version of what’s attractive, as far as smell goes, when compared to their woodland brethren.

In just a handful of decades, these city-living juncos no longer interbreed with their country cousins. Whittaker wonders whether their microbiomes could be contributing to this process.

“I want to see if that is playing a role in the difference between their odors and see if that might be playing a role in why they’re becoming reproductively isolated,” she said. “Are they choosing to mate with birds that have the same smell as them? Is the microbiome helping make that go faster?”

This article originally appeared in

The Bacterial Surprise in This Bird's Smell

(Trilobites)

Rona, who was celebrating her 29th birthday, had planned to meet her family there in a few hours, but she learned that militants had taken control of the building. It was one of many incidents in the upheaval that was tearing at Hungary in the immediate aftermath of World War I and the disintegration of the Austro-Hungarian Empire.

It was also typical of the unsettled world that Rona — a woman who was ethnically Jewish in a male-dominated world plagued by anti-Semitism — had to navigate throughout her career as a chemist researching the strange new science of radioactivity.

Rona moved from lab to lab — often from country to country — to seize opportunities for research. As a result of her work, the world would learn fundamental details of the behavior of atoms and how radioactivity could be used as a clock in studying the Earth’s history, informing the modern practice of geochronology.

The Earth is threaded with radioactive isotopes that decay at a constant rate into other substances, a process that scientists can use to study the planet’s history. For example, the more recent past can be examined by measuring how much carbon-14 in a sample has decayed into nitrogen, with each stage of decay like the ticking of a second hand. For the more distant past, scientists can examine how much potassium-40 has turned into argon-40, or choose another pair that fits their needs. Radiometric dating lets scientists assign dates to objects, like fossils and ancient coral reefs, which reflect the planet’s past climate.

Elizabeth Rona was born March 20, 1890, in Budapest to Ida Mahler and Samuel Rona. Her father was a doctor, and she wanted to become a doctor, too. But her father, fearing the work would be difficult for a woman, encouraged her to study chemistry instead. After earning her Ph.D. at the University of Budapest, she worked as a researcher with the radiochemist Kasimir Fajans at the University of Karlsruhe (now the Karlsruhe Institute of Technology) in Germany.

She returned to Hungary and worked with George von Hevesy, a chemist whose experiments used radioactive versions of elements as tracers to explore chemical reactions. Rona and von Hevesy tracked the diffusion of radioactive tracers in various materials to see how quickly atoms of a substance drifted from one area to another. With that information, it would be possible to calculate an atom’s size, which could then be used to help explain its behavior.

In those early days, radiochemistry was a kind of scavenger hunt to collect and understand these features. Every kernel of information was swiftly fed into new theories and predictions about radioactivity and atoms.

Von Hevesy and Rona’s findings were important for other scientists, but the tracers, for which von Hevesy eventually won the Nobel Prize, turned out to have even broader uses: For decades now, doctors have injected radioactive tracers into patients to aid in diagnosing conditions like cancer and heart disease.

Rona was later invited to work with radiochemist Otto Hahn in Berlin. She arrived at the Kaiser Wilhelm Institute in 1921 to do research alongside scientific giants like Lise Meitner, who along with Hahn would contribute to the discovery of nuclear fission, the reaction at the heart of the atom bomb.

Rona set to work isolating a potential new element called ionium. The substance turned out to be an isotope of the naturally occurring radioactive metal thorium, which had already been well studied. But thorium would play an important role in Rona’s later career.

Trying to escape the hardships of post-World War I Berlin, Rona briefly worked as an industrial chemist at a textile plant in Hungary, where she developed a method to turn flax into a burlap-like material. When Stefan Meyer, the director of the Radium Institute in Vienna, offered her a research job in his lab, she moved again.

Scientists knew that exposing atoms to a radioactive element like radium would trigger reactions, revealing details of their internal structure and physics. But radium was rare and costly, with tiny quantities hoarded and chivvied between nations for experiments. Researchers soon learned that polonium could be used in these experiments instead. Rona was one of those who learned to prepare the polonium, which made her in demand by high-profile labs.

Rona traveled to Paris to work on making concentrated polonium sources alongside Irene Joliot-Curie, Marie Curie’s daughter. Rona’s polonium went on to be used in numerous experiments.

In the years following her Paris sojourn, Rona started to explore the phenomenon of radioactivity in seawater. Each summer, in an island laboratory in Sweden, she measured natural radioactivity in the ocean. She soon realized that there were important differences between the radioactivity of what was floating in the water and what settled on the seabed.

Again, politics interrupted her research. The rise of the Nazis forced her to flee Europe for the United States.

To aid in the war effort, she gave the United States her methods for concentrating polonium, which were used in the project of building an atomic bomb.

She later became a teacher at the Oak Ridge Institute of Nuclear Studies in Oak Ridge, Tennessee, and a professor of oceanography at the University of Miami. She continued her work on seawater, analyzing its uranium content. Uranium levels were constant in oceans across the world, she found. Thorium, however, sinks to the sea floor.

