Thursday, March 11, 2021

Paper: Personal charitable donation budgets flexible in aftermath of deadly storms

UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN, NEWS BUREAU

Research News

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IMAGE: NEW RESEARCH CO-WRITTEN BY UNIVERSITY OF ILLINOIS URBANA-CHAMPAIGN EXPERTS TATYANA DERYUGINA AND BENJAMIN M. MARX FINDS THAT CHARITABLE GIVING IN THE AFTERMATH OF CATASTROPHIC TORNADOES DOESN'T NECESSARILY CROWD OUT DONATIONS... view more 

CREDIT: PHOTO BY L. BRIAN STAUFFER

CHAMPAIGN, Ill. -- Charitable donations account for about 2% of gross domestic product in the U.S., but it's not well-understood whether an event such as a deadly storm inspires increases in charitable giving or simply reallocates a fixed supply of donation dollars that would have otherwise gone to another cause.

A new paper from a team of University of Illinois Urbana-Champaign experts finds that, in the aftermath of catastrophic tornadoes, charitable giving to alleviate an unanticipated event doesn't necessarily crowd out monetary donations to other causes.

Research co-written by Tatyana Deryugina and Benjamin M. Marx uses comprehensive annual tax return data to estimate whether discrete but destructive events such as fatal tornadoes increase total charitable giving.

The paper, which will be published in the journal American Economic Review: Insights, finds that each tornado fatality increases total donations from individuals living nearby by almost $2 million.

"There is an active debate in the research on charitable giving on the extent of donor substitution between charitable causes," said Deryugina, a professor of finance at Illinois. "By employing a natural experiment with both geographic and temporal variation as well as datasets that contain the majority of dollars donated across the U.S., our paper can rule out the possibility that individuals choose a set amount to donate to charity and then apportion that amount among charities."

The researchers measured charitable giving from 2002-17 using ZIP code-level individual income tax data from the Internal Revenue Service, which reports all income tax deductions claimed for donations to any registered charity.

By combining the IRS data with geospatial information on the incidence of tornadoes, the researchers were able to zero in on the destruction wrought by lethal tornadoes, allowing them to identify events that affected populated areas and caused tens of millions of dollars' worth of damage.

"We looked at tornadoes because they hit a very specific and limited area, which gives us a treatment area and a clean control area so we can get better estimates via comparison," said Marx, a professor of economics at Illinois.

Deryugina and Marx found that lethal tornadoes significantly increased total charitable donations from individuals living at least 20 miles away in the same state from a tornado's path by almost $2 million per fatality.

"We excluded ZIP codes that were within 20 miles of the tornado's path, so we weren't looking at the places that were directly affected by property damage or loss of life," Marx said. "We went outside of that 20-mile ring and out to the rest of the state to estimate the effect on average giving in those other ZIP codes. And if you add up those effects across all of those ZIP codes, you arrive at a total state-level effect, which is where the $2 million figure comes from."

Because total giving increases, the scholars were able to rule out perfect substitution between charitable causes and conclude that the supply of donations from an "altruism budget" can expand given exigent circumstances, Deryugina said.

"We can't rule out that there's some marginal crowding-out effects, because we just find that total giving goes up, but I'm comfortable speculating that there's not a lot of substitution because the total increase is fairly large," she said. "If there is some substitution, it's not huge. Basically, we see no evidence for the existence of a radical pullback in charitable giving to other causes after these natural disasters."

Using annual tax return data from charities, the researchers also found that there were no significant negative effects on charities in the locations from which increased donations to fatal tornadoes originated.

"That implies that giving in response to new needs doesn't come at the expense of these other causes," Marx said.

Charitable giving for natural disasters is common, with a nationally representative survey indicating that about 30% of U.S. households donated money in 2017-18. While the data in the paper covered the majority of dollars donated, it may not be representative of lower-income households, whose charitable donation budget may be more fixed, the researchers said.

"We only had aggregate, ZIP code-level data. We would have loved to break it down by income group, but we just didn't have the data," Deryugina said. "We do note in the paper that most charitable giving in the U.S. is by wealthier people. Lower-income individuals and households are less likely to file taxes, and all of our data came from the IRS. So our estimates are representative of individuals who filed a tax return, but those individuals make up a sizable share of total charitable giving."

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The research was supported by the Lilly Family School of Philanthropy.

