How Nathusius’ bats migrate


This 2013 video from England says about itself:

Nathusius Bat Project in London

Nathusius bats have been regularly found in bat boxes at this site in London for the last ten years. A scientific study started in 2012 with the help and support of the Bucks Bat Group. Ringing and mist-netting are now being regularly carried out under licence from Natural England.

From Forschungsverbund Berlin in Germany:

Bat-mobile with cruise control

Bats migrate at the most energy-efficient flying speed for maximum range

February 27, 2019

Summary: A new study investigated the energy requirements and travel speeds of migrating Nathusius’ bats (Pipistrellus nathusii).

Aerial migration is the fastest, yet most energetically demanding way of seasonal movements between habitats. A new study led by scientists at the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) investigated the energy requirements and travel speeds of migrating Nathusius’ bats (Pipistrellus nathusii). Using a wind tunnel experiment to determine the exact energy demands of different flying speeds and a field study to record actual travel speeds of migrating bats, the scientists demonstrated that bats travel at the speed where their range reaches a maximum, enabling them to cover long distances with a minimum amount of energy. How the researchers tracked down this cruise control is published in the Journal of Experimental Biology.

For many taxa, and bats in particular, scientists still lack a clear understanding of the energy requirements for migration. A team of scientists lead by Sara Troxell and Christian Voigt from the Leibniz-IZW designed an ambitious experimental study to make substantial progress on this question. The first part of the study was a wind tunnel experiment combined with measurements in a respirometry chamber. The chamber allowed the scientists to precisely track the CO2 enrichment in the air from the breath of the bats, from which they calculated the metabolic rate during flight. By repeating these measurements directly before and after one-minute flights at various speeds in the wind tunnel, the scientists recorded flight metabolic rate in relation to air speed and then calculated the flight speed with the best energy to distance ratio. The second part of the study was conducted at a migratory corridor along the Baltic Sea coast in Latvia. Using the echolocation calls of migrating Nathusius’ bats, the scientists established the flight trajectories of these bats which allowed them to measure the actual speed of migration. “Our study confirms that the observed flight speeds are consistent with the expectation that migratory bats practice optimal flight speeds for covering the largest distance with the least amount of energy,” Troxell and Voigt concluded. This speed is around 7.5 meters per second, equivalent to 27 kilometres (16 miles) per hour.

The field study also facilitated the comparison of the flight speed of migrating bats with the speed of bats foraging for insects. Foraging bats fly at significantly lower speeds than the most efficient speed determined in the wind tunnel experiments. “When foraging in a dune forest, bats performed sharp turns in order to catch insects,” Troxell explains. “These tight turns require slower flight speeds and the overall speed might be reduced in anticipation of such turns.” Previous studies in less confined habitats revealed average foraging speeds that were much closer to the calculated ideal speed.

Data of migratory flight speed and flight energy expenditure make it possible to estimate energetic requirements of trans-continental migration in small-sized bats. “However, it is important to realise that our insights into the migratory behaviour of bats are still in their infancy,” Voigt explains. Extrapolation of the energy needed by a Nathusius’ bat travelling a distance of 2,000 kilometres from northeastern Europe to hibernacula sites in western or southern France result in an estimated total energy demand of almost 300 kilojoules. A journey of this length needs at least 12 days to complete when flying in a straight line. Currently, the exact routes, flying hours and distances flown per night are still unknown, so need to be investigated in more detail.

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How bats survive viruses


This 2011 video says about itself:

Meet the World’s Biggest Bat | National Geographic

With their giant wingspans, flying foxes are the world’s biggest bats. Australia’s black flying foxes are a prime example, with wingspans up to six feet (two meters)!

From Duke-NUS Medical School in Singapore:

The secret to bats’ immunity

February 26, 2019

Summary: Bats‘ ability to host deadly viruses without getting sick could help shed light on inflammation and aging in humans.

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.

“Bats’ natural ability to dampen inflammation caused by stress and infection may be a key mechanism underlying their long lifespans and unique viral reservoir status,” said Dr Matae Ahn, first author of the study and an MD-PhD candidate of the Emerging Infectious Diseases (EID) Programme at Duke-NUS Medical School.

