Lower access to air conditioning may increase need for emergency care for wildfire smoke exposure

As Los Angeles County battles the most destructive wildfires in its history, a new study suggest that US policies should prioritize equity and education regarding the measures people can take to protect themselves from pollutants in wildfire smoke.

Boston University School of Public Health

FOR IMMEDIATE RELEASE

 January 10, 2025

Lower Access to Air Conditioning May Increase Need for Emergency Care for Wildfire Smoke Exposure

As Los Angeles County battles the most destructive wildfires in its history, a new study suggest that US policies should prioritize equity and education regarding the measures people can take to protect themselves from the harmful pollutants in wildfire smoke. 

People who have limited access to air conditioning may be at higher risk of seeking emergency care for health problems following exposure to wildfire smoke, according to a new study led by Boston University School of Public Health (BUSPH). 

Posted online ahead of publication in the journal Environmental Research: Health, the study found that exposure to fine particle matter (PM2.5) from wildfire smoke in California is associated with higher rates of emergency department visits for all causes, non-accidental causes, and respiratory disease. This risk varied by age and race, but was especially high for individuals who lived in areas with lower availability of air conditioning.

The findings come at a critical time, as firefighters in Southern California continue to battle multiple wildfires that have been blazing in and around Los Angeles County since Tuesday, January 7—including the Palisades fire, which is likely the largest and most destructive wildfire in the county’s history. Health experts are urging residents who are not under evacuation orders and can safely remain in their homes to turn on air conditioners and/or air purifiers if they have access to these devices.

Despite this guidance—and the growing threat of more frequent and intense wildfires due to worsening climate change—very little research has examined how the health effects of wildfire smoke exposure may differ based on individuals’ access to air conditioning. Understanding this relationship can inform policies and interventions that mitigate barriers to air conditioners and protect vulnerable populations from the consequences of inhaling PM2.5 and other harmful pollutants from this smoke, which can permeate the air from hundreds or thousands of miles away.

“Depending on the type of system and filter used, air conditioning may modify the impact of smoke exposure on human health,” says study lead and corresponding author Dr. Jennifer Stowell, research scientist in climate and health at BUSPH, noting that the analysis only addressed the likelihood of access to air conditioning, rather than air conditioning types or actual usage. “Studies like these will become more and more relevant as wildfire exposure increases. California is, perhaps, the best example of this in the US, with bigger fires and longer fire seasons. An important next step will be to identify ways to better characterize access to air conditioning.”

For the study, Dr. Stowell and colleagues from BUSPH, Boston University College of Arts & Sciences (CAS), and the Health Effects Institute utilized a nationwide dataset of healthcare claims to assess more than 50,000 emergency department visits during the 2012-2019 California wildfire seasons, which occurred from May to November each year. They quantified the adverse health effects from PM2.5 exposure among all study participants, as well as subgroups of participants. 

Consistent with prior research, wildfire smoke exposure was most strongly associated with emergency department visits for respiratory issues, but not cardiovascular-related complications. These visits were generally higher among children under 10 years old, adults between 20-74 years old, and among the Black population, although also elevated among White, Hispanic, and Asian/Pacific Islander populations. 

People living in areas with lower availability of air conditioning had a 22-percent greater risk of visiting the emergency department for respiratory conditions associated with wildfire smoke exposure. Greater insight into air conditioning use as a pollutant-filtering tool and the barriers that certain populations face in accessing these cooling systems is critical, as wildfires are expected to occur more regularly in the Wildland-Urban Interface (WUI)—areas where human activity is in close contact with sources of dry fuel. This is exactly what is happening now in LA County, Dr. Stowell says, as the fires destroy thousands of homes and businesses near vegetation.

“WUI fires are particularly concerning due to the burning of manmade structures and the additional toxic chemicals and particulates that can be found in their smoke plume,” says Dr. Stowell. “The current fires in LA are out-of-season fires driven by severe Santa Ana winds coming from the mountains. As climate change continues, the temperature differentials between land and sea will grow and, potentially, drive stronger and stronger late-season or out-of-season wind events.”

