Coral reefs provide shelter and protection , including crabs, moray eels, octopus and fish. But these cozy homes are currently under threat for many reasons, such as rising sea temperatures and ocean acidification.

Researchers are trying to understand how groups of fish communicate with each other within a coral reef, and how the health of the reef affects that communication.

This fall , a șÚÁÏÀÏËŸ»ú doctoral student in the biology department, and UW research scientist are traveling to the on Magoodhoo, Maldives, to gather live footage of interactions. This fish is a common schooling species on Maldivian reefs. UW News asked Milan a few questions about the trip for the occasional series “In the Field,” which highlights UW field research efforts.Ìę

Tell us about your project.

Jj Milan: I’m studying how fish in schools can accurately communicate the difference between a real threat and a harmless false alarm. And then, once a threat is gone, I want to understand how they coordinate the return to normal behavior.

What will you be doing on this trip?

JM: I’ll be using synchronized cameras and automated tracking to record how threat responses spread through a school. We will be scuba diving to place GoPro cameras and tablets around specific coral heads. We won’t be diving very deep because we need sufficient natural lighting for our video recordings. Our local contacts at the MaRHE Center have confirmed that the surrounding reef is shallow with abundant marine life.

I’m also hoping to collaborate with locals to get more insights into typical fish behavior and predator activity in this area.

What do you hope to learn?

JM: I hope to be able to reconstruct how threat responses move through a school of fish in real time, from the first fish that reacts to how the group settles back into normal behavior. I’ll also reconstruct the three-dimensional structure of the coral to understand if the complexity of the structure changes how quick and how coordinated that response is.

What’s something you really enjoy about doing this field work — especially something that might not occur to most people?

JM: I enjoy how this work brings together my love of ocean life, my diving hobby and my passion for research all in one. I have been diving since 2019 and I am excited because this will be my first time diving in warm water conditions.

More generally, is there anything you find surprising or enlightening about doing field work?

JM: I’m surprised at how many possibilities and opportunities for collaboration arise just during the planning process through connecting with other researchers and resources. I hope to build on these connections in the future.Ìę

For more information, contact Milan at jdmilan@uw.edu.

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Birds evolved from dinosaurs. They share a common ancestor and physical traits — some dinosaurs even had feathers. But while these dinosaurs are thought to have had “fuzzy” or “downy” feathers, ancient birds were more likely to have had feathers that look similar to the birds of today.

A șÚÁÏÀÏËŸ»ú-led research team has discovered the best-preserved fossil feathers from the — in a fossilized dinosaur poop, also known as a “coprolite.” Some of these feathers have features that look like modern birds’ feathers. In in Current Biology, the team describes this finding and how it can help researchers better understand why and how some birds survived the that killed 75% of life on the planet.

The team discovered the feathers in 2016 at a research site in eastern Montana in the badland exposures of the geological formation called the .

“I was crawling up a rocky outcrop collecting fish fossils when I came across a dark, reddish-brown nodule about half the size of a golf ball,” said co-author , a UW research scientist in the biology department and the Hell Creek Project collections manager at the Burke Museum. “I picked it up and scanned its surface through my hand lens, and that’s when I couldn’t believe what I was seeing: a tiny fossil feather. I was cautiously optimistic about its discovery, because feathers had not yet been found in the Hell Creek Formation, even after more than 100 years of prospecting.”

Back in the lab, the researchers examined the specimen’s mineral composition and took CT scans of it — essentially, thousands of X-rays that are digitally stacked to reveal the contents of an object.

“Every hour processing the data revealed another feather, another scale, another bone — in stunning 3D,” said co-author , a paleontologist at the Carter County Museum.

The coprolite contained multiple feathers, tiny fish scales from a gar and leg bones from a , an extinct group of birds that are ecologically similar to loons. The researchers reasoned that the feathers must have also come from this same bird. These are the first hesperornithiform feathers ever found.

The hesperornithiforms are close cousins of the birds that survived the mass extinction and still live today. Some scientists have hypothesized that the birds that survived did so because they lived near water, and something about this habitat helped buffer them from the effects of the mass extinction. But the hesperornithiforms also lived by water, and they went extinct.

“We think the types of feathers that these birds had, and/or the way they molted those feathers, may have been one of the underlying causes of the selectivity of the end-Cretaceous mass extinction — essentially, why some birds died out and why others survived,” said lead author , associate curator of fossil reptiles at the Field Museum. “Some of these diving birds’ feathers seem to have been modern-looking and waterproof, but they also had some smaller fuzzy, primitive body feathers that we associate with dinosaurs.”

If the feathers on hesperornithiforms and other extinct bird species weren’t as good at keeping their bodies warm, the researchers hypothesize, maybe that’s why they weren’t able to survive the extinction event.