Climate change may not expand drylands

New analysis highlights uncertainty about the future state of drylands

HARVARD JOHN A. PAULSON SCHOOL OF ENGINEERING AND APPLIED SCIENCES

Research News

Previous studies used atmospheric information, including rainfall and temperature, to make projections about future land conditions. The real picture is more complicated than that, said Kaighin McColl, Assistant Professor of Earth and Planetary Sciences and of Environmental Science and Engineering at SEAS and senior author of the paper.

"Historically, we have relatively good records of rainfall and temperature but really poor records of the land surface, things like soil moisture and vegetation," said McColl. "As a result, previous definitions of drylands are based only on how the atmosphere is behaving, as an approximation of the land surface. But models can now simulate both atmospheric and land conditions. By just looking directly at the land surface in climate models, we find that the models aren't showing a clear increase of drylands over time and that there is huge uncertainty about the global average state of drylands in the future."

The research is published in Nature Climate Change.

"If you want to know if the land is going to get drier, if crops are going to fail or if a forest is going to dry out, you have look at the land itself," said Alexis Berg, a research associate in McColl's lab and first author of the paper. "How much vegetation is there? Are the plants water stressed?"

While climate models have historically focused on the atmosphere, modern climate models now also simulate vegetation behavior and land hydrology.

For example, when plants absorb CO2, they lose water. If there is more CO2 in the air, plants can release less water and become more water efficient. More CO2 also results in more fertilizer for plants, which helps them grow and reduces water stress.

These effects have long been known, but previous atmospheric-only indicators of drylands just weren't capturing these land surface effects.

"As the climate is warming, there is a divergence between atmospheric and land surface behavior," said Berg.

To account for that divergence, McColl and Berg developed a new metric of drylands, based on land surface properties, including biological responses to higher atmospheric CO2, and compared drylands projections to those derived solely from atmospheric metrics.

"Our research shows that while some drylands may expand, climate models don't project that there will be a dramatic and rapid global expansion of drylands," said McColl.

However, simulating complex land processes remains challenging in global models.

"There is still a lot of uncertainty about how vegetation and the water cycle will change in a warming world," said McColl.

McColl and his team aim to reduce that uncertainty in future research by developing more accurate land surface models.

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This research was supported in part by a Winokur Seed Grant in Environmental Sciences from the Harvard University Center for the Environment.

Global battle against antibiotic resistance requires tailored solutions

RADBOUD UNIVERSITY MEDICAL CENTER

Research News

The global battle against antibiotic resistance can only succeed if local contexts are taken into account. "A tailored approach is needed in each country," says Heiman Wertheim of Radboud university medical center. "There is no "one-size-fits-all' solution." This was the main finding of a study on antibiotic resistance in African and Asian countries funded by the British Wellcome Trust. Wertheim is the lead investigator of a large group of international researchers who recently published an article on this study in The Lancet Global Health.

Antibiotics are powerful treatments for bacterial infections. They are indispensable for controlling infections such as pneumonia, meningitis, or blood poisoning (sepsis) caused by bacteria. But they are ineffective for treating viral infections, such as colds or flu, and do not work against infections with parasites, fungi or yeasts either.

Increasing resistance

Incorrect use of antibiotics increases the risk of antibiotic resistance. This means that bacteria adapt in such a way that the antibiotic is no longer effective and the disease can no longer be controlled. Antibiotic resistance is now a major problem worldwide.

The problem is growing especially in Low- and Middle-income Countries (LMIC), where antibiotic use increased by 35 percent between 2000 and 2010. Research in various countries show that for example 80 percent of children under the age of five with respiratory infections are treated with antibiotics. In many cases, this was unjustified. To gain more insight into this problem, a large group of international researchers led by Heiman Wertheim from Radboud university medical center carried out the ABACUS project. ABACUS stands for AntiBiotic ACces and USe.

Large differences between countries

The results of the study, which was conducted in LMIC countries in Africa (Mozambique, Ghana, South Africa) and Asia (Bangladesh, Vietnam, Thailand), have now been published in The Lancet Global Health. Wertheim: "We looked primarily at how easy or difficult it is to obtain antibiotics in those countries and in which situations they are used. On those aspects alone, we found enormous differences between the six countries. For example, in some countries you can purchase antibiotics in the pharmacy only with a doctor's prescription, while in others there are no restrictions and antibiotics are available at any time from the drug store around the corner. We also saw that antibiotics are much more readily available in Asia than in Africa. And that the situation is relatively better in wealthier countries such as Thailand and South Africa."

