A new social role for echolocation in bats that hunt together

Date: June 19, 2020

Source: Smithsonian Tropical Research Institute

Searching for food at night can be tricky. To find prey in the dark, bats use echolocation, their "sixth sense." But to find food faster, some species, like Molossus molossus, may search within hearing distance of their echolocating group members, sharing information about where food patches are located. Social information encoded in their echolocation calls may facilitate this foraging strategy, according to a recent study by Smithsonian Tropical Research Institute (STRI) scientists and collaborating institutions published online in Behavioral Ecology.

Previous research has identified several ways in which echolocation can transfer social information in bats. For example, "feeding buzzes," the echolocation calls bats produce to home in on prey they've spotted, can serve as cues of prey presence to nearby eavesdropping bats. On the other hand, echolocation calls that bats produce while looking for food, called "search-phase" calls, were not known to transfer social information.

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Bats depend on teamwork when foraging over farmland

MARCH 26, 2020

by Forschungsverbund Berlin e.V. (FVB)

Scientists from the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) have reported in a paper published in the journal Oikos that bats forage on their own in insect-rich forests, but hunt collectively in groups over insect-poor farmland. They seem to zoom in on places where conspecifics emit echolocations during the capture of insects, an inadvertent clue that reveals high-yielding areas to others. However, "listening" to their hunting companions to find food only works when sufficient numbers of bats forage in the same area. If numbers continue to decline, density could fall below a critical level and joint hunting could become difficult or impossible. This could pose an additional threat to the survival of species such as the Common noctule.

Human activities have massively changed the Earth over centuries. While Central Europe was covered by dense primeval forests in ancient times, today, farmland, meadows and managed forests dominate the countryside. Humans have transformed natural landscapes into cultural landscapes and many wild animals disappeared, while others found new ecological niches. Bats were particularly successful in the latter process. As so-called cultural successors, many species were able to survive in modern environments, finding shelter in buildings and feeding above arable land and managed forests. But what is the secret of their success? Are they particularly efficient hunters?

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Coronavirus outbreak raises question: Why are bat viruses so deadly?

FEBRUARY 10, 2020

by Robert Sanders, University of California - Berkeley

It's no coincidence that some of the worst viral disease outbreaks in recent years—SARS, MERS, Ebola, Marburg and likely the newly arrived 2019-nCoV virus—originated in bats.

A new University of California, Berkeley, study finds that bats' fierce immune response to viruses could drive viruses to replicate faster, so that when they jump to mammals with average immune systems, such as humans, the viruses wreak deadly havoc.

Some bats—including those known to be the original source of human infections—have been shown to host immune systems that are perpetually primed to mount defenses against viruses. Viral infection in these bats leads to a swift response that walls the virus out of cells. While this may protect the bats from getting infected with high viral loads, it encourages these viruses to reproduce more quickly within a host before a defense can be mounted.

This makes bats a unique reservoir of rapidly reproducing and highly transmissible viruses. While the bats can tolerate viruses like these, when these bat viruses then move into animals that lack a fast-response immune system, the viruses quickly overwhelm their new hosts, leading to high fatality rates.

"Some bats are able to mount this robust antiviral response, but also balance it with an anti-inflammation response," said Cara Brook, a postdoctoral Miller Fellow at UC Berkeley and the first author of the study. "Our immune system would generate widespread inflammation if attempting this same antiviral strategy. But bats appear uniquely suited to avoiding the threat of immunopathology."

The researchers note that disrupting bat habitat appears to stress the animals and makes them shed even more virus in their saliva, urine and feces that can infect other animals.

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Bats live mostly out of sight and out of mind. But their falling numbers are a reason to look up and worry

NOVEMBER 5, 2019

by Patrick M. O'connell

Credit: CC0 Public Domain

It's the time of year when ghouls and goblins, mummies and monsters are out in force. But unlike many Halloween creatures, bats live in more than the imagination, making their homes in caves and hollowed-out trees in Illinois and the urban parks of Chicago.