“It’s such a beautiful, well-preserved feather, from such an unexpected source, and it’s exciting that it could help us answer this huge question in paleontology,” O’Connor said. “I usually work with fossils that are preserved in big stone slabs, and the entire skeleton and even the soft tissue is preserved — they make it easy for me. But with this project, we just had this coprolite — and its contents — to go off of, and it made me feel like a detective, piecing together all these little clues. And since no one has studied feathers in coprolites before, this opens up a whole new avenue for investigation. We only knew to look at this one because of how it happened to be split open, with the feather exposed — it was literally a lucky break. I hope more scientists start CT scanning coprolites and taking a closer look at them to see what might be inside.”

, UW doctoral student in biology; , the Hell Creek Project Fossil Preparator at the Burke Museum of Natural History; at the University of Colorado, Boulder; at the Field Museum and the University of Chicago; Christian Cooper at the Field Museum; at the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences; at the University of Alabama; at the Natural History Museum of Los Angeles County; at the University of Southern California; and at the Natural History Museum of Los Angeles County are also co-authors on this paper. This research was funded by donations to the Hell Creek Project.

For more information, contact Wilson Mantilla at gpwilson@uw.edu and DeMar at ddemar@uw.edu.

Adapted from .

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A city’s sewers say a lot about its residents. Sick people often shed pathogens in their waste, adding traceable amounts of bacteria and viruses into wastewater. Testing that wastewater offers a simple, low-cost way to monitor the spread of disease — a practice that began with polio in the 1940s and became more widespread during the COVID-19 pandemic. Today, tests for a variety of common and emerging viruses.

American public health agencies don’t routinely test wastewater for sexually transmitted infections, but new research led by the șÚÁÏÀÏËŸ»ú and the Washington State Department of Health found that such methods could be used to effectively identify Chlamydia trachomatis, the bacteria that causes chlamydia.

The study, , could help public health agencies better identify and respond to increased spread of chlamydia and other STIs, which are The researchers specifically explored wastewater’s potential as a community monitoring tool, and not as a way to identify cases or trace pathogens back to individual people or locations.

“STIs are known for being underreported because of a lot of factors, especially stigma and the prevalence of asymptomatic cases,” said co-lead author , assistant professor of environmental and occupational health sciences and of civil and environmental engineering at the UW. “Wastewater is cool because it’s population level. You don’t need people to go to the doctor and seek out treatment to know that there are people in a community shedding specific pathogens.”

Working in collaboration with local health jurisdictions, researchers collected frequent samples from influent wastewater at five wastewater treatment plants across Washington state and six neighborhood-level sewer sites near Seattle. Collection sites ranged from a large, high-population urban area to a rural treatment plant serving fewer than 5,000 people. Researchers masked the specific names and locations of sample locations to protect the privacy of people and communities.

Researchers tested wastewater samples for the pathogens that cause three common STIs: chlamydia, syphilis and gonorrhea. C. trachomatis was the most prevalent pathogen across all test sites. The bacteria that cause gonorrhea and syphilis were found far less frequently, despite data showing confirmed cases of those diseases in the associated areas.Ìę

Further research could reveal why tests captured C. trachomatis more consistently than other STI-causing bacteria and explore the study’s limitations, which included people moving between sewer sites and the influence of demographics.

The researchers are also eager to investigate several trends they observed in the data, such as spikes in pathogen concentration occurring near the winter holidays and after Valentine’s Day.

Among the neighborhood collection sites was a small, densely populated area adjacent to a college campus. More than 87% of residents were young people between 18 and 34 years old, a population considered high-risk for STIs. Clinical health records showed very low case counts of chlamydia, but researchers consistently detected C. trachomatis in wastewater samples.Ìę

That gap could indicate underreporting driven by stigma or asymptomatic cases. It also gives public health officials an opportunity to react to a previously unknown increase in infection activity.

“From a public health perspective, data like this allows us to elevate awareness that this pathogen is here and spreading in the community, even if cases aren’t presenting to clinics or providers are not identifying the infections in their patients,” said co-lead author , program manager of the Washington State Department of Health’s wastewater surveillance program. “A small amount of wastewater can tell you so much about the community while simultaneously filling gaps in the traditional methods we monitor disease activity.”Ìę

A full list of co-authors is available with the paper.Ìę

This research was funded in part by the Epidemiology and Laboratory Capacity Infectious Diseases Cooperative Agreement from the U.S. Centers for Disease Control and Prevention.Ìę

For more information, contact Fuhrmeister at efuhrm@uw.edu.

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Once coyotes get a taste for city living, the call of the wild fades to a whisper. Food is abundant and predators are few. Research indicates that coyotes enjoy the benefits of urban areas enough to put up with all the people, and Seattle is no exception.

Over the past century, coyotes have colonized every major metropolitan area in North America. Chicago is home to an , and in Los Angeles, urban coyote density is at least seven times higher than in wild areas. Coyotes are often spotted in parks and neighborhoods , but the lack of formal data makes it difficult for researchers to track trends.

“We observed a ninefold increase in coyote density in Seattle compared to more natural and wild areas of the state,” said lead author , a UW professor of environmental and forest sciences. “That might surprise people who think of coyotes as afraid of humans, but I think it just shows how ideal the urban setting is for coyotes.”