So how may residential air conditioners help dispel PM2.5 from homes? The filters in these cooling systems can remove particulate matter, although certain filters are more effective at filtering particulate matter than others. “HEPA filters can remove the majority of particles greater than 0.3 µm, but they are significantly more expensive than fiberglass air filters, which only remove larger particles and may allow high amounts of fine particulate matter to penetrate indoors,” Dr. Stowell says. “Generic pleated air filters are also fairly efficient at filtering out most particulate matter.” 

Air conditioning systems with a Minimum Efficiency Reporting Value (MERV) rating of seven or higher are thought to be the most efficient at removing particulate matter from outdoor air, but are also more expensive.

The study findings indicate a need for stronger policy measures that can reduce the health risks associated with wildfire smoke exposure.

"Many homeowners do not understand the differences between MERV ratings and how these might impact your health,” Dr. Stowell says. “Policymakers should consider delivering better information to the public—such as the types and ratings of filters that perform better—especially for those who reside in smoke-prone regions.” 

Given that marginalized populations appear to be disproportionately burdened by the health effects of wildfire smoke exposure, economic assistance should also be considered, she says, particularly for low-income populations residing in smoke-prone regions. “Considering the current fires in CA, local and state governments should heighten their responses to these events and develop plans and policies to reduce exposure before the fires occur,” Dr. Stowell says.

The study’s senior author is Dr. Gregory Wellenius, professor of environmental health and director of the Center for Climate and Health at BUSPH. The study was coauthored by Dr. Ian Sue Wing, professor of earth and environment at CAS; Dr. Yasmin Romitti, staff scientist at the Health Effects Institute, and Dr. Patrick Kinney, Beverly Brown Professor of Urban Health at BUSPH.

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About Boston University School of Public Health

Founded in 1976, Boston University School of Public Health is one of the top ten ranked schools of public health in the world. It offers master's- and doctoral-level education in public health. The faculty in six departments conduct policy-changing public health research around the world, with the mission of improving the health of populations—especially the disadvantaged, underserved, and vulnerable—locally and globally.

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DOI

10.1088/2752-5309/ad976d 

Method of Research

Observational study

Subject of Research

People

Article Title

Emergency department visits in California associated with wildfire PM2.5: differing risk across individuals and communities

COI Statement

Dr. Wellenius serves as a consultant for the Health Effects Institute (Boston, MA) and Google, LLC (Mountain View, CA). Dr. Sue Wing serves as a consultant for Lawrence Berkeley Laboratory (Berkeley, CA) and the European Commission Joint Research Centre (Seville, Spain).

 

CDC awards $1.25M to engineers retooling mine production and safety

University of Arizona College of Engineering

 

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Students enter the University of Arizona San Xavier Mining Laboratory.

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Credit: University of Arizona Lowell Institute for Mineral Resources

From mapping ore to predicting slope behavior and reclaiming land, mining is a rapidly evolving technological industry. Yet planning and operations have not necessarily kept up with the advancements. 

With $1.25 million from the National Institute for Occupational Safety and Health, or NIOSH, mining and geological engineering researchers in the University of Arizona College of Engineering are boosting their efforts to better align technology and planning for improved safety and productivity.

The award from the institute, part of the Centers for Disease Control and Prevention, will fund the research of six U of A graduate students for the next five years.

"With this award, we are able to train graduate students in important areas and generate cutting-edge research that not only adds to the body of knowledge, but also contributes to the mining industry," said associate professor Angelina Anani, who is leading the project in partnership with professor Moe Momayez and assistant professor Nathalie Risso.

Increasing production at home

The demand for minerals on which technologies such as laptops and electric vehicles are dependent – copper, lithium and cobalt, for example – is at an all-time high. But according to the national Government Accountability Office, the United States is heavily reliant on foreign countries for its supply. By some estimates, more than 80% of the nation's minerals comes from foreign sources.

A renewed federal focus on American-made products and domestic supply chains is challenging the mining industry to increase productivity while continuing to prioritize worker safety. 