The elusive winged mammals who make special appearances in decorations and throughout popular culture during the fall are under increasing threats across the state and the Midwest, the victim of a stubborn and spreading disease, shrinking natural habitat and a growing wind turbine industry. And with new changes to the Endangered Species Act, scientists and environmental advocates fear additional species of bats may be under siege from encroaching development and a changing, warming climate.

"It's really important to protect those remaining in the landscape so the bats do have a chance to reproduce," said Winifred Frick, the chief scientist at Bat Conservation International, adding that she believes it will be harder to prove that certain habitats are critical for the survival of a species in order for them to qualify for protected status in the future. "Anything that would hinder our ability to protect their habitat or their maternity habitats is less than ideal."

Mostly out of sight and out of mind because of their nighttime lifestyle and solitary flight tendencies, a dozen species of bats regularly call Illinois home, at least during the summer months, and the animals can be found throughout the Midwest. Aside from their rare nuisance appearances in attics, bats play a positive, critical role in the ecosystem, scientists say.

The animals can be found in a variety of places across the city and the suburbs, scientists said, including city parks, forest preserves, golf courses and under roof tiles. Bats benefit humans during the summer by eating pesky insects, including mosquitoes, and provide important protection for Midwestern crops like corn and soybeans by feasting on bugs that could otherwise ravage farmland. In addition to pest control, bats—there are more than 40 different species that live in the U.S. - help pollinate plants and disperse seeds. And contrary to popular myth, less than half of 1% of bats carry rabies, according to the U.S. Fish and Wildlife Service.

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Bats starving to death in Australia drought

SEPTEMBER 24, 2019

Large numbers of bats are being found severely emaciated or starved to death in Australia amid a prolonged drought that is crippling their food supply, according to wildlife carers and environment officials.

There has been a "rapid increase" in the number of stricken native flying foxes found in areas of Queensland and New South Wales over the past two weeks, rescue group Bats Queensland told AFP.

Volunteer wildlife carer Ashley Fraser said Tuesday that parts of the picturesque Gold Coast, a popular tourist destination, were currently "littered" with hundreds of dead bats.

Though there have been cases of mass bat starvation in the region before, Fraser said her organisation had never dealt with an event on this scale.

"We can expect to see it get worse as well," she told AFP.

"The changing climate is going to worsen the drought and make it a pretty poor environment for bats to try to survive in."

Some flying fox species are listed as vulnerable to extinction. They are also a key pollinator of eucalyptus trees, the koala's main food source.

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A deadly fungus is killing millions of bats in the U.S. Now it's in California

JULY 5, 2019

by Louis Sahagun, Los Angeles Times

A mysterious fungus that has killed millions of bats in the eastern United States and left caves littered with their tiny carcasses has arrived in Northern California and appears poised to spread throughout the state, according to officials.

Government biologists confirmed Friday that a number of bats found near Lassen Volcanic National Park had tested positive for the germ that causes white-nose syndrome—a relatively new disease that leaves a trademark smudge of white on the infected animal's muzzle.

The illness, which is caused by a cold-loving fungus, appeared suddenly in the Northeast just over a decade ago and has moved steadily west. The fungus has devastated North American bat species in some regions and pushed the natural pest controllers toward extinction.

According to California biologists, the fungus was detected in four bats found roosting within houses and a bank building in the town of Chester, about 15 miles southeast of the park. The first case was detected a year ago, and the others much more recently, officials said.

"We all thought we were going to have more time before it got this far west," said Winifred Frick, a UC Santa Cruz biologist and chief scientist with Bat Conservation International. "We should all be very concerned about this heartbreaking discovery."

Since it was first discovered in New York 12 years ago, the fungus has swept across 38 states, and killed legions of bats. A majority of the dead were little brown bats—one of the most common mammals in North America—but scientists say that most of the 45 species of bats in the U.S. and Canada may be susceptible to the disease. (The fungus is not known to cause illness in humans, according to officials.)

