Thursday, August 13, 2026

GPS tracking study reveals why invasive barred owls are winning the battle for California's old-growth forests, and how barred owl management is giving spotted owls a fighting chance

GPS data from 56 owls show the invader occupies the best old growth, and managing it back reopens habitat spotted owls can use

Integral Ecology Research Center

Invasive barred owl in northwestern California old-growth forest — image:
A barred owl (*Strix varia*) peers from behind a moss-covered trunk at night in northwestern California. Native to eastern North America, the species has invaded the range of the northern spotted owl, where GPS tracking of 56 individuals showed it selects the tallest, oldest, most structurally complex forest—the same stands spotted owls need to nest and roost. Nearly two-thirds of the average barred owl territory fell within mapped spotted owl habitat.
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Credit: J. Mark Higley

BLUE LAKE, Calif., Aug. 13, 2026 - Newly published research offers some of the clearest evidence yet of why the invasive barred owl has become one of the greatest threats to the northern spotted owl, and delivers encouraging evidence that managing barred owl populations can restore old-growth habitat for spotted owl recovery.

The study, led by scientists at the Integral Ecology Research Center (IERC) and published in the journal Biological Conservation, used GPS trackers on 56 barred owls across 4,070 square kilometers of forest in northwestern California. It is the first study to use GPS telemetry to determine, bird by bird, exactly which forest features invasive barred owls select, and how much old-growth habitat each one occupies.

The results are striking. Barred owls, native to eastern North America but now widespread across the West, consistently chose the tallest, oldest, and most structurally complex stands of forest: the same towering, dense-canopy, big-tree habitat that spotted owls need to nest and roost. On average, 64% of a barred owl's home range overlapped with mapped spotted owl habitat, and 38% was the very highest-quality nesting and roosting forest on the landscape.

Barred owls also claimed far more space in California than they do at home. Each bird's territory averaged 6.7 square kilometers, roughly 28 times larger than the home ranges IERC researchers previously measured for barred owls in their native range in Louisiana. That means every invading owl exerts outsized pressure on the old-growth forest, and the wildlife within it, well beyond what its native ecology would predict.

The most encouraging finding, however, is what happens once barred owls are managed out of an area. Because the forest structure itself remains intact, researchers found that managing a single resident pair out of a territory reopens several square kilometers of habitat that spotted owls can reclaim. Drawing on 1,171 barred owls removed under an ongoing, permitted regional research and management program, the study conservatively estimates that more than 1,800 square kilometers of spotted owl habitat, including nearly 1,150 square kilometers of the best nesting and roosting forest, have been freed up for spotted owl recolonization.

"Every stand of that forest still shows up as spotted owl habitat on our maps," said Dr. Vitek Jirinec, research scientist at IERC and lead author of the study. "But habitat isn't just trees, it's trees a spotted owl can actually live in, and barred owls have taken that off the table across much of the landscape. Managing the invader is proving just as critical as protecting the trees themselves."

Because barred owls are generalist hunters, they compete with spotted owls for staple prey like flying squirrels and tree voles while also preying on dozens of species spotted owls rarely touch: salamanders, reptiles, and even small carnivores like the western spotted skunk. Researchers say this concentrated pressure likely extends beyond spotted owls to the broader old-growth community, an implication the team says warrants further study.

"Spotted owls are the reason this study exists, but they're part of a much larger old-growth food web, one where every species plays a role in keeping the system intact," said Dr. Greta Wengert, Co-Founder and Co-Director of IERC and principal investigator on the study. "This means protection of the old-growth biological community requires staying committed to managing this invader for the long haul. This is exactly the kind of science IERC specializes in: rigorous enough for a peer-reviewed journal, specific enough for a manager to rely on for years to come."

The findings add scientific weight to ongoing regional efforts to manage barred owl populations, carried out in partnership with the University of Wisconsin-Madison, U.S. Department of Agriculture, Hoopa Valley Tribe, U.S. Forest Service, California Department of Fish and Wildlife, and other regional partners. The research was funded primarily by the California Department of Fish and Wildlife's Cannabis Restoration Grant Program.