That discovery had important implications: Anything growing in seawater, like a coral reef, will have uranium but no thorium in it — at least at first. Over the course of eons, uranium gradually breaks down into thorium. It happens at such a predictable rate that scientists can deduce the age of an ancient reef from the amount of thorium in it. Furthermore, the fact that thorium builds up on the sea floor can also be used to date deep sea sediment cores.

This set of radioactive clocks, which draw on observations that Rona made over the course of her peripatetic life, have been used around the world for more than 50 years to construct pictures of past tectonic events and measure how sea level has changed.

Rona outlived many of her colleagues, who died prematurely of ailments related to radiation exposure. She was always careful, buying a protective gas mask for herself when her supervisor declined to, and survived at least two lab explosions.

Despite the many dangers of her time — from radiation, revolutions and wars — Rona worked on radioactivity for nearly six decades, contributing to one of the most important chapters of its study.

She died on July 27, 1981. She was 91.

Overlooked No More: Elizabeth Rona, Pioneering Scientist Amid Dangers of War

The phone call for Elizabeth Rona came to the Budapest university where she worked: Don’t go to the theater, the caller warned.

The tiny swimming beetles of the Australian desert live circumscribed lives. Denizens of a series of underground, water-filled chambers, they rarely, if ever, get to the surface. And that raises an important question: How the heck are they breathing?

Other water-dwelling beetles that split their time on the surface capture an air bubble beneath their wings before they dive, which they use like a scuba tank. Or, they have special hairlike structures that let them eke out their own air supply underwater.

Scientists who have taken a close look at these Australian beetles, however, reported Thursday in the Journal of Experimental Biology that the insects use neither of these approaches. Instead, they appear to siphon oxygen directly from the water, breathing, in essence, with their skin.

The scientists have spied on the beetles by peering down boreholes made by mining companies in the soft red rock around their watery habitats.

“You see lots of little creatures zipping about in the water,” said Karl Jones, a graduate student at the University of Adelaide in Australia and an author of the new paper. “We’re able to put small nets down these boreholes, which are only about 35 millimeters in diameter, and catch the animals swimming around in the water.”

After carefully bringing the beetles back to the lab, the researchers put them through a series of tests.

Some of the beetles they looked at under an electron microscope to get a sense of the topography of their outsides. Strictly speaking, beetles don’t have skin. Instead they’re covered in what’s called a cuticle (not the same as the skin layer on your finger), a stiff layer of outer tissue. Some species have structures like hollow hairs on their cuticles that allow them to pull oxygen from the water into their respiratory system. But the three species examined in this study lacked such structures.

However, when the scientists glued the beetles to the end of a wire, submerged them and monitored the oxygen content of the surrounding water, they observed something curious. The closer the sensor got to the beetle, the lower the oxygen reading. This suggested that the beetles were somehow drawing the oxygen out of the water immediately around them.

“It’s going right through the cuticle, either right into the respiratory system or directly into the tissue,” Jones said.

This strategy has been seen before in insect larvae that live underwater, but not yet in mature beetles.

The researchers found that these beetles have markedly thin cuticles compared with their surface-dwelling brethren, which would make it easier for oxygen to diffuse through it.

They are also very small creatures — ranging in size from less than 1 millimeter to just under 5. That fits with the idea that they might rely on this not-terribly-efficient way to absorb oxygen. It would not work for a bigger insect, but for something smaller than a child’s thumbnail, it may be all they need to survive in their watery underground worlds.

This article originally appeared in <a href="https://www.nytimes.com/2019/04/09/science/underwater-beetles-breathe-skin.html" id="732c96c4-656a-3ee6-a61d-c23ad1194059">The New York Times</a>.

How Beetles That Live Underwater Breathe Without a Scuba Tank

The sun bears were making faces at each other. And that was a bit of a surprise.

Comparative psychologists have been studying the facial expressions of primates like orangutans and gorillas for years. They have evolved in complex societies and thus need to be able to convey their joy, anger and other emotions to their companions. But nobody had thought to look at creatures like sun bears, who live mostly solitary lives.

Marina Davila-Ross, a primatologist at the University of Portsmouth in England, and her colleagues learned that a handful of the Southeast Asian bears, which primarily live alone in the wild, were in a rehabilitation center near the orangutan center in Malaysia where Davila-Ross was doing research.

Curious about whether facial communication was more common in the animal kingdom that people thought, they deployed cameras to capture hours of footage of the bears interacting with each other. In a study published Thursday in Scientific Reports, they say that sun bears do use facial expressions to communicate, suggesting that the capacity to do so may be widespread, and that social creatures do not have a monopoly on expressing themselves this way.

Sun bears are exceedingly solitary. A female’s one or two cubs will live with her for about two years, and then set off for lives on their own. Adults seem to rarely meet, except for mating. At the center, bears that cannot be released back into the wild live in enclosures in groups of five or six. For the bears, it was an unnatural setup — but it was perfect for the scientists.