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Ear-generated Doppler shifts in bat biosonar

Date:  June 4, 2019

Source:  Virginia Tech

Anybody who has been passed by an ambulance at high speed has experienced a physical effect called the Doppler shift: As the ambulance moves toward the listener, its motion compresses the siren's sound waves and raises the sound pitch. As the ambulance moves away from the listener, the sound waves get dilated and the pitch is lowered. A listener wearing a blindfold could use this Doppler shift pattern to track the motion of the ambulance.

In a paper published by the Proceedings of the National Academy of Sciences, the authors, Rolf Mueller, professor of mechanical engineering in the College of Engineering, and his doctoral student, Xiaoyan Yin, demonstrate that the ears of bats come with a "built-in ambulance" that creates the same physical effect. Yin and Mueller think the study of ear-generated Doppler shifts in bat biosonar could give rise to new sensory principles that could enable small, yet powerful sensors. An example of this type of sensor would be for drones that can operate in dense foliage or autonomous underwater vehicles navigating near complex underwater structures.

"The animals move their ears fast enough so that sound waves that impinge on the ears are transformed by the motion of the ear surfaces and shifted to higher or lower frequencies," said Mueller. "In fact, the bat species studied (horseshoe bats and Old World Roundleaf bats) can move their ears so fast that Doppler shifts of around 350 Hz can be created. This is about seven times larger than the smallest Doppler shift the animals haven been shown to be able to detect."

Doppler shifts have long been known to play an important role in the biosonar system of bats such as the species studied by Mueller and Yin. The bats have the enviable ability to hunt in very dense vegetation, but to accomplish this, they have to solve the problem of how to distinguish a moth, their preferred prey, from hundreds of leaves that surround it.

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Holy Pleistocene Batman, the answer's in the cave

Let's say you wanted to solve a 20,000-year-old mystery, where would you start?

Date:  April 25, 2019

Source:  James Cook University

Let's say you wanted to solve a 20,000-year-old mystery, where would you start? Perhaps archaeology and geology come to mind. Or, you could sift through a 3-metre pile of bat faeces.

Researchers from James Cook University in Cairns, Australia, chose the bat poo in their quest to answer to a long-standing question: why is there some much biodiversity on the islands of Sumatra, Borneo and Java, when not so long ago (geologically speaking) they were all part of one vast continent?

One theory has been that the former continent (Sundaland) was dissected by a savanna corridor. "That might explain why Sumatra and Borneo each have their own species of orang-utan, even though they were linked by land for millions of years," Dr Chris Wurster said. "The corridor would have divided the two separate rainforest refuges, as the sea does now."

The corridor theory has been boosted by millions of insect-eating bats, which have gathered evidence about the landscape over millennia and deposited it in layers in their caves.

"Bat poo is highly informative, and especially so in the tropics, where the climate can make some of the more traditional modes of investigation less available," Dr Wurster said.

A three-metre pile of bat faeces at Salah Cave in Borneo gave the researchers a 40,000-year-old record composed of insect skeletons.

"We can't tell what insects the bats were eating throughout that time, because they're in tiny fragments, but we can read the chemistry," Dr Wurster said.

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How light from street lamps and trees influence the activity of urban bats

A complex relationship

Date:  March 27, 2019

Source:  Forschungsverbund Berlin

Artificial light is rightly considered a major social, cultural and economic achievement. Yet, artificial light at night is also said to pose a threat to biodiversity, especially affecting nocturnal species in metropolitan areas. It has become clear that the response by wildlife to artificial light at night might vary across species, seasons and lamp types. A study conducted by a team led by the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) sheds new light on how exactly ultraviolet (UV) emitting and non-UV emitting street lamps influence the activity of bats in the Berlin metropolitan area and whether tree cover might mitigate any effect of light pollution. The study is published in the scientific journal Frontiers in Ecology and Evolution.