About the Integral Ecology Research Center

Founded in Blue Lake, California, in 2004, IERC is a nonprofit conservation science organization dedicated to studying and conserving wildlife and the ecosystems they rely on across California and beyond. IERC partners with tribal, state, and federal agencies, as well as academic institutions, to conduct scientific research, from field ecology to molecular ecology, that translates directly into on-the-ground conservation action for species such as the northern spotted owl, Humboldt marten, and Pacific fisher. Learn more at IERCecology.org.

Publication: Jirinec, V., Gabriel, M.W., Higley, J.M., et al. 2026. Invasive barred owls select old-forest structure: Functional habitat loss for spotted owls and a threat to old-forest fauna. Biological Conservation 322, 112035.

Open Access at: https://doi.org/10.1016/j.biocon.2026.112035

Barred owl perched in mature closed-canopy forest, northwestern California

A barred owl (Strix varia) perches beneath closed canopy in northwestern California. GPS tracking of 56 individuals showed that this invasive congener selects forest with high canopy cover, tall stands, large-diameter trees, and diverse tree sizes—the structural signature of mature forest and the same conditions northern spotted owls require for nesting and roosting.

Credit

Daniel Hofstadter

Journal

Biological Conservation

DOI

10.1016/j.biocon.2026.112035

Method of Research

Observational study

Subject of Research

Animals

Article Title

Invasive barred owls select old-forest structure: Functional habitat loss for spotted owls and a threat to old-forest fauna

Article Publication Date

7-Aug-2026

Sensory overload makes it harder for female treefrogs to select a mate

When faced with too many mating calls, female treefrogs take longer to decide or abandon the search altogether

Smithsonian

Cope’s gray treefrogs in amplexus 1 — image:
Cope’s gray treefrogs in amplexus, the characteristic mating posture of frogs.
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Credit: Jessie Tanner

When shopping for a new appliance, choosing a movie to watch or even ordering a cup of coffee, people often experience “choice overload.” New research from the Smithsonian suggests that female Cope’s gray treefrogs face a similar challenge when selecting a mate. In a study published today in iScience, researchers from the Smithsonian Tropical Research Institute and the University of Tennessee found that when female treefrogs are confronted with too many males calls at once, they become less likely to successfully choose a mate. The findings reveal how cognitive limits may influence mating behavior not only in treefrogs but across the animal kingdom.

During the breeding season across eastern North America, Cope’s gray treefrogs gather in large choruses with males calling simultaneously to attract females. The resulting wall of sound can make it difficult for females to identify a suitable mate. Previous research has focused on “energetic masking,” in which overlapping calls make individual males difficult to hear. But few studies have explored choice overload, where frogs are confronted with too many calls at once. To separate the effects of these two phenomena, researchers played recorded mating calls throughspeakers in a laboratory and measured female responses when confronted with increasing numbers of potential mates, varying levels of background noise, or both.

“We were really interested in disentangling why female treefrogs have trouble finding a mate, whether it’s because they have trouble hearing males against a noisy backdrop, or if the females simply become overwhelmed by the number of options,” said Claire Hemingway, a research associate at the Smithsonian Tropical Research Institute, an assistant professor at the University of Tennessee and the lead author on the paper. “In human terms, is it like entering a crowded bar and not being able to hear anyone talk, or is it like using a dating app and not being able to choose among the many options?”

The researchers presented females with one target mating call and varying numbers of competing calls. As the number of options increased, the frogs’ ability to make decisions declined. When presented with only two calls, females pursued their mate 97% of the time. When the number of calls increased to eight, the proportion dropped to 82%. Even when females did make a choice, they were less likely to select the target call, and it took significantly longer for them to decide. With two calls, females selected the target 76% of the time and reached it in an average of 114 seconds. With eight calls, target selection fell to just 25%, and decision times increased to 183 seconds.

“We were shocked by how straightforward the results were,” said Jessie Tanner, an assistant professor at the University of Tennesee and the paper’s senior author. “With or without noise, when we presented more calls to the females at once, their performance declined in several ways, making the effect of choice overload clear."

The findings demonstrate that treefrogs, like humans, are susceptible to choice overload and suggest that cognitive constraints may play a larger role in sexual selection among animals than previously recognized. By highlighting the limits of how animals process information in complex environments, the research opens new avenues for understanding how cognition affects mate choice and evolution across species.