The researchers compared the responses of immune cells from bats, mice and humans to three different RNA viruses — influenza A virus, MERS coronavirus, and Melaka virus. The inflammation mediated by NLRP3 was significantly reduced in bats compared to mice and humans.

Digging further, they found that ‘transcriptional priming’, a key step in the process to make NLRP3 proteins, was reduced in bats compared with mice and humans. They also found unique variants of NLRP3 only present in bats that render the proteins less active in bats than in other species. These variations were observed in two very distinct species of bats — Pteropus alecto, a large fruit bat known as the Black Flying Fox, and Myotis davadii, a tiny vesper bat from China — indicating that they have been genetically conserved through evolution. Further analysis comparing 10 bat and 17 non-bat mammalian NLRP3 gene sequences confirmed that these adaptations appear to be bat-specific.

What this implies, the researchers explain, is that rather than having a better ability to fight infection, bats have a much higher tolerance for it. The dampening of the inflammatory response actually enables them to survive.

“Bats appear to be capable of limiting excessive or inappropriate virus-induced inflammation, which often leads to severe diseases in other infected animals and people,” said Professor Wang Lin-Fa, Director of Duke-NUS’ EID Programme and senior author of the study. “Our finding may provide lessons for controlling human infectious diseases by shifting the focus from the traditional specific anti-pathogen approach to the broader anti-disease approach successfully adopted by bats.”

Professor Patrick Casey, Duke-NUS Medical School’s Vice Dean for Research, noted of the findings: “With this study, our researchers have advanced our understanding of an area that had long remained a mystery. This is yet another example of the world-class research and global collaboration that is a hallmark of Duke-NUS.”

Deaf moths’ sounds to escape from bats


This 2010 video says about itself:

Development of the Orchard Ermine (Yponomeuta padella) from caterpillar to moth. Filmed at the Wollenberg, Hesse, Germany.

From the University of Bristol in England:

Deaf moth evolves sound-production as a warning to outwit its predator

February 5, 2019

A genus of deaf moth has evolved to develop an extraordinary sound-producing structure in its wings to evade its primary predator the bat. The finding, made by researchers from the University of Bristol and Natural History Museum, is described in Scientific Reports today [Tuesday 5 February].

It’s already known that some species of moth have evolved a range of defensive mechanisms to evade insectivorous bats’ highly-tuned echolocation (biosonar) detection skills. The discovery of a wingbeat-powered sound producing structure in the wings of a deaf moth is completely new.

Many larger species of moth use ears tuned to detect the echolocation calls of bats to provide an early warning of approaching bats allowing them to perform evasive manoeuvres. While others, such as some silk moths, have hindwing tails that produce salient echoes which act as false targets to bats — like the towed decoys fighter planes use against radar guided missiles.

The team of researchers from Bristol’s School of Biological Sciences and the Natural History Museum, London, were studying a group of smaller British moths known as the small ermine moths (Yponomeuta species), and discovered that despite their lack of hearing they were making continual clicking sounds whenever they fly. Unlike other species of moths, that produce sound in response to detecting an approaching bat, small ermine moths have evolved to produce continual warning sounds.

The sounds these moths produce are very similar to sounds produced by larger moths, such as the tiger moths, which warn bats of the moth’s distastefulness or toxicity (known as acoustic aposematism). At night an unpalatable moth cannot provide a bat with a conspicuous warning colour, so instead it warns its predator acoustically. The team suggest that small ermine moths are acoustically mimicking unpalatable, sound producing moths, to warn bats of their own distastefulness.

Typically, anti-bat sounds are produced by structures called tymbals, small areas of thin cuticle on a moth’s body, which are connected to a muscle. As the muscle contracts, the tymbal buckles and produces a click, then as the muscle relaxes, the tymbal snaps back to its resting state and produces another click. However, the wing-based tymbals of small ermine moths are not connected to a muscle, instead sound production is initiated by the moth’s wingbeat during flight.

Liam O’Reilly, the study’s lead author and a PhD student at Bristol’s School of Biological Sciences, said: “Bat defences in larger moths are well studied, however, the defences in smaller moths are not.