In their footage of 22 bears going about their daily lives, the scientists zeroed in on moments when the animals were playing, batting at each other and grappling good-humoredly. They watched for moments where the playing bears were looking into each other’s faces, and then they looked for certain facial expressions, like opening one’s mouth wide and showing teeth.

They found that very often when one bear made such an expression, the other bear would make it a second later. This happened frequently, and so precisely — they were making not just any expression, but very much the one on their playmate’s face — that the scientists believe they were mimicking each other.

“It’s not just an emotional outburst,” said Davila-Ross, meaning that the bears were not just showing pleasure generally. They appear to be looking to communicate with each other.

What are the sun bears saying to each other? “This is not all that clear yet, but there are some indications that it may help coordinate social play behaviors and be linked to longer play bouts,” Davila-Ross said. “As such, it may help to strengthen social bonds between the interacting individuals.”

The researchers hope that the study of other solitary mammals, like leopards, living together in zoos and rehabilitation centers will reveal the true breadth of this kind of behavior.

Davila-Ross and her colleagues are now using their video footage to learn about the bears as individuals and to what extent they each have their own way of behaving. Understanding how sun bears behave may help determine which are good candidates to be returned to the wild, she said.

Outside the walls of the center, sun bears’ numbers are dwindling. Their home forests are being destroyed by human encroachment, and they are exploited for traditional Chinese medicine. They are listed as “vulnerable,” even as scientists work to learn more about the bears’ inner lives.

This article originally appeared in <a href="https://www.nytimes.com/2019/03/22/science/sun-bears-faces-mimicry.html" id="59adfe21-079f-3b9b-a607-fcaf9b4a1c7e">The New York Times</a>.

Sun Bears Seem to Communicate Via Face Time

Squid are chameleons of the ocean, shifting effortlessly from hue to hue as they cross sand, coral and grass. Scientists have long studied the peculiar structures in their skin that interact with light, trying to understand how the animals change color so swiftly and with such precision.

Now, a paper published last week in Nature Communications suggests that their chromatophores, previously thought to be mainly pockets of pigment embedded in their skin, are also equipped with tiny reflectors made of proteins. These reflectors aid the squid to produce such a wide array of colors, including iridescent greens and blues, within a second of passing in front of a new background. The research reveals that by using tricks found in other parts of the animal kingdom — like shimmering butterflies and peacocks — squid are able to combine multiple approaches to produce their vivid camouflage.

The researchers studied Doryteuthis pealeii, or the longfin squid, which is found in the North Atlantic Ocean and might turn up on your plate when you order calamari.

Its chromatophores contain individual sacs of yellow, red or brown pigment. Each one is also ringed with small muscles that allow the animal to clench shut or open wide each chromatophore. That means that in front of brown sea grass, for example, red and yellow chromatophores might cinch closed, allowing the brown pigments to show.

But what is the source of all those vivid blues and greens that squid are known to display? Researchers had long imagined that the layer below the chromatophores in the squid’s skin might be responsible for those pyrotechnic shimmers. That underlayer is essentially an enormous reflector, made of cells that make a protein called reflectin.

However, that layer responds to changes too slowly to be the sole source of those colors, said Leila Deravi, a professor of chemistry at Northeastern University and an author of the new paper.

In search of answers, she and her collaborators at the Woods Hole Oceanographic Institution and elsewhere put squid skin under the microscope and saw something reflective on the surface of the chromatophores. As they moved a beam of light to shine at different angles off the skin, the round blobs of yellow, red and brown pigment lit up like Christmas trees.

“We saw a really bright, metallic-y kind of color associated with the chromatophores,” said Deravi. “And at different angles we could see blue-greens come out, we could see just the whole spectrum of color emerge.”

Analyzing the proteins that the chromatophore cells were making, the team realized that reflectin was among them, and they confirmed with further lab work that it was distributed around the surface of the chromatophores.

Light strikes arrays of reflectin, bounces around and refracts out, producing colors. The same kind of interaction, called structural color, produces the blue of a morpho butterfly’s wings, a peacock’s tail father or a blue human eye.

Pigments, by contrast, like the one behind brown eyes, are small molecules that simply absorb some colors of light and release others. These are fundamentally different ways of making color. But squid have the benefit of both.

The squid control the movement of the reflectin that is on the outside of the chromatophores with the same movements that control the opening and closing of the structure’s mouth, manipulating both kinds of color simultaneously. With this intimate connection between the two, “these cephalopods have evolved a way to help them become one of the fastest camouflaging species on the planet,” Deravi said.

The shimmering, shifting surface of the squid’s skin may someday provide insights for new materials that use the same tricks. But how exactly the squid matches its perception of its environment to its appearance using the precise manipulation of thousands of structures all over its skin is still a subject of much research.

“We were always continuously surprised by these animals. As soon as you think you kind of understand how they work, you find something else,” Deravi said.