The results in Environmental Research: Ecology.

In the study, researchers analyzed coyote scats collected throughout Seattle and from wild study areas near Winthrop in north-central Washington and Chewelah in the northeastern part of the state. They estimated density based on how often they picked up a scat from the same animal, identifying 261 total coyotes from 842 scats.

Researchers were also curious about factors that influence density within the city, such as the luxury effect — where wealthier neighborhoods have more plant and animal diversity. Researchers compared the coyote density maps to ones showing pollution level, tree cover, buildings and roads, human population density and income level. Of those factors, only human density seemed to influence the coyotes.

“In Seattle, human population density had a negative effect on coyote density. But when you compare coyote abundance in Seattle to areas with far fewer people, the coyote population was much higher in the city,” Prugh said.

Although coyotes are wary of people, the conditions that dense human populations create favor their survival. Urban coyotes are less likely to be killed or go hungry than their wild counterparts.

that fear of mortality may play a role in determining where coyotes live. In the wild, larger carnivores such as wolves and mountain lions hunt coyotes, but in cities they get to masquerade as apex predators. Farmers and landowners are also more likely to kill coyotes to protect their livestock in rural settings.

The only things that regularly kill urban coyotes are cars and disease.

Cities also offer a wider variety of food options for coyotes. Scat analyses showed that urban coyotes’ diets were more than twice as diverse as those of wild coyotes, although .

Rabbits are the choice prey for coyotes in most ecosystems and the abundance of one often impacts the other. Seattle’s over the past few decades changed urban ecology, and may have helped draw coyotes to the region.

“Coyotes and rabbits have a natural relationship, even in a highly altered environment like Seattle,” Prugh said. Rabbit density could be an even stronger predictor of coyotes than humans, she added, but there isn’t enough data to test the theory.

Although long-term coyote population data is also limited, there is overwhelming anecdotal evidence of coyote abundance increasing in the past few decades, Prugh said.

Sightings are more common at dusk and dawn, but coyotes are now as well. They tend to avoid people, but residents have raised concerns about coyotes and displaying territorial or behavior.

Because they are territorial, coyotes will fight each other over turf. This behavior helps control their population in the absence of other predators. Cities can only support so many coyotes, but Prugh isn’t sure whether Seattle has met that limit yet.

Either way, the coyotes aren’t going anywhere fast.

“One thing that coyotes have shown over and over is that they are incredibly resistant to control efforts,” said Prugh. “With enough food, they will just have more pups.”

The study also highlights some of the often overlooked ways that coyotes can benefit the ecosystem. For example, by munching on young plants, and coyotes help them by munching on rabbits.

“Whether there are too many or too few coyotes is sort of a societal question, but ultimately our answer might not matter,” said Prugh. “Coyotes are here to stay in cities, and it is up to us to learn how to live with them.”

Co-authors include , lab manager at the UW; of Purdue University; and of Colorado State University; of the Wildlife Institute of India; of New Mexico State University; and of the University of California Berkeley.

This research was funded by the U.S. National Science Foundation, the UW Royalty Research Fund, the Woodland Park Zoo, the Animal Welfare Institute and the Fulbright India program.

For more information, contact Prugh at lprugh@uw.edu.

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UPDATE Sept. 8, 2026: This story has been updated to correct the total increase in melt season since the 1980s.

Relatively few people have been to the Arctic, and even fewer have set foot in Antarctica. Most of us rely on our imaginations and media to visualize these landscapes and the ways they are changing.

Research shows that the Arctic is than the global average. The sea ice is melting, exposing more open ocean and throwing the ecosystem out of balance. The story of Antarctica contains fewer details, but emerging trends are concerning to researchers.

Conceptualizing this change can be challenging for those of us who have only glimpsed Greenland from the airplane window, but for someone with firsthand experience, it’s eye-opening.

, a research scientist at the șÚÁÏÀÏËŸ»ú’s Applied Physics Laboratory, has visited the Arctic at least once a year since 2009, sometimes staying for as long as five months.

Webster is the lead author of a new research paper, in Nature Reviews Earth and Environment, that describes how sea ice has changed in the past 50 years.

Their analysis arrives as the world begins preparations for the , a dedicated period of observation that will peak during the 2023 to 2033 season. International Polar years have occurred every 30 to 50 years since the late 1800s to advance polar research and track environmental change. The upcoming International Polar Year will occur just 25 years after the last, held in 2007, due to the acceleration of climate change.

What motivated this study?

Melinda Webster: We have known for a long time now that the extent, or area, and thickness of sea ice is declining, especially in the Arctic. But we wanted to take that a step further to examine the properties of the ice, especially perennial ice, which doesn’t completely melt away in summer. We updated trends for sea ice with 15 to 20 more years worth of data to understand how it has changed through the contemporary period. We also wanted to emphasize the divergent responses we see in the Arctic and Antarctica, and make recommendations for future research.

What did you discover?