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The secret to bats' immunity

Date:  February 26, 2019

Source:  Duke-NUS Medical School

An international research team led by Duke-NUS Medical School, Singapore, has identified molecular and genetic mechanisms that allow bats to stay healthy while hosting viruses that kill other animals, according to a new study published in the journal Nature Microbiology.

Bats live very long and host numerous viruses, such as Ebola virus, Nipah virus, and severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS) coronaviruses, that are extremely harmful when they infect humans and other animals. Researchers at Duke-NUS Medical School and colleagues wanted to find out how bats can harbour so many of these pathogens without suffering from diseases.

The key, they found, is in the bat's ability to limit inflammation. Bats do not react to infection with the typical inflammatory response that often leads to pathological damage. In humans, while the inflammatory response helps fight infection when properly controlled, it has also been shown to contribute to the damage caused by infectious diseases, as well as to aging and age-related diseases when it goes into overdrive.

The researchers found that the inflammation sensor that normally triggers the body's response to fight off stress and infection, a protein called NLRP3, barely reacts in bats compared to humans and mice, even in the presence of high viral loads.

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Unpredictable food sources drive some bats to cooperatively search for food

Date:  December 13, 2018

Source:  University of Maryland

Humans aren't the only species that have dinner parties. Scientists have observed many animals, including bats, eating in groups. However, little was known about whether bats actively help each other find food, a process known as social foraging.

With the help of novel miniature sensors, an international group of biologists that included University of Maryland Biology Professor Gerald Wilkinson found that bat species foraged socially if their food sources were in unpredictable locations, such as insect swarms or fish schools. In contrast, bats with food sources at fixed locations foraged on their own and did not communicate with one another while foraging or eating. The results of the study were published in the November 19, 2018 issue of the journal Current Biology.

"We were able to show that bats who can't predict where their food will be are the ones that cooperate with each other to forage," Wilkinson said. "And I don't think they are unique -- I think that if more studies are done, we will find that other bat species do similar things."

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Bats vs. Dolphins: Ultimate battle of sonar systems

Date:  November 6, 2018

Source:  Acoustical Society of America

Active sensors are incorporated into a number of technologies, such as meteorology devices and self-driving cars, and use the echo from sound, radio or light waves to locate objects. But despite nearly a century of development, these active sensing technologies still fail to replicate the performance of sonars (sound waves) used in the biological world by dolphins and bats for echolocation.

To find ways to improve human-made active sensing, scientists worldwide study the sonar systems of bats and dolphins. During the Acoustical Society of America's 176th Meeting, held in conjunction with the Canadian Acoustical Association's 2018 Acoustics Week, Nov. 5-9, at the Victoria Conference Centre in Victoria, Canada, Laura Kloepper, assistant professor at Saint Mary's College in Notre Dame, Indiana, will compare bat and dolphin sonar systems, describing her work on how the two animals cope with acoustic interference. She'll use her findings to argue why bats have the superior system.

"I'm on Team Bat," said Kloepper. "But I'm going to be presenting dolphin work to argue why bats are better." She hopes her talk sparks a healthy debate between researchers of both animals.

Kloepper's talk is part of a special session devoted to bat and dolphin sonar systems. Several of the speakers in the session will appear in a press conference devoted to the subject.

Overcoming Interference, Bat and Dolphin Style

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Moths survive bat predation through acoustic camouflage fur

Date:  November 6, 2018

Source:  Acoustical Society of America

Moths are a mainstay food source for bats, which use echolocation (biological sonar) to hunt their prey. Scientists such as Thomas Neil, from the University of Bristol in the U.K., are studying how moths have evolved passive defenses over millions of years to resist their primary predators.