Self-medication

Nga Thi Thuy Do, a researcher at the Oxford University Clinical Research Unit in Vietnam and lead author of the paper, summarizes the findings as follows: "Bangladesh and Vietnam have the most places where antibiotics can be purchased without a prescription. In some settings you have one drugseller per 500 inhabitants, which is an awful lot. This is reflected in the extent to which antibiotics are used as self-medication. In Vietnam, Bangladesh and Ghana, 57 percent, 45 percent and 36 percent of the population, respectively, regularly take antibiotics for self-medication. But self-medication is much less frequent in Mozambique, Thailand and South Africa, with rates of 8 percent, 4 percent and 1 percent, respectively. The difference is enormous."

The researchers also observed quite some uncertainty in the local population - even among the sellers of antibiotics - about what an antibiotic actually is and how you can recognize it. For example, painkillers were sometimes confused with antibiotics. In a follow-up study, also funded by the Wellcome Trust, the consortium will investigate whether improved recognition of antibiotics can lead to better use.

Context, context, context

The reasons for opting for self-medication are obvious: getting antibiotics from the drugstore without a prescription is faster, cheaper and easier. But purchasing antibiotics without a prescription is not always possible. And that in turn depends on all kinds of factors such as how the healthcare is organized, whether consumers trust the supplier and the severity of the disease. Wertheim: "Our research makes it clear that a generic approach towards combating antibiotic resistance is ineffective. To have any chance of success, you must consider the context that affects the availability and use of antibiotics in each country. The conclusions of our study provide an excellent starting point for giving shape to global initiatives to improve antibiotic use, so that those who really need it can get the right antibiotic and those with a runny nose can get a 'warm cup of tea'."

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https://www.thelancet.com/journals/langlo/article/PIIS2214-109X(21)00024-3/fulltext

Deforestation favors an increase in the diversity of antibiotic-resistant soil bacteria

Study analyzed some 800 million DNA sequences extracted from 48 soil samples collected in Pará State and northern Mato Grosso State, both of which are part of the Amazon biome

FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO

Research News

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IMAGE: STUDY SUGGESTS THAT REPLACING NATIVE VEGETATION WITH PASTURE OR CROPS INCREASES COMPETITION AMONG MICROORGANISMS, FAVORING THOSE WITH ANTIMICROBIAL RESISTANCE GENES view more 

CREDIT: CENA-USP

In Brazil, a study conducted by researchers affiliated with the University of São Paulo (USP) and collaborators showed that deforestation in the Amazon causes an increase in the diversity of antibiotic-resistant bacteria. An article on the study, published in Soil Biology and Biochemistry, compares the microorganisms that live in the soil of native forest with those found in pasture and croplands. The researchers found a far larger number of genes considered markers of antibiotic resistance in deforested than forested areas.

“Bacteria produce substances with which to attack each other in a competition for resources that’s usual in any environment. When an area is deforested, however, several factors intensify this competition, favoring the bacteria that can resist these substances. If they reach humans, these microorganisms can become a major problem,” said Lucas William Mendes, a researcher supported by FAPESP at USP’s Center for Nuclear Energy in Agriculture (CENA) in Piracicaba, in the state of São Paulo, and last author of the article.

The study was part of a project linked to the FAPESP Research Program on Biodiversity Characterization, Conservation, Restoration and Sustainable Use (BIOTA-FAPESP) and led by Tsai Siu Mui, a professor at CENA-USP.

Antibiotic resistance is a global public health emergency, according to the World Health Organization (WHO), which says drug-resistant diseases cause some 700,000 deaths per year worldwide.

In the study, the researchers at CENA-USP, collaborating with colleagues at the Luiz de Queiroz College of Agriculture (ESALQ-USP) and scientists at the National Laboratory for Scientific Computing in Petrópolis, Rio de Janeiro State, analyzed some 800 million DNA sequences extracted from 48 soil samples collected in Pará State and northern Mato Grosso State, both of which are part of the Amazon biome.

Using bioinformatics tools, the researchers ran the DNA sequences from the samples against a genetic database and found 145 antibiotic-resistant genes that trigger 21 different molecular mechanisms. Although antibiotic-resistant bacteria are present in forest soil, these microorganisms and their resistance mechanisms are much more abundant in the soil of pasture, deforested areas, and croplands.

Deforestation microorganisms

“The process of occupation in the Amazon consists of first logging the most valuable trees and then clearing and burning all the rest to make way for crops or forage grass for cattle,” Mendes said. “Besides ash from the burned vegetation, the soil is limed to reduce the acidity and other agrochemicals are applied. The abundance of nutrients fuels bacterial proliferation and fierce competition for resources.”