MW: The Arctic sea ice melt season has gotten approximately seven and a half days longer per decade since 1979, and this is mostly driven by sea ice forming later in the fall. This has sweeping implications for the global climate system. The superpower of sea ice is its high albedo, meaning that it reflects a lot of sunlight — somewhere between 60% and 90% — back into space. Dark ocean water, on the other hand, reflects just 7%. The open ocean absorbs much more sunlight than ice does, and with that absorption comes warming. In the fall, the ocean is too warm for ice to form and it is taking longer for that heat to dissipate.

The seasonal ice that ultimately forms is thinner, and easier to melt in the following spring and summer. So this creates a cycle of warming that reduces ice coverage and increases the amount of energy in our climate system over time.

What’s the deal with Antarctica?

MW: Antarctica is a land mass covered in ice and surrounded by water. The Arctic is an ocean surrounded by land. Although they share certain qualities, the two regions are very different from one another, with distinct responses to climate change. For a long time, the sea ice cover wasn’t declining in Antarctica, but in the last four years the sea ice cover experienced record losses.

Logistically, it’s a lot more difficult to deploy instruments in the Antarctic than the Arctic. The measurements we do have are less accurate because the Antarctica sea ice system is more complicated. But, we need to unravel these recent changes, which is a priority research area we identify in the paper.

What other impacts do you foresee these changes having?

MW: Another key result we presented is that snow cover on Arctic sea ice has gotten thinner and the sea ice itself is smoother. That has huge repercussions for polar bears and seals, as it impacts their ability to build dens for raising their young.

There’s also a connection to fisheries. Changes in sea ice cover also impact algae, which form the base of the food web. These algae are accustomed to very low light conditions, but thinner snow and ice let more light in and the algae are essentially getting sunburnt.

When you take an ecosystem that was adapted to an ice environment and introduce open ocean, it disrupts its regular functioning. The health of algae impacts the entire food web, which has important implications for fisheries in the sub-Arctic and Arctic. Less food might mean fewer fish, and that introduces a whole new set of concerns.

Are there any potential solutions?Ìę

MW: To mitigate climate change, you have to reduce greenhouse gas emissions. That’s at the center of the problem. There are various alternative geoengineering strategies floating around but little consensus on how safe and useful they are.

I think that it is critical to have international regulations that are shaped by representative communities on what kind of research we need before any geoengineering action is taken, if at all. Still, at the end of the day, geoengineering is a Band-Aid. We need to reduce greenhouse gas emissions to deal with the underlying cause of climate change instead of just treating its symptoms.

I’m optimistic about solutions for reducing emissions. Technological and scientific innovation are progressing at a rapid pace, which gives me hope about the future.

Co-authors include of the University of Hamburg; of NASA Goddard Space Flight Center; of the Jet Propulsion Laboratory at California Institute of Technology; of Woods Hole Oceanographic Institution; of Université Catholique de Louvain; of the Finnish Meteorological Institute and of Hokkaido University.

This research was funded by the U.S. National Science Foundation, the U.S. Office of Naval Research, NASA, the Alfred-Wegener-Institut, Helmholtz-Zentrum fĂŒr Polar- und Meeresforschung, the University of Hamburg, the German Research Foundation, SnowCast, the DFG Emmy Noether Programme Project Snowflake and the Research Council of Finland.

For more information, contact Webster at melindaw@uw.edu.

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Motion-triggered cameras showcase the prevalence of ‘nectar robbing’ in Hawaiian flowers

Some long curved bills are the perfect implement for drawing sweet nectar from deep within a lobelioid flower. As birds reach into flowers to access the nectar stored near the base, their bills can brush against the ‘ pollen-bearing structures, making hungry honeycreepers important pollinators. But some of these specialized honeycreepers have gone extinct. Shorter-billed species can now “rob” nectar — without contacting the flower’s pollen-bearing structures — from the endangered flowers. A UW-led team used motion cameras to gauge how often nectar robbing occurs. The results, in Ecology and Evolution, reveal both nectar robbing and pollination visits, showcasing a broader pattern that the team previously identified . Nectar robbing can damage flowers and leave less nectar for other potential pollinators. The researchers 3D printed a bird bill to simulate nectar robbing and track changes in nectar availability and the plants’ ability to reproduce. Damaged flowers often struggled to replenish their nectar stores, but were still able to produce fruit and viable seeds. These studies are part of a that aims to catalog Hawaiian bird-plant interactions through time, specifically tracking how these interactions are reshaped by extinction.

For more information, contact lead author , a UW research scientist in the biology department, at sam.case24@gmail.com.

The other UW co-authors are , Christopher Steinbronn and . A full list of co-authors and funding is .

