How horses whinny: Whistling while singing

Cell Press

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A horse mid-whinny.

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Credit: Elodie Briefer

A horse’s whinny is an unusually distinctive mix of sounds including both high and low frequencies. Reporting in the Cell Press journal Current Biology on February 23, researchers demonstrate how horses produce high-frequency sounds that defy their large size while simultaneously producing lower tones: they whistle through their larynx while vibrating their vocal folds as a human does while singing. Horses likely evolved these vocalizations to be able to convey multiple messages to one another at the same time, says the team.  

“We now finally know how the two fundamental frequencies that make up a whinny are produced by horses,” says author Elodie Briefer of the University of Copenhagen. “In the past, we found that these two frequencies are important for horses, as they convey different messages about the horses’ own emotions. We now have compelling evidence that they are also produced through distinct mechanisms." 

While domesticated horses have lived closely with humans for over 4,000 years, horse vocal communication is poorly understood. Larger mammals generally make lower-pitched sounds because the size of the larynx typically increases in step with body size. But researchers have noted exceptions to this rule—and horses' whinnies are a prominent example. 

To learn more, the team sought to explore the mechanics behind horses’ whinnies. They found that the whinny represents an unusual vocal phenomenon, known as “biphonation,” in which a vocalization has two independent frequency components: low and high.  

While the low frequency is made by vocal-fold vibration, just like a human singing or a cat meowing, the origin of the high-frequency component has remained mysterious until now. To learn more about this high-frequency sound, the team gathered a wide range of data through careful study of the animals’ vocal anatomy, clinical data, and acoustic analysis.  

"Solving this biomechanical puzzle required combining approaches from veterinary medicine to acoustic physics,” says author Romain Lefèvre of the University of Copenhagen. 

They found that the high-frequency component of the whinny is generated by a laryngeal whistle. The researchers describe it as similar in principle to a normal human whistle, except that the turbulent airstream that creates the whistle sound is created within the horse's larynx. Although some small rodents like rats and mice produce laryngeal whistles, horses are the first large mammal species found to whistle in this way and the only animals known to do so simultaneously with vocal-fold vibration. 

To demonstrate this whistle, the researchers performed excised larynx experiments, blowing a stream of air through the larynx removed from deceased horses. While doing so, they switched the airstream into the larynx from air to helium and back again. They explained that because the speed of sound is higher in helium, it causes whistles to shift to higher frequencies, while the frequency of normal vocal-fold vibration remains unchanged. As predicted, the high-frequency component of the whinnies shifted upward when using helium, while the low frequencies did not change. 

"When we blew helium through the larynges for the first time, the frequency shift was immediately obvious, and we knew we'd solved the mystery,” says author William Tecumseh Fitch of the University of Vienna. “We were thrilled!" 

The new findings help to explain how the two overlapping pitches—or biphonation—occur, says the team. They suggest that horses’ biphonation likely evolved to convey multiple independent messages concurrently.  

The researchers also note that Przewalski's horses—a species closely related to the domesticated horse—also produce whinnies with biphonation, but more distant horse relatives like donkeys and zebras appear to lack the high component of the whinny, suggesting that horses have unique vocal adaptations which allow them to produce a richer and more complex spectrum of calls compared to other mammals. 

"Understanding how and why biphonation has evolved is an important step towards elucidating the origins of the amazing vocal diversity of mammalian vocal behavior,” says author David Reby of the University of Lyon/Saint-Etienne. 

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This work was supported by the Swiss National Science Foundation, the Austrian Science Fund, and Institut Universitaire de France. 

Current Biology, Lefèvre et al., “The high fundamental frequency in horse whinnies is generated by an aerodynamic whistle” https://www.cell.com/current-biology/fulltext/S0960-9822(26)00004-7

Current Biology (@CurrentBiology), published by Cell Press, is a bimonthly journal that features papers across all areas of biology. Current Biology strives to foster communication across fields of biology, both by publishing important findings of general interest and through highly accessible front matter for non-specialists. Visit: http://www.cell.com/current-biology. To receive Cell Press media alerts, contact press@cell.com. 

Horse whinny [AUDIO] |

Journal

Current Biology

DOI

10.1016/j.cub.2026.01.004 

Method of Research

Experimental study

Subject of Research

Animals

Article Title

The high fundamental frequency in horse whinnies is generated by an aerodynamic whistle

Article Publication Date

23-Feb-2026

 

Roadmap for Europe’s biodiversity monitoring system

New study charts how digital technologies, DNA, and coordinated governance can transform biodiversity observation across Europe and support global conservation goals.