These NIOSH-funded projects are geared toward improving the entire lifecycle of a mine – from rock assessment to post-mine land use – fundamentally changing how mines are planned and operated, said Anani. 

Making better decisions, faster

Anani's group of researchers is investigating dynamic mine planning – a contemporary technique that feeds big data collected during production into artificial intelligence models – providing mine operators with information they need to make better decisions, faster. 

"We have not figured out the best way to extract information from that data and apply it to operations in a sustainable way," she said. "Our idea is to take that data and update each stage of the mine planning process by using technologies such as machine learning."

For example, companies could use dynamic mine planning in slope assessments to better predict collapses, which are costly and put workers at risk.

Momayez is using advanced geotechnical methods to evaluate subsurface conditions and map ore deposits.

Presently, mines rely on exploratory boreholes to assess rock condition, but deposits can stretch for miles.

"We're focusing on using geophysical techniques to create a continuous map of geological properties and ore grade before mining," he said, adding that such mapping ties in to dynamically predicting slope behavior.

Aligning automation and safety

Nathalie Risso, director of the university's Mine Automation and Autonomous Systems Laboratory, also is keen on orienting operations to safety regulations and productivity. 

"There are a lot of standard operating procedures that are associated with how the mining equipment is supposed to work," she said. "But when you have autonomy, those are not going to apply, so with this research we seek to create new methods to make mining safer and more productive."

The researchers are investigating how autonomous mining vehicles are used in other countries and will provide recommendations for updated regulations in the U.S.

"It is a reimagining of mine planning," said mining doctoral student Tinotenda Blessing Chimbwanda, who is working with Risso and Anani. "Autonomous vehicles bring new risks in terms of how they interact with other equipment.

"The whole idea about mining for me is to make sure that everyone goes home safe and uninjured." 

Chimbwanda is one of the graduate students supported by the CDC award; funding is still available for five other students with professors Anani, Risso or Momayez serving as their advisers.

 

An eye-opening year of extreme weather and climate

Institute of Atmospheric Physics, Chinese Academy of Sciences

 

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Extreme climate and weather events in 2024

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Credit: Wenxia Zhang

From the persistent droughts of southern Africa and Central America in the early part of the year to the more recent devastating extreme rainfall in Spain and the deadly Hurricane Helene along America’s east coast, 2024 has been a year of climate events that affected the lives of billions of people.

 

In a recent paper published in Advances in Atmospheric Sciences, an international team of scientists led by Dr Wenxia Zhang at the Institute of Atmospheric Physics, Chinese Academy of Sciences, provide an overview of the characteristics and impacts of the most notable extreme events of the year, including rainfall and flooding, tropical cyclones, and droughts. Moreover, they discuss their causes, the role of global warming, and the challenges we face in the future to be “climate-resilient”. Dr Zhang and her team have been conducting an annual review of the global climate extremes since 2022, and this year they found it to be marked by exceptional rainfall and flooding.

 

“Most extreme events have a large random element in that they are subject to fluctuations in the weather, and occur when weather patterns set up in just the 'right' way.  Some extremes are more likely when larger-scale drivers such as ENSO influence the weather patterns in a region,” says Dr James Risbey at CSIRO, coauthor of the study.

 

In particular, many of the extreme rainfall and drought events of 2024 were related to the atmospheric configurations associated with the El Niño in winter 2023/24. However, ENSO does not fully explain individual events. Layered on top of that, according to studies of extreme event attribution, or “attribution science”, we know that human-induced climate change since the pre-industrial era has in many cases exacerbated extreme rainfall, tropical cyclones, and droughts, and therefore their associated socioeconomic impacts.

 

“The climate change influence can be direct through physical processes causing the extreme, or indirect in influencing the weather, large scale drivers, and key baselines,” adds Dr Risbey.

 

“This is consistent with basic physical understanding that anthropogenic warming leads to increases in atmospheric moisture and evaporative demand, and hence, potentially enhances extreme rainfall and droughts, respectively”, explains Dr Wenxia Zhang.