About the Smithsonian Tropical Research Institute

Headquartered in Panama City, Panama, STRI is a unit of the Smithsonian Institution. Our mission is to understand tropical biodiversity and its importance to human welfare, to train students to conduct research in the tropics and to promote conservation by increasing public awareness of the beauty and importance of tropical ecosystems. Watch our video, and visit our website, Facebook, and Instagram for updates.

Journal

iScience

DOI

10.1016/j.isci.2026.117086

Method of Research

Experimental study

Subject of Research

Animals

Article Title

Choice overload constrains mate choice independent of energetic masking

Article Publication Date

12-Aug-2026

Cope’s gray treefrogs in amplexus, the characteristic mating posture of frogs.

Credit

Jessie Tanner

Cope's gray treefrog

Cope's gray treefrog

Credit

Cody Stricker

The testing arena viewed from overhead,

Cope’s gray treefrogs in amplexus, the characteristic mating posture of frogs.

Credit

Jessie Tanner

Credit

Jessie Tanner

Unexpected findings add new insight on cannabis and heart health

UCSF trial found fewer premature heartbeats after cannabis inhalation, with potential implications for atrial fibrillation risk

University of California - San Francisco

Habitual cannabis users experienced about 9% fewer premature heartbeats on days they inhaled cannabis compared with days they abstained, a counterintuitive finding that adds to the complex and evolving understanding of how cannabis affects the heart, new UC San Francisco-led research found.

The study, published Aug. 12 in the Journal of the American College of Cardiology, is among the first to examine the acute cardiovascular effects of inhaled cannabis in people living their normal daily lives. While the findings challenge assumptions drawn largely from observational studies, the researchers caution these findings should not influence medical or behavioral decisions around cannabis use.

With millions of Americans using cannabis, studies like this are increasingly important to understand its health effects, said researchers.

"We were surprised by the results because they contradicted our original hypothesis," said Gregory Marcus, MD, MAS, an endowed professor in atrial fibrillation research in the UCSF Division of Cardiology. "That's why randomized trials are so important. When the data challenge our expectations, our job as scientists is to understand them, not ignore them."

The trial enrolled 108 adults who regularly smoked or vaped cannabis but had no history of clinically diagnosed cardiac arrhythmias. Over 14 days, participants were randomly assigned each day to either inhale cannabis or abstain while wearing a continuously recording electrocardiographic monitor, activity tracker, sleep monitor, and continuous glucose monitor. Participants served as their own control, allowing investigators to compare physiological changes during cannabis-use and abstinence days.

Greatest predictor of premature atrial contractions

Unlike previous studies that relied largely on participants' self-reports or medical records, this randomized crossover trial, the gold standard for trials, continuously monitored every heartbeat, enabling researchers to measure physiological changes in real time under everyday conditions.

Researchers found that cannabis inhalation was associated with a statistically significant reduction in extra or early heartbeats, knowns as cardiac ectopy. The reduction was driven by fewer extra heartbeats that began in the heart's upper chambers, known as premature atrial contractions (PACs). The frequency of PACs is the single most potent predictor of atrial fibrillation, while PVCs can predict heart failure. Although these early heartbeats are common, researchers still know relatively little about what determines their frequency.

No significant change was observed in extra heartbeats originating in the lower chambers, called premature ventricular contractions (PVCs).

The researchers found no significant differences in daily step counts, sleep duration, or glucose levels, also surprising. Together, the findings illustrate how randomized trials can produce a different and more nuanced picture than observational research alone.

Marcus emphasized that the findings should not be interpreted as evidence that cannabis benefits cardiovascular health.

"This study examined the acute effects of cannabis in people who use it regularly and was not designed to evaluate the long-term health consequences," he said. "The overall health effects of inhaled cannabis may still be net negative, but these findings suggest there may be something about cannabis that can teach us more about the biological mechanisms that produce premature atrial contractions. That knowledge could eventually lead to new approaches for preventing or treating abnormal heart rhythms."

Authors: In addition to Gregory M. Marcus, MD, MAS, the study authors are Adi Elias, MD, MPH; Gabrielle C. Montenegro, BA; Hannah H. Oo, BS; Isabella J. Peña, BA; Dylan A. Lowe, PhD; Catherine Lee, PhD; Janet Tang, PhD; Kara L. Lynch, PhD; Lilly Lim, BS; Mirna Maamou, BS; Nhung Nguyen, PhD; and Matthew L. Springer, PhD, of UC San Francisco.