This article originally appeared in <a href="https://www.nytimes.com/2019/03/07/science/squid-camouflage-colors.html" id="c272be40-4e8f-31b5-a253-c2e9d34b7f24">The New York Times</a>.

Squid Share a Colorful Trick With Peacocks

For thousands of years, penguins have darted through the waters of the southern oceans, chasing fish and surfacing to nest on islands and landmasses sprinkled from the Galápagos to the Antarctic. Today there are around 20 penguin species, ranging from the playful Adelie to the stately Emperor. But there once were other penguins, including a previously unknown subspecies of dwarf yellow-eyed penguin in New Zealand.

You won’t be seeing it any time soon. It’s extinct, apparently wiped out by humans hundreds of years ago.

“We suspect that these Megadyptes penguins were on their way to becoming a full new species,” said Theresa Cole, a graduate student at University of Otago in New Zealand and co-author of a paper about this bird and another newly discovered extinct subspecies of crested penguin. “But they just didn’t get a chance, because people ate them.”

Cole and her colleagues sequenced DNA from many penguin species and built a family tree of the waddling birds living and dead. The resulting research, published Tuesday in the journal Molecular and Biological Evolution, led to the discovery of these two subspecies. It also suggests that the same island environments that resulted in such diversity in the penguin family can also be linked to doom for some as they eventually came into contact with hungry human settlers.

With their family tree, Cole and her fellow researchers set out to understand when it was that these birds started to diverge from each other. The researchers linked the tree to the dates assigned to fossilized penguins, and from that, they were able to deduce the rough timing of the penguins’ radiation into different species over millions of years.

That revealed something intriguing. Many penguins are native to specific volcanic islands, which arose relatively quickly from solidified lava. Often, the researchers found, the appearance of new penguin species was closely tied in time to the appearance of those penguins’ native islands. In other words, before the islands formed, the species that call them home today did not exist. Rather, these species came into being when penguins from elsewhere popped out of the sea near the new patches of earth, began to make a new life for themselves, and slowly evolved into a new species.

The dwarf yellow-eyed penguin and the new crested penguin were natives of the Chatham Islands in southern New Zealand. The dwarf penguin was genetically very similar to the yellow-eyed penguins that currently roam New Zealand’s mainland. But the little creatures were even smaller than the yellow-eyed penguins, which are only a couple of feet tall.

The bones of both penguins have been found in trash heaps that date back to when humans arrived in the Chatham Islands. Circumstances suggest that the animals were cooked and eaten, and they soon went extinct.

They would not have been the first island birds to suffer from the arrival of ravenous bipeds, and sadly, they were not the last. In recent years, penguin numbers around the world have plummeted. One recent study projected that by 2060 the yellow-eyed penguins still living in New Zealand may join their dwarf relatives in extinction, unless an effort is made to preserve them.

“Throughout the southern hemisphere, in particular in the Pacific, penguin populations are declining,” said Cole. “Pretty much all of the penguins that are endemic to New Zealand are faced with various threats including fishing, and pollution, and warming sea surface temperatures, and competition with humans, dogs eating penguins, habitat fragmentation. Even though humans aren’t eating them anymore, there are other impacts that will keep driving them to extinction.”

This article originally appeared in <a href="https://www.nytimes.com/2019/02/08/science/penguins-islands-extinctions.html" id="bf5386a5-f635-3691-adc4-e1368b7ebdb5">The New York Times</a>.

Islands Helped Penguins Evolve. Then Hungry Humans Showed Up.

Now, in a study published Tuesday in Nature Communications, researchers curious about the genetic underpinnings of chronotype — whether you are a morning person, a night owl or somewhere in between — looked at about 700,000 people’s genomes. They identified 351 variations that may be connected to when people go to bed. While these variants are just the beginning of exploring the differences in chronotypes, the study goes on to suggest tantalizing links between chronotype and mental health.

The researchers drew on data from 23andMe, the genetic testing company, and the UK Biobank, which tracks hundreds of thousands of volunteer subjects in Britain, about 85,000 of whom wear activity monitors that record their movements.

Those data were key, said Michael Weedon, a bioinformaticist at University of Exeter in England and an author of the new paper; earlier studies had relied only on people’s subjective opinions of whether they were morning people. Using the activity monitors, however, the team was able to confirm that self-reported morning people did go to sleep earlier — and people with the most morning-linked gene variants went to bed 25 minutes earlier than people with the fewest. Morning people did not sleep longer or better than night people; all that differed was the time that they went to sleep.

The genes flagged in the study play a wide variety of roles in the body.

Many seem to play a role in brain tissues, and others are already known to be central to the body’s circadian rhythm. A few were active mainly in the retina, and the people who possessed an uncommon version of one of these genes had an increased chance of being night owls, said Samuel Jones, a researcher at the University of Exeter and the study’s lead author. That could imply a potential a connection between how the eye responds to sunlight and when a person sleeps.