 

Despite our understanding of why the world is experiencing increasingly strong and frequent extreme climate events, the research team behind this study make it clear that key challenges remain in our knowledge and attribution of these phenomena—not least the often seen inconsistencies between observed and modeled extremes (especially for extreme rainfall), which limits our confidence in attribution results.

 

“Improved extreme event attribution requires better understanding of climate change”, says Dr Micheal Brody of George Mason University (USA) and the International Agricultural University (Uzbekistan), another of the paper’s authors. “More accurate attribution of extreme events is expected to inform decision-making, ranging from post-disaster recovery to future preparedness”.

 

Another crucial angle to this annually developing story of our climate is our ability to accurately forecast and broadcast the occurrence of extreme events, and then to act appropriately. Doing so could save many of the lives of the people that otherwise fall victim to the floods and hurricanes like those seen in 2024.

 

“Some of the extreme events witnessed in 2024, such as Hurricane Helene, were well forecasted”, notes Dr Zhuo Wang from the University of Illinois, another member of the team. “The destructive impacts were partly due to the vulnerability of the underprepared community to a changing climate”.

 

Dr Piotr Wolski, University of Cape Town, adds: “Increasing the quality of forecasts is important, but to reduce the impacts of extreme events, it is more important to achieve proper dissemination of warnings and to act upon them to lessen existing vulnerabilities”.

 

Dr Wolski's comments refer to the idea of being “climate-resilient”, which is fast becoming a crucial aspect in our holistic approach to climate change and the effects it is having on our society. As we shift to a feeling of almost inevitability that this is our world now, there is a rising sense of what can be done to protect ourselves alongside how to prevent the problem in the first place.

 

As we saw in Valencia, Spain, following the devastating floods and mudslides there in October, it does not take much for the impacts of extreme climate events to manifest as frustration and anger among the people affected.

 

Clearly, it is more urgent than ever to not only work towards better understanding the drivers of extreme weather and climate, but also to better predict their occurrence and develop effective systems to rapidly act upon the information at hand.

 

Only then can we be better prepared  for years like 2024.

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Journal

Advances in Atmospheric Sciences

DOI

10.1007/s00376-025-4540-4 

Article Title

A year marked by extreme precipitation and floods: Weather and Climate Extremes in 2024

Article Publication Date

11-Jan-2025

 

Sea surface temperatures and deeper water temperatures reached a new record high in 2024

Institute of Atmospheric Physics, Chinese Academy of Sciences

 

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The ocean surrounding the Antarctic continent is experiencing one of the fastest warming rates.

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Credit: Chao Ban

A new study published in Advances in Atmospheric Sciences has found that ocean warming in 2024 has led to new record high temperatures. The ocean is the hottest it has ever been recorded by humans, not only at the surface temperature but also for the upper 2000 meters.

“The broken records in the ocean have become a broken record.” Said Prof. Lijing Cheng with the Institute of Atmospheric Physics at the Chinese Academy of Sciences. He led a team of 54 scientists from 7 countries and discussed how a hotter ocean affects our lives on land and what this means for our future.

Why is the ocean so important?

The ocean is a critical part of the Earth’s climate – most of the excess heat from global warming is stored in the ocean (90%) and the ocean covers 70% of the Earth’s surface. Because of this, the ocean dictates our weather patterns by transferring heat and moisture into the atmosphere. The ocean also controls how fast climate change happens.

“To know what is happening to the climate, the answer is in the ocean.” Said Prof. John Abraham at the University of St. Thomas, coauthor of the study. 

Results from three international teams who collaborated on this project were consistent – the ocean is warming, and 2024 was a record. The next image shows one set of results for the upper 2000 m ocean heat content (from the Institute of Atmospheric Physics). Blue and red colors refer, respectively, to whether a particular year was colder or hotter than the 1981-2010 period.  This time period is used as a basis for scientists to compare against reference conditions. The central message is that the values have been increasing year after year after year.

From 2023 to 2024, the global upper 2000 m ocean heat content increase is 16 zettajoules (1021 Joules), ~140 times the world's total electricity generation in 2023. 