German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig

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Europe-wide monitoring is designed to track biodiversity change and support nature conservation. The photo shows a beech forest in the Hainich National Park, Thuringia, Germany.

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Credit: Stefan Bernhardt, iDiv

Biodiversity is changing across the planet, yet governments still lack the robust, consistent data needed to track these changes and guide effective conservation. Now, a new study led by the University of Amsterdam (UvA), the German Centre for Integrative Biodiversity Research (iDiv), and the Martin Luther University Halle-Wittenberg (MLU), proposes a comprehensive roadmap to build a modern, integrated Biodiversity Observation Network (BON) for Europe – one that could become a global model for biodiversity monitoring in the 21st century. The study has been published in the journal Nature Reviews Biodiversity.

“Our proposal provides a plan for Europe to fix its messy and disconnected monitoring systems,” says lead author Dr Daniel Kissling, Associate Professor at the UvA. “We want to create one coordinated, continent-wide network that can track changes in species and ecosystems – from the DNA of plants and animals to entire forests, rivers, and oceans.”

A unified monitoring system for Europe’s biodiverse heritage

The roadmap identifies 84 Essential Biodiversity Variables (EBVs) that form the backbone of a harmonised monitoring system. These EBVs – from bird abundance and insect phenology to seagrass extent, genetic diversity, and ecosystem productivity – provide Europe with a consistent, standardised checklist for measuring the state and change of its biodiversity.

“Europe has hundreds of monitoring programmes, but the data are often siloed, incompatible, or incomplete,” says senior author Prof Henrique Pereira, research group head at iDiv and the MLU. “Our roadmap provides the architecture for a truly integrated, transnational system – one that brings all observations together into a coherent whole.”

To enable this transition, the authors propose establishing a European Biodiversity Observation Coordination Centre (EBOCC). This new EU-level body would coordinate workflows, harmonise methods, ensure transparent data governance, align monitoring with EU policy needs, and act as the central hub for national and European data infrastructures.

High-tech biodiversity monitoring with people

A key message of the roadmap is that Europe must harness the combined strengths of technological innovation and human expertise, including the potential of new digital technologies, including:

• Automated digital sensors such as acoustic bird recorders, wildlife and insect cameras, and biological and weather radars
• AI for species recognition and automated data processing
• Environmental DNA (eDNA) and metabarcoding for detecting species and communities from water, soil, or air
• State-of-the-art remote sensing from satellites (including Copernicus), aircraft, and drones to observe habitats, vegetation structure, and ecosystem change

The roadmap also highlights that people remain central to biodiversity monitoring. Citizen scientists, taxonomic experts and professional monitoring networks provide essential observations, expertise, and continuity. New technologies complement and strengthen their contributions, making biodiversity monitoring more efficient, scalable and inclusive, while ensuring that human knowledge and engagement remain fundamental to Europe’s monitoring system.

Bridging data gaps through unified workflows

Europe’s current biodiversity data are extensive but scattered. The roadmap proposes to build data pipelines that can integrate information from many different sources – like professional field notes, reports from the public, electronic sensors, DNA samples, and satellite images, and merge them into scalable EBV datasets.

These new pipelines should enable Europe to create clear reports for decision-makers, spot trends quickly, and give early warnings of ecological change.

Step forward for international biodiversity policy

The roadmap was designed by EuropaBON, a Horizon 2020 project involving 15 research organisations across Europe and has led to a strong policy response, as the European Parliament has already approved a preparatory action for the EBOCC to start implementing parts of the roadmap. The roadmap for the EBOCC is directly aligned with the EU Biodiversity Strategy for 2030, the Nature Restoration Regulation (NRR), and other major EU environmental legislation, including the Birds Directive, Habitats Directive, Water Framework Directive, and Marine Strategy Framework Directive. By delivering harmonised biodiversity data, an EBOCC would significantly improve reporting and support implementation across Member States.

Globally, the system would help track progress toward the Kunming–Montreal Global Biodiversity Framework (GBF), support assessments of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), and contribute to GEO BON (Group on Earth Observations Biodiversity Observation Network).

