Ecologists have long sought clarity on the dietary habits of different animal species. For scientists at Brown University and the National Park Service, it wasn’t obvious how herbivores in Yellowstone National Park, who subsist on grasses, wildflowers and trees, could compete for enough of those foods to survive the winter.

Over two years, with the aid of cutting-edge molecular biology tools and GPS tracking data, the researchers were able to determine not only what herbivores in Yellowstone eat, but also what strategies the animals use to find food throughout the year. The team published its findings in Royal Society Open Science.

“In Yellowstone, we know vegetation changes across seasons, but until now, we didn’t know how these seasonal changes influenced what animals eat or how they sustained themselves when options were limited,” said lead study author Bethan Littleford-Colquhoun, a postdoctoral research associate at Brown.

“It turns out that while species eat similar categories of food, their diets differ from one another in cryptic and nuanced ways. And an animal’s body size plays an important role in how this is achieved.”

For decades, ecologists have debated how wildlife should confront challenges with their food supplies, said co-author Tyler Kartzinel, an associate professor of ecology, evolution and organismal biology at Brown.

Some experts argue that animals should diversify their diets to satisfy their taste preferences when they have the most freedom to select their favorite foods in summer, Kartzinel said. Others have posited that animals should diversify what they eat when they’re forced to accept whatever happens to be available—such as in a hard winter when they may have to compete for even undesirable foods to survive.

“These opposing predictions couldn’t both be true, so it wasn’t at all clear how Yellowstone’s assemblage of herbivore species—with such a diversity of foraging behaviors—could succeed in finding enough food throughout the year,” Kartzinel said.

Seasonal specialization

For the study, the researchers used two years of GPS tracking and dietary DNA data to elucidate dietary variation across times of resource limitation and resource abundance for five of Yellowstone’s best-known species: bison, elk, deer, bighorn sheep and pronghorn antelope.

Scientists and staff at Yellowstone tracked the animals. Researchers at Brown, many of them undergraduate students overseen by Littleford-Colquhoun, analyzed fecal samples using a sophisticated molecular technique called metabarcoding, which helped to identify what foods the animals had consumed.

They found that all species capitalized on the seasonal abundance of wildflowers in summer, and that each species consolidated its foraging efforts around the subset of plant types that it was best prepared to compete for in winter. But the researchers discovered that feeding behaviors depended on the animal’s body size.

Members of the smallest species, such as deer and sheep, tended to fan out across summer meadows and dramatically expanded their diets before gathering in protected valleys where they survived the winter on leftover plants, according to the study. Larger animals like bison tended to do the opposite: In the winter, they were large enough to avoid competing for dwindling resources, so they instead ventured out into deep snow to find unique food reserves inaccessible to smaller deer and sheep.

“The study showed that these species can feed far more adaptably than anyone had previously assumed,” Littleford-Colquhoun said. “All species switch the ways they search for food, but the opportunities an individual bison has to fuel its migration or survive a hard winter might only work for it because it’s big. Meanwhile, other species might need to group together for protection in winter because they’re small.”

So when should animals search for unique foods to diversify their diets—summer or winter? Kartzinel said it depends on the kind of animal.

“Because of the variety of ways animals behaved in our study, we learned that both hypotheses about how animals fuel their migrations were right, but in different ways and at different times,” Kartzinel said.

“So the question that biologists should have been bickering about for the past generation shouldn’t have been, ‘Which foraging strategy is right?’ but rather, ‘When does each strategy work best for a given group of animals?'”

Kartzinel hopes the more nuanced insights about foraging behavior will help scientists take a more customized approach to wildlife conservation.

“If we want to help wildlife populations thrive,” Kartzinel said, “we should be maintaining a diversity of habitats and plant resources across their migratory corridors so that many animals, each with their own preferences, personalities and needs, can find what’s best to fuel their journey.”

A team of physicists and engineers affiliated with several institutions in China has developed an extremely small nuclear battery that they claim is up to 8,000 times more efficient than its predecessors. Their paper is published in the journal Nature.

Scientists have been looking for a way to create tiny nuclear power packs for decades. These could power virtually any device, from phones to robots and cars, for many years. Unfortunately, the development of such power packs has been stymied by the dangerous nature of nuclear power plants, regardless of size.

One approach is the development of devices powered by batteries that are charged by nuclear material. Such devices have tended to be small to reduce the amount of nuclear material needed, which has reduced the potential amount of power they could produce. They are also extremely inefficient.

In this new study, the research team found a way to create such a device that is far more efficient.

The device designed and built by the researchers is relatively simple and straightforward. They placed a small amount of americium into a crystal and then used its radiated energy (alpha particles) to produce light. The result is a crystal that glows green.

They connected the crystal to a photovoltaic cell that converts the light to electricity. The device was then placed inside a quartz cell to prevent radiation leakage.

In testing their device, the team found that it could remain charged for a long time—perhaps as long as decades. They note that the half life of americium is 7,380 years, but the radiation would erode the materials housing it long before that.

Further testing showed the device to be approximately 8,000 times more efficient than any other nuclear-powered battery system developed to date, though they note that the amount of power produced is very small—it would take 40 billion of these power packs to light a 60-watt bulb.