“OHC has increased steadily by 15~20 ZJ over the past five years despite the La Niña and El Niño cycles.” Said Prof. Michael Mann from University of Pennsylvania.

The ocean surface temperature is also setting records. The surface temperature refers to temperatures just at the surface, where the ocean waters and atmosphere commute. Surface temperatures are important because they dictate how fast heat and moisture (humidity) can transfer from the ocean to the air and thus affect weather. The rise in surface temperatures since the late 1950s has been staggering.

Why does this matter?

The changes are not uniform; regional variations can be substantial. The Atlantic is warming along with the Mediterranean Sea, and across the mid-latitude Southern Ocean. While parts of the Northern Pacific Ocean have warmed very rapidly, other areas (the tropical region) have not, mostly due to the La Nina/El Nino cycle in that area. The heat has even accumulated near both the North and South Poles.

A warmer ocean affects marine life and result in huge damage in many ways.

“The main way the ocean continues to influence the climate is through accompanying increases in water vapor in the atmosphere that leads to the damaging increases in extremes in the hydrological cycle.  Water vapor is also a powerful greenhouse gas and increased heating leads to drying and risk of drought and wildfire.  But it also fuels storms of all sorts and leads to risk of flooding.  That includes hurricanes and typhoons.” Said Dr. Kevin Trenberth, a senior scientist at National Center for Atmospheric Research, USA, another member of the team.

For example, over the past 12 months, a staggering 104 countries have recorded their hottest temperatures ever. Droughts, heat waves, floods, and wildfires have impacted Africa, Southern Asia, the Philippines, Brazil, Europe, the USA, Chile, and the Great Barrier Reef, as just but a few examples. Since 1980 for example, climate disasters have cost the USA nearly $3 trillion.

The heat in the ocean is the best measurement for monitoring the changing climate. “The ocean is our sentinel for planetary warming, acting as the major sink of surplus heat accumulating in Earth climate system as a result of anthropogenic emissions” said Dr. Karina von Schuckmann at Mercator Ocean International, coauthor of the study. If there continues to be a failure to take action to slow climate change, the disruption, unprecedented change and its implications, costs and loss and damages will continue to increase.

Ocean heat content changes for the upper 2000 meters of ocean waters, since 1958. Green bars indicate the measurement accuracy.

Ocean warming patterns for 2024 

The ocean warming patterns are not uniform; regional variations can be substantial.

The ocean surface temperature is also setting records.

Credit

Cheng et al.

Journal

Advances in Atmospheric Sciences

DOI

10.1007/s00376-025-4541-3 

Article Title

Sea Surface Temperatures and Deeper Water Temperatures Reached a New Record High in 2024

Article Publication Date

10-Jan-2025

 

Chimpanzees are genetically adapted to local habitats and infections such as malaria

Peer-Reviewed Publication

University College London

 

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Mother and baby chimpanzee in Uganda

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Credit: Kevin Langergraber: The Ngogo Chimpanzee Project

Chimpanzees bear genetic adaptations that help them thrive in their different forest and savannah habitats, some of which may protect against malaria, according to a study by an international team led by UCL researchers.

Chimpanzees are our closest living relatives, sharing over 98% of their DNA with humans, and the scientists say that their findings, published in Science, can not only teach us about our own evolutionary history, but also about the biology of malaria infection in humans.

Chimpanzees are endangered due to habitat destruction, poaching and infectious disease. The results of this study could also inform conservation as they suggest that climate and land use changes will likely have different impacts on different chimpanzee groups.

Lead author Professor Aida Andrés (UCL Genetics Institute) said: “There are just a few hundred thousand chimpanzees alive, but they are found across very different landscapes from east Africa to the far west of the continent, including dense tropical rainforests and open areas of woodland and savannah. This makes them quite unique, because except for humans, all other apes live exclusively in forests.

“Here we have shown that besides acquiring behavioural adaptations, different chimpanzee populations have evolved genetic differences to survive in their different local habitats.