People with anxious attachment styles are more likely get emotionally involved with ChatGPT

rose to popularity in the late 20th Century as a way to categorize how people bond with others. Someone with an anxious attachment style, for instance, fears abandonment and rejection, whereas someone with an avoidant attachment style is independent at the cost of personal closeness. In , UW researchers explored how peoples’ attachment styles affect their interactions with ChatGPT. The team analyzed the chat histories of 105 young adults, each of whom completed an attachment-style survey. Researchers found that they could automatically detect peoples’ attachment styles based on their interactions with the chatbot. People with an anxious attachment style were more likely to be emotionally involved with the AI system, writing things like “Can you please love me?” and “I miss my ex and I can’t sleep because of it.” Anxious users were also more prone to trust ChatGPT and to follow its recommendations. The team argues that this highlights the need for policies that prohibit companies from psychologically profiling users without their consent, since it leaves them vulnerable to manipulation.

For more information, contact senior author , a UW associate professor in the Information School, at alexisr@uw.edu or lead author , a doctoral student in the Information School, at marxwang@uw.edu.

The other UW co-authors are , , and .

Nursing is a major energy suck, but it’s difficult to estimate the toll for many marine mammals

Marine mammals lactate like any other mammal, but the energetic demands are difficult to measure in wild animals and thus not well understood.Ìę Researchers are concerned that some marine mammals may not be getting enough food, which can lead to failure to reproduce and . To understand the link between nutritional status and reproduction, researchers need to know what marine mammals require to rear offspring. A published in PLOS One modeled the daily costs of lactation using data from semi-aquatic and terrestrial mammals to explore whether results could be generalized to other species, like whales and dolphins. Modeling could approximate lactation costs of certain understudied marine mammals, including seals and sea lions, but appeared unable to produce accurate estimates for whales and dolphins. Lactation costs increase over time for most animals, but seem to be higher early in lactation for marine mammals, possibly due to their fully aquatic lifestyle. The study highlights a need for other methods to fill the remaining data gap to better understand the impacts of environmental change on marine mammals.

For more information, contact lead author , a research scientist in the UW Cooperative Institute for Climate, Ocean, & Ecosystem Studies, at emchuron@uw.edu. Funding information is .

Simulations suggest that lasers could ‘calm’ persnickety plasma

could supply humanity with — provided that scientists and engineers can work out how to create sustained fusion reactions safely, efficiently and affordably. The trick is in the taming of , a superhot state of matter made of free-floating electrons and atomic nuclei. When compressed to outlandish pressures and temperatures in a reactor, the nuclei fuse with one another, releasing energy. In that extreme environment, plasma forms instabilities that can derail a fusion reaction; much fusion research is focused on “calming” volatile plasma. published in Physics of Plasmas, UW researchers and other collaborators simulated a novel strategy to control instabilities using two opposing laser beams. By tuning the lasers’ properties — such as their frequency and polarity — the researchers prevented instabilities from growing and cascading. Surprisingly, the lasers also delayed other instabilities within the plasma, even though they were not directly targeted by the laser fields. By taking advantage of interactions within the plasma, the researchers found a way to calm instabilities indirectly. The results could help experts develop algorithms that stabilize plasma in real time, sustaining fusion conditions long enough to produce useful energy.

For more information, contact , UW professor of aeronautics and astronautics at shumlak@uw.edu.

A full list of co-authors and funding is .

When exposed to air, new nanomaterial becomes magnetic at high temperatures

While fridge magnets are great for saving favorite recipes, modern magnetic materials are useful for improving fiber optics or quantum information sciences technology. If you zoomed in on most fridge magnets, you’d see the atoms arranged in a repeated lattice structure called a “spinel.” These structures are made up of three types of atoms, generically referred to as atoms “A,” “B” and “X.” In a paper in the Journal of the American Chemical Society, UW researchers describe two new spinels made of silver, chromium and selenium ions. These are among the first spinels to include a silver ion in the “A” slot, the slot that determines the “vibe” of the spinel, or how it will react to various stimuli, such as light, heat or air. When exposed to air, the original spinel loses silver ions and transforms into the second spinel. The second spinel maintains its magnetic properties up to 400 Kelvin, or 260 degrees Fahrenheit; the original loses its magnetism at 152 K, or -185 F. This is the largest change ever documented in what is known as the Curie temperature, or the highest temperature at which a material is still magnetic. The researchers plan to continue to explore these two materials and what they can teach us about the fundamentals of magnetism.

For more information, contact lead author , UW doctoral student in chemistry, at ekbacong@uw.edu.ÌęÌęÌęÌęÌę

The other UW co-authors are Charlize Agag, , , , Yinuo Xu, , , and . A full list of co-authors and funding is .

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Most of the stars in sit neatly on a flat plane. But the space around our galaxy is much more chaotic. Rogue bands of stars called “” orbit the Milky Way much like planets in our solar system orbit the sun.

Astronomers have long been fascinated by the possibility that stellar streams could indirectly reveal the presence of , that mysterious theorized substance that doesn’t interact with light or normal matter — except via gravity. However, a new șÚÁÏÀÏËŸ»ú study casts doubt on a leading theory linking dark matter and stellar streams, and raises new questions about both galactic phenomena.