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Journal

Nature Reviews Biodiversity

DOI

10.1038/s44358-026-00140-6 

Method of Research

Commentary/editorial

Subject of Research

Not applicable

Article Title

Building the backbone for Europe’s biodiversity monitoring

Article Publication Date

23-Feb-2026

 

Plant hormone therapy could improve global food security

Colorado State University

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By genetically manipulating the hormonal response of a commonly studied plant, Arabidopsis thaliana, scientists have harnessed the best of both worlds – immunity and productivity – and they believe this can be reproduced in crops. Credit: Colorado State University

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Credit: Colorado State University

Plants have an immune system, like people, and when it is triggered by threats like disease or pests, a plant's defenses are activated. But there’s a downside to this protective mechanism: The plant’s growth is suppressed when its immune system is turned on.

Colorado State University researchers have found a way to boost a plant’s growth while maintaining its immunity through a hormone treatment that shows promise for food production.

A plant threatened by disease will defend itself by producing hormones that can keep the plant alive but also stunt its growth – which is a problem if the plant is needed for food. By genetically manipulating the hormonal response of a commonly studied plant, scientists have harnessed the best of both worlds – immunity and productivity – and they believe this can be reproduced in crops. Their findings were published Feb. 23 in Current Biology.

"Only time will tell once it's integrated into crops what effect this will have, but it does have the potential to be as big of a breakthrough as the Green Revolution 60 years ago in terms of food security,” said Cris Argueso, an associate professor in CSU’s Department of Agricultural Biology and senior author of the study.

During the Green Revolution, geneticist and plant pathologist Norman Borlaug identified a wheat mutation that dramatically increased yield. He developed cultivars that were grown around the world, preventing famine. Borlaug is credited with saving a billion people from starvation and received a Nobel Peace Prize for his discovery. Downsides of the Green Revolution included widespread use of chemical fertilizers and pesticides and environmental degradation.

If the CSU researchers are successful in genetically altering crops to be more productive and disease resistant, the crops will need less fertilizer to grow and fewer chemicals to prevent disease, making this revolution “greener.” Of course, adding fertilizer will always enhance growth, even in plants that are naturally productive; but for now, the researchers are focused on integrating these beneficial traits into important food crops – wheat, corn and soybeans.

“We want to create crop plants that can defend really well against pathogens but don't have a yield penalty, which is the dream for farmers,” Argueso said. "We joke that this is the ‘green’ Green Revolution.”

The plant’s ‘chemical brain’

One similarity between Borlaug’s work and Argueso’s is that her lab is also working with a hormone mutant. The researchers studied a model plant species called Arabidopsis thaliana, also known as thale cress, a well-known plant in the mustard family. They selected plants of this species that had an autoimmune mutation that prevents them from thriving – like having an autoimmune disorder. 

Plants react to the constantly changing conditions surrounding them through plant-specific hormones called phytohormones. Argueso calls this the plant’s “chemical brain.” When plants are stressed by pests or disease, cytokinin hormones, which are responsible for cell division, are suppressed in a growth-defense tradeoff. By understanding phytohormone interactions and restoring cytokinin levels in the plants with overactive immune systems, the scientists were able to restart growth without negatively impacting the plant’s defenses. In fact, the plants they designed were even more resistant to disease.

While the researchers’ approach relies on genetic manipulation to change a plant’s chemical signals, it is much faster and easier than identifying and altering the specific gene responsible by mapping the plant’s entire genome, as is standard practice for modifying crop traits. Argueso likens their simpler solution to how a doctor might prescribe a pill to correct a chemical imbalance. She expects the mutations they’ve developed to be useful for agriculture for decades.

“We are exploring collaborations with breeding programs across the world, so this can be tested in different regions with all sorts of crops,” Argueso said. "If these mutations have the potential that we think they do, we would like them to be used everywhere.”

Student research

The study was funded by the National Science Foundation and led by Grace Johnston, who conducted the research as a student. Johnston was recruited into Argueso’s lab as an undergraduate biology student and wrote the paper as her master’s thesis. She is now a research associate in the lab.

"I did not know I wanted to do plant science,” said Johnston, who credits Argueso’s mentoring for her achievement and love of plant biology. "By the time I was done with my undergrad degree, we still didn't know enough about these plants, and I just couldn't let it go.”

Johnston received prestigious fellowships from the National Science Foundation and the American Society of Plant Biologists to support her work while earning her undergraduate and graduate degrees.

"This is a CSU research success story,” Johnston said. "Cris took me on when I didn’t know anything about science, and here we are eight years later, and we have the opportunity to actually impact food security.”