Previous studies by the CENA-USP group showed that despite the reduction in forest soil microorganism diversity, the abundance of bacteria benefited plants by nutrient cycling and augmented photosynthesis, and also had positive effects on the atmosphere, including carbon fixation and consumption of methane, the second most important greenhouse gas after carbon dioxide.

In the latest study, the researchers were struck by the large quantity of bacteria that were resistant to two specific classes of antibiotics, tetracyclines and beta-lactamases. Medications with these active ingredients are widely used to treat cattle diseases and can reach the soil via feces and urine since absorption of antibiotics in cattle is low. Furthermore, the use of livestock manure as fertilizer can contribute to the spread of drug-resistant bacteria, according to the researchers.

Scientists cannot be sure that microorganisms immune to antibiotics are capable of migrating from the soil of the Amazon to food produced there, such as grain, sugarcane, and beef. “Some research assumes the transfer can occur, but to date, no studies have demonstrated it,” Mendes said. “It needs to be watched carefully because if these drug-resistant bacteria reach humans, they’ll cause a serious public health problem.”

Nor are there any immediate solutions to prevent bacteria from multiplying in cultivated soil. Management techniques that take into account other functions of microorganisms besides boosting crop yield, such as nutrient cycling and reducing species that produce methane, for example, could help mitigate the problem.

This can be done by transplanting natural soil to a cultivated area or using inoculants, microorganism-based products that perform important functions in the soil and also reduce the need for fertilizer and agrochemicals. Indeed, the market for microbiome-based agricultural products is expected to be worth more than 10 billion US dollars by 2025 (read more at: agencia.fapesp.br/34195).

In the Amazon, solutions and opportunities may be very near a pasture or plantation, in the soil of the native forest.

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About São Paulo Research Foundation (FAPESP)

The São Paulo Research Foundation (FAPESP) is a public institution with the mission of supporting scientific research in all fields of knowledge by awarding scholarships, fellowships and grants to investigators linked with higher education and research institutions in the State of São Paulo, Brazil. FAPESP is aware that the very best research can only be done by working with the best researchers internationally. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration. You can learn more about FAPESP at http://www.fapesp.br/en and visit FAPESP news agency at http://www.agencia.fapesp.br/en to keep updated with the latest scientific breakthroughs FAPESP helps achieve through its many programs, awards and research centers. You may also subscribe to FAPESP news agency at http://agencia.fapesp.br/subscribe.

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.

 

Whooping cranes steer clear of wind turbines when selecting stopover sites

Proliferation of wind-energy infrastructure across the Great Plains has created obstacles along key migration routes; future developers could place infrastructure outside of migration corridors to avert negative impacts

THEY SUMMER IN LETHBRIDGE. ALBERTA WHICH IS ALSO HOME TO WIND TURBINES


ECOLOGICAL SOCIETY OF AMERICA

Research News

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IMAGE: A PAIR OF WHOOPING CRANES WALKING ALONG THE EDGE OF A WETLAND IN CENTRAL KANSAS view more 

CREDIT: TRAVIS WOOTEN/USGS

As gatherings to observe whooping cranes join the ranks of online-only events this year, a new study offers insight into how the endangered bird is faring on a landscape increasingly dotted with wind turbines. The paper, published this week in Ecological Applications, reports that whooping cranes migrating through the U.S. Great Plains avoid "rest stop" sites that are within 5 km of wind-energy infrastructure.

Avoidance of wind turbines can decrease collision mortality for birds, but can also make it more difficult and time-consuming for migrating flocks to find safe and suitable rest and refueling locations. The study's insights into migratory behavior could improve future siting decisions as wind energy infrastructure continues to expand.

"In the past, federal agencies had thought of impacts related to wind energy primarily associated with collision risks," said Aaron Pearse, the paper's first author and a research wildlife biologist for the U.S. Geological Survey's Northern Prairie Wildlife Research Center in Jamestown, N.D. "I think this research changes that paradigm to a greater focus on potential impacts to important migration habitats."

The study tracked whooping cranes migrating across the Great Plains, a region that encompasses a mosaic of croplands, grasslands and wetlands. The region has seen a rapid proliferation of wind energy infrastructure in recent years: in 2010, there were 2,215 wind towers within the whooping crane migration corridor that the study focused on; by 2016, when the study ended, there were 7,622 wind towers within the same area.

Pearse and his colleagues found that whooping cranes migrating across the study area in 2010 and 2016 were 20 times more likely to select "rest stop" locations at least 5 km away from wind turbines than those closer to turbines.