Another gene was involved in the body’s processing of caffeine and nicotine, two of our species’ favorite stimulants. Continued study of these and the other genes could provide leads for future work on the biology of sleep timing.

“The most interesting ones are the ones where we don’t know what it is,” Weedon said.

When the researchers crunched the numbers on chronotype’s connection to mental health, they also found that self-identified morning people reported a higher level of general well-being. People in this group also were less likely to report having depression or schizophrenia, in line with epidemiological studies suggesting that evening people struggle with mental health.

The researchers wonder whether having a lifestyle that aligns with one’s chronotype may be more important in mental and physical health than whether you are merely a morning or night person. In future work, they are hoping to see whether morning people who are required to stay up late for their jobs or other commitments — perhaps similar to night owls who must rise early for 9-to-5 jobs — show higher levels of mental disorders than their well-aligned counterparts.

“Perhaps evening people are constantly fighting their natural clock, which might have unintended consequences farther down the line,” Jones said.

This article originally appeared in <a href="https://www.nytimes.com/2019/01/30/health/morning-person-genes.html" id="2f1ac642-becb-3ffa-a65b-6342b88bf6d5">The New York Times</a>.

Early to bed and early to rise is a maxim that’s easy to follow for some people and devilishly hard for others.

Searching for the Genetic Underpinnings of Morning People and Night Owls

Look closely up in the trees of a shade-grown cacao plantation in eastern Costa Rica, and you’ll see an array of small furry faces peering back at you. Those are three-toed sloths that make their homes there, clambering ever so slowly into the upper branches to bask in the morning sun. You might also spot them munching on leaves from the guarumo tree, which shades the cacao plants.

Scientists have long known that this tree is important to the diets of sloths. Its foliage is highly nutritious, available all year and easy for the creatures to digest. But in a new study published Tuesday in Proceedings of the Royal Academy B, researchers report that a population of sloths with more guarumo trees in their cacao plantation habitat had more babies and were more likely to survive.

Their findings suggest that the tree’s presence can help ensure the health of sloth populations even in environments that have already been disturbed by humans, like farms. It also shows how animals that have a specialized ecological niche, while traditionally thought of as vulnerable, can persist in changed circumstances as long as the resource that they depend on is available.

For almost 10 years, Jonathan Pauli and M. Zachariah Peery, professors at the University of Wisconsin, and their colleagues have tracked a group of sloths in Costa Rica. The animals are equipped with radio collars that transmit their location five or six times a month, so the team knows where each sloth’s usual territory is. The team has also taken DNA samples and figured out the sloths’ family tree, so they can tell which individuals are having the most babies.

When Mario Garcés-Restrepo, the paper’s lead author, grew interested in whether what the animals were eating could be linked to their reproductive success, the groundwork to answer the question was already in place.

Three-toed sloths are not known for their dietary flexibility — they tend to rely on a small handful of plants. But while they usually live in tropical rain forests, sloths can manage surprisingly well in other environments as long as the right variety of trees and nearby streams are available.

Garces-Restrepo mapped the numbers of various trees in about 40 sloths’ favored territories and checked to see whether there was a correlation between the density of a given tree species and an animal’s number of offspring and survival over the course of the study.

While the survival of juvenile sloths was not linked to guarumo, the trees appeared to be important for the group’s adults. The five adults who died over the course of the study had markedly lower numbers of guarumo in their area than those that survived. At the same time, both male and female adults with more guarumo available to them had more offspring, the males in particular. That may be not only because of the nutrition the tree offers, but the visibility, as lanky guarumo trees have open structures with plenty of places to see and be seen.

“Sloths are often seen sunbathing in the mornings,” Pauli explained, and if they are attracting mates by calling to them or making themselves visible, he said, “being in open trees might actually enhance those reproductive opportunities.”

This improved understanding of what the sloths need to thrive could be important in this area and others where they live. In northeastern Costa Rica where the study was completed, the area around the cacao plantation is shifting. “The landscape is changing,” said Pauli, with more fields of pineapple being planted, which grows only in open, unforested spaces. There may be fewer places for sloths there in the future.

This article originally appeared in <a href="https://www.nytimes.com/2019/01/22/science/sloths-diet-trees.html" id="fdaf7844-2190-34eb-a98a-b829a93b2e38">The New York Times</a>.

Where Sloths Find These Branches, Their Family Trees Expand

Reindeer cannot fly around the world helping distribute gifts to all the good boys and girls in a single night — at least, as far as science can tell. But they are capable of other impressive feats.

On the Arctic island of Svalbard, Norway, the shaggy white creatures eat almost nonstop to store up fat during the summer months of the midnight sun. Then, during the long winter of total darkness and little food, they live mostly off energy reserves.

“They are normal mammals only about three months a year,” said Walter Arnold, a professor at the University of Veterinary Medicine in Vienna who studies animals’ adaptations to cold.