“As chimpanzees are facing threats across their range, including environmental changes to the climate and displacement due to human pressures, it is important that their genetic diversity is conserved to maintain their resilience and ensure the long-term survival of this intelligent and fascinating species.”

To study genetic adaptation, the international team of researchers, from institutions across Africa, Europe and North America, needed to obtain DNA from the endangered and highly elusive wild chimpanzees without disturbing them. To do so, they used faecal samples that were collected as part of the Pan African Programme: The Cultured Chimpanzee (PanAf). State-of-the-art laboratory and computational methods enabled the scientists to study the chimpanzee DNA in these samples and perform the largest study of local adaptation in wild endangered mammals to date.

The researchers analysed the exomes (the protein-coding part of the genome) from 828 wild chimpanzees, 388 of which were included in the final analysis, representing 30 different populations of chimpanzees across the geographic and ecological range of the four chimpanzee subspecies. The scientists compared the genetic information to data about the local environment each chimpanzee population lives in, identifying genetic variants that stand out as being much more frequent in certain regions than others, and that likely confer a benefit to those carrying the genetic variant in particular habitats.

The scientists found evidence of genetic adaptation in genes related to certain pathogens (disease-causing microorganisms) among the chimpanzees living in forests, where there is a high concentration of pathogens, with the strongest evidence found in genes linked to malaria. This includes two genes that are also known to be responsible for adaptation and resistance to malaria in humans: GYPA and HBB, the latter being responsible for sickle cell anaemia in humans.

The findings suggest that malaria is likely a significant disease for wild forest chimpanzees and that adaptation to the malaria parasite has happened, independently, through changes in the very same genes in chimpanzees and humans.

First author Dr Harrison Ostridge (UCL Genetics Institute) said: “The close genetic similarities between the great apes have resulted in diseases jumping from apes to humans, such as with malaria and HIV/AIDS, so studying wild chimpanzees is extremely useful to understand these and other shared infectious diseases in humans, and could help to develop new treatments or vaccines.

“Finding evidence of adaptation to malaria in chimpanzees linked to the same genes that affect malaria resistance in humans is striking from an evolutionary point of view, as it suggests there may be limited ways that we can evolve resistance to the malaria parasite.”

The study suggests that chimpanzees have also adapted to their savannah habitats, which have higher temperatures, lower rainfall and less food availability. This shows that studying savannah chimpanzees may shed light on how human ancestors adapted to similar habitats millions of years ago, when they first moved from the African forest to the savannah.

Co-author and PanAf co-director Dr Hjalmar Kuehl (Senckenberg Museum of Natural History, Germany) commented: “This ground-breaking study on chimpanzee local adaptations could not be accomplished without the extraordinary collaboration of an international team of scientists who worked tirelessly to collect non-invasive data, including faecal samples, from countries across the chimpanzee range."

Co-author and PanAf co-director Dr Mimi Arandjelovic (Max Planck Institute for Evolutionary Anthropology, Germany) added: “We further welcome everyone interested in our research to contribute as community scientists at ChimpandSee.org, where one can help annotate videos collected alongside the genetic samples from across the chimpanzee range."

Male chimpanzee in Uganda

Credit

Kevin Langergraber: The Ngogo Chimpanzee Project

Chimpanzee in Tanzania

Credit

Carolyn Fryns, GMERC

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Journal

Science

DOI

10.1126/science.adn7954 

Article Title

Local genetic adaptation to habitat in wild chimpanzees

Article Publication Date

10-Jan-2025

 

A fast-moving belly flop: Researchers unveil the unique skills of cricket frogs

Virginia Tech

 

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Graduate researcher Talia Weiss observes a cricket frog.

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Credit: Photo courtesy of Jake Socha.

Is walking on water possible for frogs?

Several species have fascinated observers with their abilities to skip side-to-side and leap into the air from the surface of a pond as if the water were land. One such breed native to Virginia and North Carolina is the cricket frog. The way these frogs move in the water could bring insights to tools for the future of robotics, watercraft, and more.