“Dark matter makes up most of the mass in the universe and forms the scaffolding that galaxies grow on, but we still don’t know what it is,” said co-author , a UW assistant professor of astronomy. “The Milky Way is one of the best laboratories we have for figuring that out, and stellar streams are one of the sharpest tools inside it.”

in The Astrophysical Journal.

A stellar stream forms when a group of stars crashes into a galaxy and becomes ensnared by its gravity. As the stars orbit the galaxy, its gravity stretches the cluster into a . Most galaxies host stellar streams, though the Milky Way’s are the most visible to astronomers. 

In our galaxy, most stellar streams we can see are irregular — gaps and kinks interrupt an otherwise uniform smear of stars. Many astronomers believe that those irregularities could signal the gravitational tug from small clumps of dark matter, called subhalos. If there are indeed subhalos sprinkled throughout the galaxy, studying the aberrations in stellar streams could teach us about the composition of dark matter.

The new study was an effort to understand the role that the host galaxy — rather than the dark matter clumps within it — plays in shaping stellar streams. Astronomers simulated four Milky Way-sized galaxies without any dark matter clumps, then peppered them with roughly 15,000 stellar streams. After five billion simulated years, the team observed irregularities in nearly every stellar stream.

“In our simulations, the host galaxies alone caused the same kinds of irregularities that we observe in real stellar streams,” said lead author , a UW postdoctoral scholar in astronomy. “Now that we can predict what the host galaxy does on its own, we can start isolating the part that dark matter is responsible for.”

The cause of the irregularities was the structure of the galaxies themselves. In each simulated galaxy, stars were spread somewhat unevenly across the disc, creating areas of greater and lesser density to mimic the composition of a real galaxy like ours. As the simulated streams of stars passed through denser regions of space, they were bent and torn by the irregular gravitational landscape.

Arora expected the host galaxies to impart some irregularities on the streams, but the sheer number caught him off guard.

“We found that almost all of the streams had some sort of structural variation,” Arora said. “So this idea that streams are naturally thin and smooth wasn’t really necessarily true.”

The simulation generated wiggles, kinks, spurs, branches, gaps and clumps; some streams were totally torn apart by the gravitational froth of their host galaxies. Streams orbiting closer to the galactic core were thrown into dense clumpy regions of space more often, where they acquired more irregularities. Out of the 15,000 streams spread across the four host galaxies, only 70 remained perfectly smooth after five billion years. 

The results might seem disheartening, but the UW team believes they chart a clear and exciting course for the future of dark matter research. Arora wants to include dark matter clumps in the next simulation to see whether they produce stellar stream irregularities that are distinct from those caused by the host galaxy alone. 

There may also be opportunities to check simulations against new observations: the is , which will help astronomers build a taxonomy of stream features and — hopefully — discover fingerprints of dark matter.

“Sadly there’s no magic wand to reveal the structure of dark matter,” said , a research assistant professor of astronomy at the UW. “Streams are complex systems, but they’re still the most interesting way to study the dark matter close to home.” 

Co-authors from the UW astronomy department include , a postdoctoral fellow; , an undergraduate student; and and , graduate students.

A complete list of co-authors is .

This research was funded by the Gordon and Betty Moore Foundation.

For more information, contact Arora at arora125@uw.edu.

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Between 2021 and 2023, Antarctica appeared to be growing. Heavy snowfall fueled by wetter weather caused parts of the continent to gain mass, leading whether climate change is really causing the ice to melt. However, a new study shows that the precipitation increase was an anomaly related to extra warm tropical ocean temperatures, not part of a long term trend.

The results Aug. 19 in Nature.

Antarctica as warm water melts ice from below and sends large chunks crashing into the ocean. Annual precipitation can’t keep up with the rate of melt, causing a net mass loss. However, the snow that fell on East Antarctica, a vast area that contains nearly 80% of Earth’s land bound ice, added mass faster than the ice was melting. Although mass loss continued in West Antarctica, the general trend seemed encouraging.

“In the early 2020s, there was an exceptional amount of snowfall over parts of Antarctica. Because Antarctica is so big, it doesn’t take that much extra snow thickness to counter the loss of ice from the edges of the ice sheet, which led to the perception that the loss of ice is slowing down,” said co-author , a UW professor of Earth and space sciences.

The question nagging researchers was whether this would continue into the future. To answer it, they needed to trace the origins of the precipitation.

Because warm air can hold more moisture than colder air, higher latitudes could eventually see wetter conditions due to global warming. Scientists recognize that the average amount of moisture in the air will increase as global temperatures rise. Some saw the heavier snowfall as evidence that this expected trend was materializing in Antarctica.

“Warmer conditions favor storms shifting toward the poles, which could offset ice loss through snowfall,” said co-author Qinghua Ding, a professor of atmospheric and climate science at UC Santa Barbara.

But the data told a different story. Using a computational method that involves “tagging” water molecules, the researchers linked the extra precipitation in Antarctica to the tropical warm pool, a warm patch of ocean in the western Pacific and eastern Indian oceans that makes an outsized contribution to extreme weather.