Funding: The research was supported by the UCSF Cardiology Scholars & Innovation Award. Dexcom donated continuous glucose monitors used in the study.

Disclosures: The authors report no relevant conflicts of interest or disclosures.

About UCSF: The University of California, San Francisco (UCSF) is exclusively focused on the health sciences and is dedicated to promoting health worldwide through advanced biomedical research, graduate-level education in the life sciences and health professions, and excellence in patient care. UCSF Health, which serves as UCSF’s primary academic medical system, includes top-ranked specialty hospitals and other clinical programs, and has affiliations throughout the Bay Area. UCSF School of Medicine also has a regional campus in Fresno. Learn more at ucsf.edu.

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Journal

Journal of the American College of Cardiology

DOI

10.1016/j.jacc.2026.07.014

Method of Research

Randomized controlled/clinical trial

Subject of Research

People

Article Title

Acute Effects of Cannabis Inhalation on Cardiac Ectopy, Physical Activity, Sleep, and Glucose

Article Publication Date

12-Aug-2026

Smokers still largely unaware of heart disease risks

A new study covering 46 countries found significant gaps in awareness about smoking and second-hand smoke

University of Waterloo

An international study has found that despite two decades of global tobacco control efforts, the message still is not getting through to enough smokers that smoking and second-hand smoke cause heart attack and stroke.

Researchers at the University of Waterloo and the Global Tobacco Control Program at the U.S. Centers for Disease Control and Prevention (CDC) conducted the study, which is the largest of its kind.

Tobacco use is the leading preventable cause of disease and death worldwide. Up to two-thirds of people who smoke throughout their lives die from a smoking-caused disease, and lose more than a decade of life, on average.

The research team analyzed data from more than 240,000 adult smokers across 46 countries over two decades. While more than 90 per cent knew that smoking causes lung cancer, only about 80 per cent knew it causes heart disease or heart attack and 70 per cent knew it causes stroke. In several high-income countries — including Australia, Germany, England, the U.S., New Zealand, and Canada — fewer than half of adults who smoke knew that second-hand smoke causes heart disease or heart attack. China, a country of 300 million smokers, was among the countries where awareness was lowest.

“Knowledge gaps about the major health effects of smoking and second-hand smoke are deeply concerning,” said Dr. Janet Chung-Hall, Research Scientist for the International Tobacco Control Policy Evaluation Project (ITC Project) at Waterloo and the lead author of the study. “The low awareness of the cardiovascular harms of smoking and second-hand smoke is particularly troubling given that smoking causes more than 2 million cardiovascular deaths worldwide each year. Increasing public awareness of these risks should be a greater public health priority.”

Across two decades, the study found almost no progress in knowledge of the health risks of smoking and second-hand smoke. Although knowledge about the cardiovascular risks of smoking and second-hand smoke increased in some countries, including Bangladesh, India, Thailand and Vietnam, knowledge of those second-hand smoke risks actually decreased in the majority of high-income countries studied, including Canada, the U.S., New Zealand, England, and Japan.

The study also examined knowledge about lung cancer, finding that although about 90 per cent knew that smoking causes lung cancer, fewer knew that secondhand smoke does, with little progress over time.

“Knowledge is an important first step toward quitting smoking and protecting others from second-hand smoke,” said Dr. Geoffrey T. Fong, Principal Investigator of the ITC Project and University Professor of Psychology and Public Health Sciences at Waterloo. “Our findings highlight the need for governments to implement stronger, sustained public education about the cardiovascular as well as cancer risks of smoking and second-hand smoke. Policies such as large pictorial warnings and sustained media campaigns can increase awareness, encouraging quitting among those who smoke and discouraging young people from starting to smoke.”

Those policies are part of the global tobacco control treaty, the WHO Framework Convention on Tobacco Control, to which more than 180 countries are signatories.

The study appears in BMJ Open.

Journal

BMJ Open

DOI

10.1136/bmjopen-2025-107667

Method of Research

Data/statistical analysis

Subject of Research

People

Article Title

Smokers still largely unaware of heart disease risks

Article Publication Date

4-Aug-2026

Solar Power Is Gaining Traction With Farmers

By Felicity Bradstock - Aug 12, 2026

Agrivoltaics allows crops, livestock, and solar generation to coexist on the same site, potentially increasing total land productivity and farmer revenue.
Governments are increasingly creating policies and development frameworks that accommodate solar on agricultural land, including a new statutory definition of agrivoltaics in Virginia.
The EU Joint Research Centre estimates that agrivoltaics on just 1% of EU utilized agricultural land could accommodate around 944 GW of solar capacity.