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Misunderstood flying fox could prove bat species demise, warn scientists

Why a further cull of endangered flying foxes' flies against the facts

Date:  November 12, 2018

Source:  University of Bristol

A large fruit-eating bat native to Mauritius is the subject of controversy over the announcement of a major cull to protect the Indian island's fruit crops, despite a lack of evidence as to the extent of damage directly attributed to the endangered species. An international team of researchers, including the University of Bristol, that monitored the damage directly caused by the Mauritian flying fox to commercial fruit has found the bat is responsible for only some, and could be managed effectively without the need to cull. The study is published in the journal Oryx.

As a species of bat largely restricted to Mauritius, the Mauritian flying fox has an important role in helping to pollinate forest canopies and disperse the seeds of large trees in the island's declining forests. However, the bats also feed on cultivated fruit such as mango and lychee and are perceived to cause large economic losses to commercial fruit farmers (annual estimates equate to five million US dollars). Until now, information on the scale of damage directly linked to the bats and the efficacy of mitigation interventions has been lacking.

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Unique study shows how bats maneuver

Date:  November 8, 2018

Source:  Lund University

For the first time, researchers have succeeded in directly measuring the aerodynamics of flying animals as they manoeuvre in the air. Previously, the upstroke of the wings was considered relatively insignificant compared to the powerful downstroke but, in a new study, biologists at Lund University in Sweden have observed that it is on the upstroke of the wings that bats often turn.

"Until now, we have not known very much about what animals actually do when they fly, since we have focused on steady flight. Steady flight is in fact not very common for animals flying out in the wild. We have now conducted direct aerodynamic measurements on bats and we can see how flexible they are. They turn in several different ways depending on where they are in the wing-beat," explains Per Henningsson, a biologist at Lund University.

"It is really fascinating to see how complex and elegant the pattern of movement is, and how the bats choose the best solution just as they decide to start a manoeuvre," he continues.

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Just how blind are bats? Color vision gene study examines key sensory tradeoffs

Date: October 16, 2018

Source: Molecular Biology and Evolution (Oxford University Press)

Could bats' cave-dwelling nocturnal habits over eons enhanced their echolocation acoustic abilities, but also spurred their loss of vision?

A new study led by Bruno Simões, Emma Teeling and colleagues has examined this question in the evolution of color vision genes across a large and diverse group of bat species.

They show that the popular expression of being "blind as a bat" really doesn't hold true. Some bats that have the most advanced type of echolocation appear to have traded UV vision for exquisite hearing, and all bats that do not echolocate but live in caves have also lost UV vision. This suggests that not all bats are blind but some certainly have selected other senses over vision.

"Bats' sensory abilities have long been a source of fascination for evolutionary biologists," said Emma Teeling, the corresponding author of the study, which appears in the advanced online edition of the journal Molecular Biology and Evolution. "Using phylogenetics and molecular biology we are now able to delve more deeply into the evolutionary price of acquiring echolocation and nocturnality."

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Plague marching west: researchers study bats to stop their demise

Scientists work to stay ahead of white nose syndrome, a deadly fungus that has killed millions of bats in the US and Canada

Kathleen McLaughlin in Monarch, Montana

Thu 18 Oct 2018 09.00 BSTLast modified on Thu 18 Oct 2018 16.59 BST

Nate Fuller was just starting out as a bat scientist nine years ago when he entered a massive cave in rural Pennsylvania to look for live animals. Instead, he found himself wading through a distressing muck, the decomposing bodies of thousands upon thousands of dead bats.

That was in the early years of white nose syndrome, the creeping, lethal fungus that has decimated North America’s bat population, killing millions of bats and sparking frantic research and conservation efforts across the United States and Canada.

In Fuller’s case, that traumatic discovery changed the trajectory of his career and led him here this month, to a remote cave site in central Montana, where he is part of a team of bat researchers led by the Wildlife Conservation Society studying the hibernation of western bat populations.

“It was one of the worst things I’ve ever seen,” Fuller remembered of his Pennsylvania experience.

Today, research related to white nose syndrome, one of the most devastating wildlife diseases of modern times, could be the only way to ensure that bats continue to survive.