“Many animals use a conspicuous visual signal such as bright colouration to warn their predators of a defence, but at night an unpalatable moth cannot provide a bat with a visual warning signal, so instead it warns its predator acoustically through a clear sound — loud high frequency (ultrasonic) clicks.

“The fact that sound production in these moths has remained undiscovered for so long reminds us of how little we know of the complex acoustic world of bats and moths.”

Following this discovery, the team are working with material scientists to find out the exact mechanism by which the small ermine moth tymbal produces sound. Specialists in buckling mechanics are working on modelling the system to artificially recreate the sounds of these moths.

Bats cooperate for finding food


This 2014 video says about itself:

Secrets and Mysteries of Bats – Nature Documentary

This 48-minute documentary explores the world of bats and the scientists who study them — including the late Donald Griffin, a Harvard zoologist who was the first to describe their echolocation ability in the 1940s. Using 3-D graphics to recreate the bats’ acoustic vision and shooting with infra-red and high-speed cameras, this film offers an exhilarating “bat’s-eye” journey into the night.

From the University of Maryland in the USA:

Unpredictable food sources drive some bats to cooperatively search for food

December 13, 2018

Summary: With the help of novel miniature sensors, biologists have 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.

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.”

The researchers selected five bat species from around the world for the study — two species with unpredictable food sources and three with predictable food sources. They fit each bat with a small, lightweight sensor that operated for up to three nights. Because the sensor only weighed approximately 4 grams, it did not hinder the bat’s movements. The sensor recorded GPS data to log each bat’s flight path and audio in ultrasonic frequencies to document bat calls. The researchers recaptured each bat to download the data. In all, the researchers tracked 94 bats in this study.

Edward Hurme, a UMD biological sciences graduate student in Wilkinson’s laboratory and a co-lead author of the paper, tracked one of the bat species — the Mexican fish-eating bat, which lives on a remote Mexican island.

“We took a fishing boat to an uninhabited island where these bats live and camped there for a month at a time”, Hurme said. “Field work can be challenging. One time, a hurricane came and all we could do was hide in the tent. Fortunately, we survived and so did our data.”

After collecting data on all five bat species, the researchers charted the bats’ flight paths and analyzed the audio recordings. They listened for the distinctive, species-specific calls the bats make during normal flight and when trying to capture prey. The research team used this information to map where and when the bats found and ate food and whether other bats were nearby.

The results showed that the three species of bats that eat predictable food sources, such as fruits, foraged on their own. When they found food, they also ate alone. This makes sense, according to Wilkinson, because they didn’t need any help finding food. In fact, having other bats around could create harmful competition for food.

In contrast, the two species of bats with unpredictable food sources often flew together with other members of their species. Moreover, when a tracked bat found prey, other individuals nearby also began to forage. The findings suggest that these bats forage cooperatively and socially within their own species.

The researchers also found that socially foraging bats may eavesdrop on one another by staying close enough to hear each other’s feeding calls.

“We tested this hypothesis by playing recordings of white noise, normal calls and feeding calls for these bats to hear”, Hurme said. “We found that bats who heard normal calls became more attracted to the speakers than those who heard white noise. And when we played feeding calls, bats dive-dombed the speakers.”

The next step for this research is to investigate what strategies bats use in social foraging. In particular, Hurme hopes to discover whether these bats pay attention to the identity of their fellow foragers.

“We would like to know if socially foraging bats will follow any member of their own species or if they prefer specific individuals who are the most successful at finding food”, Hurme said. “There is some evidence that bats can recognize each other by voice, so we are working on ways to identify individuals by their calls.”

Bats at Panama bird feeders


This video says about itself:

Bats Visit Panama Feeders in Middle of the Night – Nov. 13, 2018

Birds aren’t the only winged creatures you’ll find enjoying the offerings at the Panama fruit feeders. Watch here as a group of bats take turns foraging on sweet nectar in the middle of the night!

Watch LIVE 24/7 with highlights and viewing resources at http://allaboutbirds.org/panamafeeders

The Panama Fruit Feeder Cam is a collaboration between the Cornell Lab of Ornithology and the Canopy Family.