The rest of the time, extreme conditions demand extreme behaviors. For instance, some research suggested that Svalbard reindeer lacked standard circadian rhythms, leading to speculation that their body clocks had been lost over evolutionary time.

But Arnold and colleagues recently reported in a small study in Scientific Reports that they do have a circadian cycle. Like most other things about them, it is a bit peculiar. The variations are sometimes so slight that observing them required years of monitoring with sensitive sensors that sit in the reindeers’ stomachs.

Arnold and his collaborators used pill-shaped metal capsules containing the sensors. Once swallowed, the capsules stay harmlessly in the animal’s stomach as long as it lives, transmitting information about temperature, movement and heart rate. When the researchers looked at roughly two years of data from four reindeer, they saw interesting patterns.

“From our physiological data, it was clear from the first glance, the first analysis, that in body temperature there was clearly a diurnal rhythm,” Arnold said.

Further analysis showed rhythms in other measurements, too.

In the months leading up to summer, there is sun but not yet much greenery. Then, the cycles of the reindeers’ circadian clock have their highest highs and lowest lows, perhaps driving the animals to forage what is available during the day and prepare for what’s ahead.

When summer arrives, the reindeer’s circadian cycles are weak and perhaps easier to ignore. During that season, reindeer must stay awake at all hours to eat as much as possible.

“They just don’t listen to the clock anymore. They are shift workers during that time,” Arnold said.

Staying up late may be key to survival: If they slept more during the precious period when they are actually able to graze, they might not be able to make it through winter.

The intense activity of summer, abetted by their peculiar clocks, is eventually replaced by a winter of striking somnolence. They do not hibernate, but they get very close.

“I would call them walking hibernators,” Arnold said.

The study’s measurements show that in winter, the reindeers’ metabolic rate is suppressed to just a third of its summer high — not a state that would lend itself to taking off from rooftops.

Humans who ignore their clocks, far from thriving, have higher rates of some cancers, heart disease and other health problems. How do reindeer manage?

“We have no idea how this works,” said Arnold, noting that there are still many mysteries in the lifestyles of animals in the planet’s most extreme habitats.

This article originally appeared in <a href="https://www.nytimes.com/2018/12/24/science/reindeer-body-clock.html" id="10982596-c800-3b97-a96b-e08367fee2db">The New York Times</a>.

Perhaps Santa Had to Shout to His Eight Reindeer Because They Fell Asleep

The mollusk, unearthed from the bottom of a river in the Philippines, was introduced this week by an international group of scientists in Proceedings of the Royal Society B. It is a shipworm, a group of burrowing animals related to clams, but so different from known examples that it is both a new species and genus.

Shipworms are usually known for their habit of eating wood. It’s right there in the name: They use their shells, attached to one end of their bodies, as chewing devices to burrow into and consume ship bottoms, docks and any other submerged wood. The behavior has made them the plague of mariners past and present, and in recent times, they have even sampled the delights of at least one New York City pier.

Wood-eating shipworms fascinate scientists because they digest pulverized wood with the help of symbiotic bacteria that live in their gills. The bacteria manufacture an array of enzymes and other substances, and studying them and finding new shipworms may prove helpful in the search for new antibiotics, a subject of interest to the scientists behind the new paper.

They first heard reports of a mysterious shipworm in the Abatan River on Bohol Island some years ago, from an expedition organized by the French National Museum of Natural History. Reuben Shipway and Daniel Distel of Northeastern University, members of the Philippine Mollusk Symbiont International Collaborative Biodiversity Group, went in search of the creatures with snorkeling masks and chisels in tow.

A local resident suggested they check the bottom of the river; underwater, they spotted huge chunks of sandstone peppered with holes. Protruding from some of the rocks were the twin flags of shipworm siphons, organs that the creatures use to excrete.

“That was when we knew we’d struck shipworm gold,” said Shipway.

The researchers extracted the translucent white creatures from their burrows and performed various tests and dissections. That was when they learned more details about L. abatanica’s intriguing lifestyle.

The cecum, a large organ used in digesting wood that is common across shipworms, was missing in the new species. The shipworms’ guts, however, were full of fragments of stone, which chemical analysis showed to be the same stone that the animals were living in. What came out was stone, too.

“We had a few animals in a makeshift aquarium,” said Shipway, “and you could put the animals in the aquarium and basically watch them excreting fine particles of sand out of their siphon.”

Exactly what the shipworms are getting from the stone is not yet clear. One possibility, the researchers speculate, is that the granules could be helping them grind up plankton and other creatures floating in the water, much the way gizzard stones help birds break down food they’ve swallowed whole.

But it may be that the worms are able to extract nutrients from the stone in a way not yet understood. The gills of the stone-eating shipworms are much larger than other shipworms’, suggesting that the organ’s tiny inhabitants may be particularly important to the creature’s survival. The team is now working on sequencing the genomes of L. abatanica’s symbionts to identify them and get a glimpse of how their metabolism works.