The researchers suggest further refinement could lead to tiny power packs for small, remote devices such as those sent into deep space.

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A new international collaborative study provides a list of the wildlife species present at the market from which SARS-CoV-2, the virus responsible for the COVID-19 pandemic, most likely arose in late 2019. The study is based on a new analysis of metatranscriptomic data released by the Chinese Center for Disease Control and Prevention (CDC).

The data come from more than 800 samples collected in and around the Huanan Seafood Wholesale market beginning on January 1, 2020, and from viral genomes reported from early COVID-19 patients. The research appears September 19 in the journal Cell.

“This is one of the most important datasets that exists on the origin of the COVID-19 pandemic,” says co-corresponding author Florence Débarre of the French National Center for Scientific Research (CNRS). “We’re extremely grateful that the data exist and were shared.”

“This paper adds another layer to the accumulating evidence that all points to the same scenario: that infected animals were introduced into the market in mid- to late November 2019, which sparked the pandemic,” says co-corresponding author Kristian Andersen of Scripps Research.

“We have analyzed, in new and rigorous ways, the vitally important data that the Chinese CDC team collected,” says co-corresponding author Michael Worobey of the University of Arizona. “This is an authoritative analysis of that data and how it fits in with the rest of the huge body of evidence we have about how the pandemic started.”

On January 1, 2020, after the animals were removed and just hours after the market was closed, investigators from the Chinese CDC went to the market to collect samples. They swabbed the floors, walls, and other surfaces of the stalls; they came back days later to focus on surfaces in stalls selling wildlife, such as a cage and carts used to move animals, and then also collected samples from the drains and sewers.

They performed metatranscriptomic sequencing of the samples, a technique aiming to obtain all RNA sequences (and which can pick up DNA as well) from all organisms present in the samples—viruses, bacteria, plants, animals, humans. The Chinese CDC team, led by Liu Jun, published their data and results in 2023 in the journal Nature.

However, the article left unresolved the exact identities of the animal species found in the data that could represent plausible intermediate hosts. The Chinese CDC shared their sequencing data on public and open repositories.

According to the latest analysis of the data being published in Cell, SARS-CoV-2 was present in some of the same stalls as wildlife sold at the market—including raccoon dogs (small fox-like animals with markings similar to raccoons) and civet cats (small carnivorous mammals related to mongooses and hyenas).

In some cases, genetic material from the SARS-CoV-2 virus and these animals was even found on the same swabs. The exact animal species were identified by genotyping their mitochondrial genomes in the samples.

“Many of the key animal species had been cleared out before the Chinese CDC teams arrived, so we can’t have direct proof that the animals were infected,” Débarre says. “We are seeing the DNA and RNA ghosts of these animals in the environmental samples, and some are in stalls where SARS-CoV-2 was found too. This is what you would expect under a scenario in which there were infected animals in the market.”

“These are the same sorts of animals that we know facilitated the original SARS coronavirus jumping into humans in 2002,” Worobey adds. “This is the most risky thing we can do—take wild animals that are teeming with viruses and then play with fire by bringing them into contact with humans living in the heart of big cities, whose population densities make it easy for these viruses to take hold.”

The international team also performed evolutionary analysis of the earliest viral genomes reported in the pandemic, including these environmental sequences, and inferred the most likely progenitor genotypes of the virus that infected humans and led to the COVID-19 pandemic.

The results imply that there were very few, if any, humans infected prior to the market outbreak. This is consistent with spillovers from animals to humans within the market. There may also have been spillovers of limited impact in the immediate upstream animal trade.

“In this paper, we show that the sequences linked to the market are consistent with a market emergence,” Débarre says. “The main diversity of SARS-CoV-2 was in the market from the very beginning.”

The new study landed on a short list of animal species in the wet market found co-occurring or close to viral samples that could represent the most likely intermediate hosts for SARS-CoV-2. The common raccoon dog, a species susceptible to SARS-CoV-2 and that carried SARS-CoV in 2003, was found to be the most genetically abundant animal in the samples from market wildlife stalls.

Genetic material from masked palm civets, which were also associated with the earlier outbreak of SARS-CoV, was also found in a stall with SARS-CoV-2 RNA. Other species such as the Hoary bamboo rat and Malayan porcupines were also found to be present in SARS-CoV-2-positive samples, as well as a multitude of other species.

While the data cannot prove whether one or more of these animals may have been infected, the team’s analyses provide a clear list of the species that most plausibly could have carried the virus and genetic information that could be used to help trace where they originated.

The investigators stress the importance of understanding the origins of the COVID-19 pandemic, especially in light of other recent spillovers, such as the spread of avian flu viruses in cattle in the United States. “There has been a lot of disinformation and misinformation about where SARS-CoV-2 originated,” Worobey says.

“The reason it’s so important to find out is that this affects national security and public health, not just in the United States but around the world. And the truth is, since the pandemic started more than four years ago, although there has been an increased focus on lab safety, not much has been done to decrease the chance of a zoonotic scenario like this happening again.”