Water temperature in the warm pool was notably higher than average between 2021 and 2023, triggering changes in atmospheric circulation that directed more moisture toward East Antarctica.

Historical evidence shows that multi-year warming of the warm pool is normal. Every few decades or so, it heats up for several years before reverting to its average temperature.

“When something changes, it is very tempting, even to scientists, to think ‘Oh, there’s a new normal happening,’ but this analysis shows that’s not the case. This is most likely a short-lived phenomenon,” Steig said.

The connection to global warming from human activity is tenuous, he added. It’s difficult to tease apart human impact from natural variability in the tropics, but because we see this pattern repeated in history, it is most likely just part of the natural background variability of the tropical climate system.

However, increased carbon dioxide emissions to the climatic conditions accelerating ice loss in West Antarctica.

As a whole, the Antarctic Ice Sheet covers an area larger than the U.S. and Mexico combined and stores most of Earth’s freshwater. It is also the greatest source of uncertainty in long-term sea-level rise projections. Understanding the balance between ice gain and loss in Antarctica helps researchers make predictions with global implications. Knowing the underlying dynamics provides important guidance for how to interpret new observations.

“There hasn’t been much attention paid to the particular mechanism we identify; this is a reminder to not interpret short term change as a long term trend,” Steig said.

“The climate system is complex,” Ding said. “Every year brings new surprises and we have to stay curious, humble and open-minded to improve our theories.”

Additional co-authors include and of the Chinese Academy of Sciences; of UC Santa Barbara; of the University of Alaska Fairbanks; of Dartmouth College and Dåniel Topål of Université catholique de Louvain.

This study was funded by the National Natural Science Foundation of China, the U.S. National Science Foundation, the U.S. National Oceanic and Atmospheric Administration, the U.S. National Aeronautics and Space Administration, JST PRESTO, Japan, the Japanese Ministry of Education, Culture, Sports, Science and Technology, and the Hungarian Academy of Sciences.

For more information, contact Steig at steig@uw.edu and Ding at qinghua@geog.ucsb.edu.

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Today’s wireless technologies harness chunks of the for myriad uses — radio waves broadcast TV and radio; microwaves transmit cellphone signals and cook our food; X-rays image our bodies; gamma rays kill cancerous cells.

, however, is interested in more neglected slices of the spectrum. Naghavi, an assistant professor of electrical and computer engineering at the șÚÁÏÀÏËŸ»ú, studies the “terahertz band,” a region of the spectrum . Terahertz frequencies are notoriously difficult to work with, but they hold enormous potential in the fields of sensing, imaging and communications — future sensors, for example, could help firefighters “see” through smoke during rescue operations.

Naghavi recently joined a cohort of researchers from across the country who were awarded grants by the U.S. Department of Energy’s , an initiative to apply artificial intelligence across a wide range of research areas; other UW researchers are part of a Genesis-funded project to advance AI-driven cosmology. With the grant, Naghavi plans to develop compact, efficient sensors that could enable wearable gadgets to image their environment in new ways.

UW News caught up with Naghavi to learn about his new project and how it extends his work on terahertz frequencies.

What is the terahertz band and why are you studying it?

Hossen Naghavi: The terahertz band is a segment of the electromagnetic spectrum that lies between 100 gigahertz and 10 terahertz — the microwave band sits below it, and the optical band sits above it. That position gives terahertz waves a unique combination of microwave and optical properties. Microwaves can see through opaque materials like clothing, smoke or fire, but their long wavelengths limit the resolution of microwave imaging. Optical waves have the opposite problem. Their wavelengths are short, so they produce high-resolution images, but most materials block visible light completely, which makes it impossible to see inside or behind an object.

Terahertz waves are a sort of “happy medium.” Their wavelengths are short enough to give useful resolution but long enough to see through many materials. That combination allows us to build new sensors and cameras that can detect concealed objects or image scenes through smoke, dust and other conditions that defeat conventional optics.

What are some applications you envision for terahertz frequencies?

HN: is expected to become a defining mode of human-computer interaction, but realizing its full potential requires machines that can perceive and understand their surroundings far beyond what the human eye can see. Consider a high-stakes setting such as firefighting, where an augmented reality headset powered by terahertz waves could help firefighters locate victims or identify hazardous materials through smoke, fog and debris.Ìę

Beyond firefighting and emergency response, terahertz technologies could also aid in autonomous navigation, security screening, industrial inspection, biomedical sensing, molecular spectroscopy, agricultural applications, and 5G and 6G communication networks.Ìę

Sounds exciting! What’s the catch?

HN: Sensors that use terahertz waves, like the ones in our firefighting headset example, have been demonstrated in the lab. However, low-cost, low-power electronics that would be practical in a wearable device have not yet been developed.

Terahertz sensors produce high-resolution image streams, and processing them conventionally means moving enormous amounts of data to a central processor for analysis by an artificial intelligence system. That consumes too much power and adds too much delay to be practical in a lightweight device meant to be worn all day.