As energy companies explore innovative ways to increase clean power production and gain public support for new projects, many solar firms are investing in developing dual-purpose operations that utilise agricultural land for solar farms. A common criticism of solar farms is that installing panels on arable land for the sole purpose of energy production restricts land use for other purposes. However, installing solar panels on agricultural land, where farming practices can still take place, could provide a solution to the problem.

Many solar projects are being developed on arid, nonarable land which would not otherwise be developed. However, solar cells typically function more effectively in humid, rather than dry, conditions. But developing solar farms on arable land has garnered political opposition and public criticism in the past. Meanwhile, the not-in-my-backyard opposition to solar projects continues to be a major deterrent for development. However, using solar panels on land already developed for agriculture can allow for clean energy production while appeasing critics.

Agrivoltaics, also known as agrophotovoltaics, agri solar or agri-PV, have started to grow in popularity and scale in recent years, as clean energy companies invest in developing dual-use sites. Solar panels can be installed above or around land used for crop production or livestock grazing.

Dual-use land has become popular among the farming community, as it offers farmers an opportunity to gain additional income from the same land they use for their agricultural activity. In addition to diversifying revenue sources, installing solar PV on farmland can have ecological advantages while reducing land-use competition and siting restrictions.

Solar panels are positioned so crops have access to sunlight but provide shade for crops and livestock during the most intense hours of sunlight and heat. They can also help stop water from evaporating from the soil. Meanwhile, crops growing underneath solar panels emit water vapour, which can help cool the panels from below and help them function more efficiently.

California plans to develop giant solar fields across tens of thousands of acres of fallow agricultural land that has been left idle due to water shortages. Roughly 70,000 acres of former farmland in the San Joaquin Valley west of Fresno have been forced to idle by the local water agency. As we are experiencing more frequent periods of drought in several parts of the world, developing dual-use projects can help farmers to keep their land even when it is not productive. The private developer Golden State Clean Energy is working with the water agency and farmers to develop the land for clean energy production.

Golden State plans to install up to 21 GW of solar panels and 21 GW of battery storage across 136,000 acres over the next decade as part of its Valley Clean Infrastructure Plan. Once complete, it is expected to provide enough clean power for over 10 million homes. The plan will consist of between 30 and 60 individual projects, with Golden State developing just 5 to 10 per cent of the solar farms, leaving the remaining sites open for other investors. The megaproject is expected to help California achieve its aim to get 100 per cent of its energy from renewable sources by 2045.

Meanwhile, in Virginia, the data centre development capital of the United States, the state government is exploring ways to boost energy production as the power demand continues to rise. In June, Virginia codified a state definition for agrivoltaics in a bid to encourage developers to invest in projects across the state.

A 2020 law requires Virginia’s two largest utilities to develop over 16 GW of land-based renewable energy, mostly solar power. However, solar developments have been widely demonised in the state, as they have been blamed for Virginia’s rapid loss of farmland – even though housing developments have contributed far more to this phenomenon. This led almost two-thirds of Virginia counties to outlaw or severely restrict large-scale solar. Developing solar projects on farmland could, therefore, help meet Virginia’s energy demand while responding to public concerns.

It is not just the United States that is developing its agrivoltaics sector, as several other parts of the world welcome investment. Research by the European Commission’s Joint Research Centre has shown that agrivoltaics could provide hundreds of gigawatts of solar capacity across Europe while only using a small proportion of the region’s agricultural land. Deploying agrivoltaics on roughly 1 per cent of Europe’s agricultural land could generate hundreds of terawatt-hours of electricity annually without restricting agricultural activity. In December, Greece announced plans to develop 130 MW of agrivoltaics across the country.

Developing dual-use land for agriculture and clean energy production could help optimise the use of arable land or provide an alternative use for idle land. It also provides additional income to farmers, many of whom face climate change challenges that are threatening their livelihoods. The use of agrivoltaics could also help clean energy companies to garner public and government support for projects on arable land.

By Felicity Bradstock for Oilprice.com