Across the western United States and Canada, these scientists are nearing the end of one of the most comprehensive studies ever of the hibernation habits of bats. In three years, they have captured and studied 1,500 bats across seven US states and two Canadian provinces and several species. Most bat studies focus on small, specific populations in fixed areas but this one is tracking a whole region, trying to figure out which bats will make it through the coming plague.

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Bat signal: Fireflies' glow tells bats they taste awful

August 22, 2018 by Seth Borenstein

Fireflies flash not just for sex, but survival, a new study suggests.

Scientists wanted to find out if there's more to the lightning bug's signature blinking glow than finding a mate. Some experts had speculated it was a glaring signal to predators, like bats, that fireflies taste bad.

To test out whether the glow acted like a flashing bad Yelp review, researchers at Boise State University put bats and fireflies in front of high-speed cameras. They published their results in Wednesday's journal Science Advances .

The painstaking experiment required researchers to introduce western bats, which had never seen lightning bugs before, to the insects. Later, they hand-painted firefly bellies black, essentially turning off their night lights, avoiding the holes the critters breathe through.

When the bats first saw the unfamiliar lit-up fireflies, they swooped in and munched on them, only to get a bad taste in their mouths.

"They shake their heads, salivate and spit and generally despise their caretakers for giving such a rude meal," said study author Jesse Barber, a Boise State biology professor.

After a few tries, the bats then avoided the glowing fireflies. (Despite the popular misconception, bats aren't blind, a study author noted.)

Once the fireflies essentially taught bats that they taste bad, Barber and colleagues introduced the darkened fireflies. About 40 percent of the painted ones were munched, while none of the normal fireflies were eaten.

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Could we predict the next Ebola outbreak by tracking the migratory patterns of bats?

Lehigh University researchers' framework tracks the ecological drivers of bat migration patterns to predict the next Ebola outbreak

Date: May 22, 2018

Source: Lehigh University

Javier Buceta, associate professor of bioengineering, Paolo Bocchini, associate professor of civil and environmental engineering, and postdoctoral student Graziano Fiorillo of Lehigh University have created a modeling framework that takes a zoonotic perspective on Ebola.

The team's approach works by tracking the migratory patterns of bats, which are believed to be a main carrier of the Ebola virus. Bats, in this instance, are the reservoirs of Ebola. This means that they are carriers and transmitters of the virus, though it does not cause them harm.

"In our model, the appearance of outbreaks is tightly linked to fluctuations in environmental conditions which have an impact on both bat migration patterns and infection rates," says Buceta.

Buceta, Bocchini and Fiorillo worked with satellite information and parameter sampling techniques to create their framework, which integrates data and modeling to predict the conditions linking bats' behavior with the outbreak of Ebola. They have detailed their work in a paper titled "A Predictive Spatial Distribution Framework for Filovirus-Infected Bats" published online today in Scientific Reports.

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Extreme weather 'potentially catastrophic' for bats

By Helen BriggsBBC News

4 May 2018

Extreme weather appears to be disrupting the life cycle of Europe's bats.

Scientists were alarmed to find that some bats in Portugal skipped winter hibernation altogether this year while others gave birth early.

The findings add to growing fears that rising temperatures are having unpredictable effects on bats, birds and other wildlife.

Bats born early in the year may suffer due to lack of insect food.

"It's a phenological mismatch," said Dr Hugo Rebelo of the University of Porto, who is studying the impact of climate change on several Mediterranean bat species.

"What this means is that the bat birth is more or less synchronised with the time of emergence of insects so that when bats give birth there are plenty of resources to feed on and then to feed their own pups.

"With these chaotic weather patterns we are having now in winter and spring we don't know if everything is being mixed up. "

Underground roosts

Rare bat species have been routinely monitored in Portugal at their underground roosts since the 1980s.

In order to survive the winter months, bats must hibernate as there are not enough insects flying around in the winter to meet their energy demands.

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