Tell us about your new project. How will it address some of the hurdles facing terahertz technologies?

HN: The usual way to build a terahertz imager is to split the job in two. The radar sensor collects raw signals, and a separate processor turns the signals into a picture. That division sounds sensible, but it is the source of most of the trouble. The raw signals arriving at each of the sensor’s antennas are slightly out of step with one another, and the processor has to line them all up before an image can form. That alignment requires a lot of continuous computation, which drains batteries quickly and introduces lag.

The natural comparison is the human eye. Your retina does not ship every photon to your brain for interpretation. It processes what it sees on the spot and passes along something much more compact, which is part of why vision costs your body so little energy. We are trying to give a terahertz sensor the same quality, which is why we describe the design as “neuromorphic,” meaning “brain-inspired.”

Who are you working with on this technology, and what’s next?

HN: My group at the UW and ‘s group at Texas A&M University are designing and building the sensor hardware. at the University of Utah and at ChipNexus are developing and implementing the AI system. This is a highly collaborative project.

Our next big milestone is to demonstrate a terahertz neuromorphic imager as a proof of concept in Phase I of our Genesis Mission project. Moving forward, we hope to expand the project into Phase II to add even more capabilities and make this technology accessible for public usage as early as possible.

For more information, contact Naghavi at naghavi@uw.edu.

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Nearly 30 years ago, a simple question sent șÚÁÏÀÏËŸ»ú researchers into the Puget Sound lowlands to look for birds. With Seattle’s population swelling and housing developments pushing into once-forested suburbs, researchers wanted to know how land conversion was impacting birds, and whether the type of development mattered.

The researchers returned to various development sites three to four times a year to log which birds they saw and heard. They found that when developments preserved native vegetation and tree cover between homes, a wider variety of bird species remained. The difference was most significant to sensitive species that tend to avoid humans — like the and — which fared better in conservation-minded developments.

This study highlights a dynamic that is often overlooked under the assumption that all development is bad for habitat.

“This work shows that birds care how land is developed, which gives developers a choice during the planning process. There are tradeoffs between developments designed for humans and those designed with the ecosystem in mind, but balancing the two can benefit both,” said senior author , UW professor emeritus of environmental and forest sciences.

The results were in Scientific Reports.

For the study, researchers organized birds into three groups based on their adaptability. Avoiders included native forest birds such as chickadees, wrens and woodpeckers; adapters included sparrows and robins; and crows, pigeons and hummingbirds were among those classified as exploiters because they can benefit from development by visiting bird feeders and foraging on scraps.

The researchers returned to lowland sites several times a year during the spring and summer breeding season to look and listen for birds. Pairing visual and acoustic signals gave them a more complete bird census.

During the initial years of observation, when the habitat was changing but before construction began, species diversity increased at all development sites, but prolonged disturbance sent many native species into decline. This effect was more pronounced when housing density increased.

“The greatest species diversity was right in the middle years of development, likely due to an increase in habitat heterogeneity,” said lead author , who completed this work as a doctoral student of environmental and forest sciences at the UW and is now an associate professor at Seattle University. “Our Pacific Northwest forests aren’t terribly diverse as forests go, but when you start to mix that up by clearing trees, it opens the canopy to another suite of species.”

As construction progressed, avoider and adapter populations declined. Avoiders showed the most uniform response, but adapters were more split — some declined while others persisted. Exploiters were present in both development types, contrary to the researchers’ hypothesis that they would fare better in denser developments.

These results come at a pivotal moment for Washington’s avian residents. Earlier this year, Birds Connect Seattle describing declines in bird abundance and diversity throughout the city. Average bird counts are down 21% since the 1990s and species richness has dropped 18%. At the same time, developers are buying up tracts of timberland to build homes.

Just last week, bidding closed on the auction of in the Snoqualmie Valley, which could allow construction of up to 30 new homes.

“It’s becoming less and less profitable to keep land for timber than it is to sell it for home development,” DeLap said.

Even if development compromises habitat quality, knowing which factors support biodiversity could help developers balance profitability and ecosystem health.

These results underscore the need to consider sensitive species when planning projects, and caution surveyors against assuming that all birds within a guild will behave the same way. Changing the land will change the ecosystem, bringing birds together that might not have shared habitat otherwise.

“Given that a lot of forest land will likely be converted in the coming years, I hope this will help folks recognize what they stand to gain and lose through development,” DeLap said. “There might be other configurations worth evaluating, but now at least we know what happens on the landscape in these two scenarios.”

Additional co-authors include , a UW professor of aquatic and fishery sciences and leader of the USGS Washington Cooperative Fish and Wildlife Research Unit.

This study was funded by the U.S. National Science Foundation and the șÚÁÏÀÏËŸ»ú Rachel Wood’s Endowed Graduate Program and James W. Ridgeway Professorship.

For more information, contact DeLap at jdelap@seattleu.edu and Marzluff at corvid@uw.edu.

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