Argueso is passionate about inspiring young researchers like Johnston. Students from her lab have gone on to receive important national and international awards, and currently three undergraduate researchers are part of her team.

Second author Hannah Berry was a CSU Cell and Molecular Biology graduate student in Argueso’s lab; she is now a scientist at Pairwise, a plant biotechnology and gene-editing company. Co-author Hitoshi Sakakibara, a plant science professor at Nagoya University and the RIKEN Center for Sustainable Resource Science in Japan, is one of the top plant hormone quantification experts in the world. Mikiko Kojima, a scientist at the RIKEN Center for Sustainable Resource Science, also contributed to the study.

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Journal

Current Biology

DOI

10.1016/j.cub.2026.01.060 

Article Title

IMMUNE ACTIVATION SUPPRESSES REPRODUCTIVE GROWTH IN ARABIDOPSIS THROUGH CYTOKININ SIGNALING

Article Publication Date

23-Feb-2026

EPA criminal sanctions align with a county’s

wealth, not pollution

Washington State University

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PULLMAN, Wash. – When the federal government brings its toughest environmental enforcement actions against polluters, they tend to be in communities of greater wealth, not the most polluted places.

That’s the takeaway from a new paper co-authored by a Washington State University researcher that examined criminal prosecutions by the U.S. Environmental Protection Agency from 2011 to 2020 in every U.S. county. The findings were published in the journal Nature Sustainability.

“You might reasonably expect the government to use its most consequential enforcement mechanism in the counties that are the most polluted,” said Erik Johnson, a professor in WSU’s Department of Sociology and a co-author of the new paper. “But it turns out they use it in the wealthier counties more. The more educated and wealthy the county is, the more likely the government is to enforce environmental regulations.”

Criminal prosecutions, which can result in jail time, substantial fines and tax penalties, are the most serious enforcement actions taken by the EPA for violations of laws such as the Clean Water Act and Clean Air Act. They are much rarer than civil cases, where the EPA may seek monetary fines.

Drawing on a dataset of 732 criminal prosecutions brought in 432 of the 3,143 U.S. counties, the team mapped where enforcement actions occurred and analyzed correlations among a range of socioeconomic and environmental factors. Past research has established that low-income people and people of color face disproportionate environmental harm, and federal regulators have at times adjusted their priorities to bring more attention to these disparities.

But in the recent analysis, the strongest correlation was found between enforcement actions and higher socioeconomic status. According to the findings, a county ranked in the 84th percentile of socioeconomic measures would have 24% more enforcement actions than a county at the median of socioeconomic measures, on average. This trend held true in both the Obama and first Trump administrations.

 Researchers found no correlation between enforcement and measures of water and air quality, as tracked in the EPA’s Environmental Quality Index. Counties with better land quality were actually more likely to see increased enforcement actions.

The researchers said the study does not make any claims about the overall prevalence of environmental crimes, given that environmental violations are underreported and rarely rise to the level of federal prosecution. Among the possible reasons for the enforcement pattern is a growing focus by regulators on individuals and smaller companies, as large industrial polluters – which are responsible for the most pollution – are often able to settle cases or avoid prosecution based on their legal resources. 

There also may be institutional dynamics related to resource constraints, legal barriers, agency leadership and other organizational factors.

“These geographic patterns in EPA criminal prosecutions aren’t necessarily a result of an intentional or overt process,” said Pierce Greenberg, an assistant professor of sociology at Clemson University and lead author of the paper. “We're trying to identify the geographic patterning, and offer some explanations for why that might be. For example, counties that are farther away from a criminal enforcement office have fewer criminal prosecutions. So these organizational and institutional factors may be driving some of these trends.”

Greenberg earned his PhD at WSU in 2018, then worked at Creighton University before moving to Clemson. The other co-authors were Jennifer Schwartz, James F. Short Distinguished Professor in the Department of Sociology at WSU, and Rylie Wartinger, a graduate student at Clemson.

Johnson said the disparities in enforcement – which fit into the larger context of how widening income inequality plays out in people’s lives — raise questions about how well enforcement actions align with the purpose of environmental laws.

“What's the enforcement doing?” he said. “Is it responding to pollution in a pretty objective way? Or is it responding to community pressure where the community has enough economic status to press the issue?”

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Journal

Nature Sustainability

DOI

10.1038/s41893-025-01736-0 

Method of Research

Data/statistical analysis

Article Title

Social factors shape federal environmental crime prosecution patterns in the USA