“It’s already looking very, very interesting,” said Distel. “What we can say is that the bacteria we find in the gills are not related to the bacteria we’ve found in any other shipworm to date.”

This article originally appeared in <a href="https://www.nytimes.com/2019/06/18/science/shipworm-rocks-sand.html" id="c16f99f5-e0c3-3346-a23a-4d444b3eb772">The New York Times</a>.

This creature eats stone, sand comes out the other end

Lithoredo abatanica is an organism with an unusual appetite: This creature eats stone. And when it excretes, what comes out is sand, the leftovers of a still-mysterious digestion process.

<h1>(Trilobites): It is a truth universally acknowledged — or at least, much discussed on social media — that a woman who works in an office is in want of a sweater.</h1>

Office air conditioning is often set at a temperature that women find chilly; the resulting water-cooler debate has been called the “battle of the thermostat.” One study even suggested that because women have slower metabolic rates, the formula used to set temperatures in workplaces, which was developed decades ago based on the comfort of men, may overestimate women’s body heat production by 35%.

A question that hasn’t been asked much, however, is whether temperature affects the productivity of men and women differently. In a study published Wednesday in the journal PLOS One, researchers reported that at lower temperatures, men scored higher than women on verbal and math tests. But as a room grew warmer, women’s scores rose significantly. The findings require further confirmation under an assortment of conditions. But they add to a scientific rethinking of the spaces where we work and study, which sometimes have been devised with a limited set of physical requirements in mind.

The researchers asked more than 500 college students to take tests for an hour in rooms with temperatures between 61 and 90 degrees Fahrenheit. The students performed as many simple math problems (without the help of a calculator) as possible, and rearranged a set of letters into as many words as they could, within a time limit. They also were asked to solve a series of tricky logic problems.

The temperature had no effect on the scores when they were considered as a group. But when the researchers split the data between male and female subjects, a clear pattern emerged. Scores on the logic problems did not vary as temperatures changed, but the math and verbal test scores did.

“If temperatures are cold, men are much better than women,” said Agne Kajackaite, a behavioral economics researcher at WZB Berlin Social Science Center in Germany and an author of the study. “So there is this gender gap.”

She added, “But then when temperature increases, the gender gap disappears” on the math test, and women outpace men on the verbal test.

For each increase of 1.8 degrees, women’s math scores rose by 1.76%. That difference might sound small, but it added up.

“When the temperature was below 70 Fahrenheit, females solved, on average, 8.31 math tasks correctly,” Kajackaite said. “And when the temperature was above 80 Fahrenheit, females solved 10.56 tasks.”

She added, “That is, female performance increased by 27%.”

Do the findings mean there is some ideal temperature at which male and female abilities are more or less even? That’s a big leap to take from one study that exposed people to these temperatures for just an hour, Kajackaite said.

“You don’t have much time to get annoyed,” she said.

We are in our workplaces or classrooms for longer periods than that, and the outcomes might be different over the course of several hours or a full day, a question for future studies to address.

The researchers did notice an interesting detail in the math results. As the temperature rose, women’s scores went up, not just because their percentage improved but because they were ramping up the number of problems they took on. Why might that be?

“Females feel better when it’s warmer, so they can exert more effort,” Kajackaite speculated. “On a good day, you will try more. On a bad day, you will try less.”

This article originally appeared in <a id="636ce41c-6070-4eb1-ac90-d96576b837ec" href="https://www.nytimes.com/2019/05/22/health/women-temperature-tests.html">The New York Times</a>.

In warmer rooms, women were better test takers

Office air conditioning is often set at a temperature that women find chilly; the resulting water-cooler debate has been called the “battle of the thermostat.”

In a paper published last week in the Journal of Agricultural and Food Chemistry, the researchers behind this endeavor reveal that dark chocolate’s aroma comes down to 25 molecules, in just the right concentrations — some of which you might find rather disgusting if you sniffed them on their own.

The sensory panel was part of a study on chocolates with cacao contents from 90 to 99%, which are growing more popular, said Michael Granvogl, a chemist at the University of Hohenheim in Germany who wrote the paper with Carolin Seyfried of the Technical University of Munich. While chocolate flavors — which, like all flavors, are a combination of taste and smell working together — have been studied for decades, this was one of the first times chocolate of such high cacao concentrations has come under the microscope. Or rather, perhaps, the sniff-o-scope.

Fed through a battery of analytical machines, the chocolates yielded 77 compounds that could contribute to the chocolates’ aroma. Some were at levels too low to be detected by the human nose. But around 30 others made the sensory cut.

If you looked at a list of what each molecule smells like individually, you might notice something surprising. For instance, acetic acid, the odor molecule present in the highest levels in the chocolates, smells like vinegar by itself. And 3-methylbutanoic acid has a rancid, sweaty stench on its own. Then there’s dimethyl trisulfide, which smells like cabbage.