Jake Socha, the Samuel Herrick Professor in Mechanical Engineering, leads a research team that studies the cricket frog’s unique ability to “skitter,” another name for jumping multiple times in succession. The team's findings were published in the Journal of Experimental Biology, with graduate researcher Talia Weiss serving as first author.

“Skittering is not actually a well-defined word for this behavior – one naturalist used it to describe a ‘jumping on water’ behavior in frogs in 1949, and since then, it’s been used for this type of locomotion in all the following literature,” Weiss said. “Part of this research is not only studying this behavior in cricket frogs, but to try and give ‘skittering’ a more precise, scientific definition.”

How do they do it? In their studies, Socha’s team members found that popular opinions generally state that the frog crosses the water without sinking, but doing so might still require a highly specialized anatomy. What does this frog have that other frogs don’t?

"Our lab has studied a range of animals, and many exhibit fascinating behaviors in navigating their environment," Socha said. "The humble cricket frog lives nearby, and yet it still surprised us with its cabilities, further motivating our curiosity to understand the living world.  

High-speed video for high-speed frogs

Cricket frogs are one of the smallest frogs in North America, easily sitting on the thumb of an average adult’s hand. To observe the cricket frog in motion, team members used high-speed videography. They recorded how the frog leaps on land as well as in the water, watching the movement of their legs as they navigated both.

The team found that the frogs actually sink with each jump. While “skittering” gives a picture of the frogs freely leaping about while only their feet penetrate the water’s surface, the recordings showed a different picture. Socha, Weiss, and their teammates saw that each time a frog came down from a leap, its entire body would submerge. The movement was less like a frog leaping and dancing across the water freely, and more like a plop and a jump. Their movements might more appropriately be called, “porpoising,” after the movement that a porpoise or dolphin uses: leaping into the air from beneath the surface of the water.

Launching from underwater

The reason that cricket frogs have previously appeared to dance across the water when viewed by eye is largely because of their rapid motion.

To record this ultra-fast motion, the team used a 20-gallon glass tank and released the frogs into it. High speed cameras shooting up to 500 frames per second were aimed from the side of the glass tank to capture the action above and below the water’s surface. As the frogs leapt, the team captured their getaway.

The footage was then slowed down to a small fraction of the original speed. When they watched the footage, team members made their surprising observation: The frogs did indeed sink.

“It’s fascinating how easily we can be fooled by fast animal movements,” said Socha. “Here, we’re fooled by a frog that appears like a skipping stone, but is actually jumping and dunking multiple times in a row. Frogs are great jumpers, but most of them don’t exhibit this porpoising behavior, and we still don’t know why. Is there something special about the frog’s leap, or is it simply a matter of small body size?”

By observing them in slow motion, team members could observe the motion of the frog as it retracted and extended its limbs. They also noticed that the angle of its body to the waterline played a factor, giving it the ability to balance itself in the water. They broke each jump cycle down to:

• Takeoff, from a submerged position
• Aerial, or time in the air following a jump
• Re-entry, back into the water
• Recovery, resetting for the next jump

In a little more than a single second, the frog would take off while completely submerged, extending its feet in an underwater push to propel its body above the surface. Its rear legs stayed extended while moving through the air, and its front legs moved from pressing against its body to reach forward. The extended front legs are the first to hit the water upon re-entry, and the back legs are still extended as it sinks. As it sinks, the back legs retract and bend back into a leaping position. Another jump is executed, repeating the movement.

It's basically a belly flop.

The team observed frogs doing as many as eight jumps in a row, each being fully executed in less than a second.

Understanding skittering is an important discovery for the realm of biology, but it holds other keys as well. This discovery provides a new physical basis for the future of bio-inspired robotics. It could be applied to a water testing system that is needed to be rapidly deployed, or an amphibious drone taking water depth measurements. Those futuristic devices can take cues from nature to use well-tested methods that frogs have been using for centuries.

 

Original study: DOI: 10.1242/jeb.249403

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Journal

Journal of Experimental Biology

Article Title

Skittering locomotion in cricket frogs: a form of porpoising Icon for The Forest of Biologists