The authors estimated that 5% of high-quality stopover habitat in the study area was affected by presence of wind towers. Siting wind infrastructure outside of whooping cranes' migration corridor would reduce the risk of further habitat loss not only for whooping cranes, but also for millions of other birds that use the same land for breeding, migration, and wintering habitat.

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The Ecological Society of America, founded in 1915, is the world's largest community of professional ecologists and a trusted source of ecological knowledge, committed to advancing the understanding of life on Earth. The 9,000 member Society publishes five journals and a membership bulletin and broadly shares ecological information through policy, media outreach, and education initiatives. The Society's Annual Meeting attracts 4,000 attendees and features the most recent advances in ecological science. Visit the ESA website at https://www.esa.org.


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A whooping crane (Grus americana) family in their wintering grounds at Aransas National Wildlife Refuge in Texas.

CREDIT

Klaus Nigge/USFWS

Birds learn to avoid flashy, hard-to-catch butterflies and their lookalikes

FLORIDA MUSEUM OF NATURAL HISTORY

Research News

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IMAGE: RESEARCH SUGGESTS SHOWY COLORS AND PATTERNS IN CERTAIN BUTTERFLIES COULD WARN PREDATORS OF THEIR SPEED AND AGILITY. IN ADELPHA BUTTERFLIES, MANY DISTANTLY RELATED SPECIES HAVE ONE OF THREE COMMON "RACING... view more 

CREDIT: JEFF GAGE/FLORIDA MUSEUM OF NATURAL HISTORY

GAINESVILLE, Fla. --- The showy colors of some butterflies could advertise their speed and nimbleness, much like a coat of bright yellow paint on a sports car. A new study shows birds can learn to recognize these visual cues, avoiding not only butterflies they've failed to nab in the past but similar-looking species as well.

The research provides some of the strongest evidence to date for the idea of evasive mimicry, a strategy in which animals protect themselves from predators by matching the colors or patterns of agile relatives. First proposed more than 60 years ago, the hypothesis has been a challenge to test.

But in an experimental setting, researchers found that wild birds learned and remembered the wing patterns of artificial butterflies that evaded their attacks, as well as those that had a foul flavor, equally spurning both in follow-up tests and often ignoring lookalikes with similar color patterns. Unexpectedly, the birds learned to avoid evasive butterflies faster than distasteful ones.

The results suggest that being hard to catch may deter predators at least as effectively as chemical defenses.

"There's a common idea that being distasteful is one of the best kinds of defense to have, but at least in this experiment, that didn't prove to be the case," said study co-author Keith Willmott, curator and director of the Florida Museum of Natural History's McGuire Center for Lepidoptera and Biodiversity.

Most research on warning coloration has focused on species with chemical defenses and those that mimic them. Monarch butterflies, for example, sport bright wing patterns of black lines on a field of orange, indicating they contain bad-tasting toxins. A predator that eats one will likely avoid both monarchs and the similar-looking viceroy butterfly in the future.

But a growing number of studies suggest a flashy exterior can mean something entirely different: that an animal is quick. Predators learn to associate these kinds of patterns with a futile chase that leaves them hungry, and species that evolve imitations of these "racing stripes" can capitalize on a defensive strategy while reinforcing the visual message.

"When many species share the same color pattern, they're better able to educate predators to avoid them," Willmott said. "The more species that share it, the better."

During his Ph.D. studies, Willmott worked on the classification of a group of fast-flying tropical butterflies known as Adelpha. At first, he found them nearly impossible to identify. It seemed the genus either contained only a few species with slight variations in wing pattern or dozens of species that looked virtually the same. The latter turned out to be the case, with more than 90 species making up the group. Like some researchers before him, Willmott began to wonder whether evasive mimicry could explain why so many species of Adelpha looked alike.

"It was always mysterious to me," he said. "Species whose upper wings looked incredibly similar were distantly related, and we started to see cases where even subspecies of multiple species suddenly developed very unique color patterns. Really, the only way you can explain that is through mimicry."

While other researchers suggested some Adelpha must have hidden chemical defenses, the explanation didn't quite satisfy Willmott. Toxic butterflies are usually slow fliers with long wings and a propensity for playing dead when caught. Adelpha butterflies, however, don't display these traits, having instead a short, stout thorax and smaller, triangular wings - characteristics that enable fast, erratic flight and sharp turns.