But these and other compounds, at very particular concentrations, work together to play the elaborate pipe organ that is our olfactory system. Together they attach to receptors in the nose and the back of the mouth to play a specific set of keys, creating a neural chord that says not “cabbage” or “sweat” or “vinegar,” nor even a mixture of these, but “chocolate.” Specifically, in this case, “very dark chocolate.”

Working backward to assemble the chord, the scientists were able to re-create the scent to the satisfaction of the trained sniffers using just 25 of those molecules.

The goal is not necessarily to create artificial versions of familiar food aromas. Understanding what is behind a smell can help make it clear what has gone wrong when a food product has an off-taste or scent.

The study also suggests that the wonderfully diverse world of flavor and aroma may, thanks to our pipe-organ sense of smell, be generated by a relatively small number of molecules working in concert. In other work, Granvogl’s colleagues have found that with around 226 molecules, they can make mixtures that capture the flavors of about 227 different types of food, from meats, fish and cheeses to chocolate.

“Butter is very easy — you only need four components to mimic butter flavor,” he said.

It is the concentrations of the molecules, not just their identities, that count, he and his colleagues have found. The exact same molecules make up the flavor of peanuts and hazelnuts, for instance.

“If you mix it in different concentrations, you end up on the one side with a hazelnut flavor and on the other side, a peanut flavor,” Granvogl said.

This article originally appeared in <a id="7a53e396-b64d-4062-b905-827585022b01" href="https://www.nytimes.com/2019/05/15/science/dark-chocolate-smell.html">The New York Times</a>.

Alone, they stink, together they create dark chocolate's alluring aroma

(Trilobites): If there was ever a science experiment you’d want to participate in, it might be this one: sitting in a booth and inhaling the tangy, intense aromas of dark chocolates. But not just anyone gets to join this research. The people doing the sniffing were trained to detect subtle differences in scent, helping chemists uncover just which odor molecules are behind the distinctive smell of these rich treats.

<h1>Squid are chameleons of the ocean, shifting effortlessly from hue to hue as they cross sand, coral and grass. Scientists have long studied the peculiar structures in their skin that interact with light, trying to understand how the animals change color so swiftly and with such precision.</h1>

In search of answers, she and her collaborators at the Marine Biological Laboratory in Woods Hole, Massachusetts, and elsewhere put squid skin under the microscope and saw something reflective on the surface of the chromatophores. As they moved a beam of light to shine at different angles off the skin, the round blobs of yellow, red and brown pigment lit up like Christmas trees.

This article originally appeared in <a id="90b64272-3bb0-44c1-91f8-185e20b86293" href="https://www.nytimes.com/2019/03/07/science/squid-camouflage-colors.html">The New York Times</a>.

Squid share a colorful trick with peacocks

The researchers studied Doryteuthis pealeii, or the longfin squid, which is found in the North Atlantic Ocean and might turn up on your plate when you order calamari.

<h1>Sleep — that absurd, amazing habit of losing consciousness for hours on end — is so universal across the animal kingdom that we usually assume it is essential to survival. Now, however, scientists who repeatedly disturbed the sleep of more than a thousand fruit flies are reporting that less slumber may be necessary for sustaining life than previously thought, at least in one species.</h1>

A handful of studies involving dogs and cockroaches going back to the late 19th century suggest that being deprived of sleep can result in a shortened life span. But the methods behind some of these studies can make it difficult to say whether the test subjects were harmed by sleep deprivation itself, or by the stress of the treatment they were given — such as being shaken constantly.

The new study took a milder approach, in hope of seeing the true effects of sleep deprivation. The automated system the researchers developed for monitoring the flies kept track of their movements with cameras, scoring any extended period without movement as sleep. When they were not being awakened repeatedly, the males slept about 10 hours a day, females about five on average.

To keep the flies awake, the researchers equipped the system with tiny motors that would gently tip the flies any time they went still for at least 20 seconds. With this method, researchers deprived flies of rest over the course of their entire lifetimes, tipping them hundreds of times a day such that if they were snoozing during those periods of stillness, they might have been able to sleep around 2.5 hours a day on average.

“When the results came from that experiment, it was very surprising,” said Giorgio Gilestro, a professor at Imperial College London who is a co-author of the study, which was published Wednesday in Science Advances.

While female flies in the experiment died about 10 days sooner than other flies, male flies had completely normal life spans of about 50 days. Gilestro suggests that perhaps whatever sleep is doing in the way of essential maintenance can happen in a very, very short period of time, such that little sleep is required to keep an organism alive.

The study has limitations. It looked at only a single strain of fruit fly, said Dragana Rogulja, a professor at Harvard University who studies sleep using fruit flies. “In principle, I think it would be have been awesome to test multiple strains,” she said, to understand whether other flies, some of which can live much longer, respond similarly.

Additionally, not everyone agrees that the scientists have succeeded in accurately recording when the flies are awake or asleep. Some periods in which flies made tiny movements were scored as waking time, for instance.

A handful of studies involving dogs and cockroaches going back to the late 19th century suggest that being deprived of sleep can result in a shortened life span.