But he wasn't sure how to test this hypothesis until a conversation with fellow researchers at a 2018 conference in India: Johanna Mappes was an expert at developing predator-prey experiments with wild birds; Pável Matos-Maraví was interested in the evasive behavior of skipper butterflies; and Marianne Elias and her Ph.D. student Erika Páez were eager to study what drove the evolution of wing color patterns in the genus Adelpha, including the possible effects of predators.

Simulating how evasive mimicry might play out in the wild appealed to the group. The ability of prey to escape predators' attacks has been "virtually unstudied," said Elias, a research group leader at the Institute of Systematics, Evolution, Biodiversity at the National Museum of Natural History in France.



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Because many species in the genus Adelpha look alike from the top, researchers often use their intricately patterned undersides to distinguish them. From left, these butterflies are Adelpha salmoneus, Adelpha cocala and Adelpha epione.

CREDIT

Jeff Gage/Florida Museum of Natural History

Previous work had shown birds can identify the visual cues of evasive prey. Together, the team designed an experiment to test whether potential examples of evasive mimicry in Adelpha could be the result of natural selection.

At a special facility in Finland, the researchers collaborated with Janne Valkonen of the University of Jyväskylä to capture wild blue tits, birds that would never have encountered tropical Adelpha butterflies, and train them to catch a paper butterfly with an almond treat attached to its underside. Then, the birds were presented with a plain brown paper butterfly as a control and a paper butterfly with one of three common Adelpha wing patterns: a vertical white band on black forewings, a vertical orange band on black forewings or a combination of orange-striped forewings with white-striped hindwings.

The paper Adelpha butterfly either concealed an almond soaked in a bitter substance - a proxy for chemical defense - or evaded the bird's attack by gliding away on a rail. The birds learned to connect a particular wing pattern with the negative experience of distastefulness or escape, eventually avoiding this butterfly and striking the control instead. In a final test, they were given four butterflies at the same time: the plain brown butterfly and all three Adelpha butterflies, including one with the pattern they had seen before.

They strongly avoided the butterfly they had learned to associate with the bitter almond or fast flight and often avoided butterflies that shared a similar color or pattern.

Birds were 1.6 times more likely to attack the distasteful butterfly than evasive ones, perhaps because they had varying levels of tolerance for the bad-tasting almond, said Páez, who co-led the study with Valkonen. After all, even a bitter morsel of food is better than nothing.

"Bad-tasting prey could provide a nutritive meal whereas missing prey completely cannot," she said.

While birds tend to avoid colorful prey by default, the study provides evidence of learned behavior, Willmott said.

"This potentially explains many cases of apparent mimicry that lacked evidence of chemical defense."

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Matos-Maraví of the Biology Centre, Czech Academy of Sciences, and Mappes of the University of Jyväskylä and the University of Helsinki also co-authored the study.



CAPTION

Researchers trained wild birds to attack paper butterflies with an almond treat attached to the underside, bottom left. They then gave birds a plain brown butterfly, center, and a striped butterfly that was either hard to catch or concealed a bitter almond. Birds eventually avoided the evasive and distasteful prey.

CREDIT

Erika Páez

 

CLOAKING DEVICE

Optimal design for acoustic unobservability in water

SHINSHU UNIVERSITY

Research News

Until now, it was only possible to optimize an acoustic cloaking structure for the air-environment. However, with this latest research, Acoustic cloak designed by topology optimization for acoustic-elastic coupled systems, published in the latest Applied Physics Letters, it is possible to design an acoustic cloak for underwater environments.

In the conventional topology optimization of acoustic cloaking, the design method was based on an analysis that approximated an elastic body in the air as a rigid body. However, since the approximation holds only for materials that are sufficiently stiff and dense such as metal in the air, there were few material options other than metal. Moreover, it was impossible to design an acoustic cloak in water by the approximation method.

In this study led by Garuda Fujii of Shinshu University, the group developed topology optimization based on the finite element analysis of coupled acoustic-elastic wave propagation. By considering the interaction between the vibration of the elastic body and the sound wave in the optimization calculation, it is now possible to select the material that constitutes the acoustic cloak from light ABS and other materials and to design the acoustic cloak for use in air and water. Furthermore, the group successfully designed wide frequency band acoustic cloaks optimized respectively for each environment, aerial and underwater.

This novel research has made it possible to select the constituent materials of the acoustic cloak and the surrounding acoustic medium environment (air or underwater) with a high degree of functionality. It is expected that the functions of acoustic cloaking will be greatly expanded.

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For more information on Associate Professor Garuda Fujii: http://www.kankyo.shinshu-u.ac.jp/~garudalab/html/index_en.html