Bats in the Netherlands, video

This 31 October 2019 video is about bats in South Holland province in the Netherlands.

Freed bats keep friends from captivity days

Thus 2012 video says about itself:

When it comes to feeding, this thumb-sized bat definitely sides with Dracula. Vampire bats are the only mammals on an all-blood diet — and an unsuspecting cow is the perfect prey.

From ScienceDaily:

After release into wild, vampire bats keep ‘friends’ made in captivity

October 31, 2019

Vampire bats that share food and groom each other in captivity are more likely to stick together when they’re released back into the wild, find researchers in a study reported on October 31 in the journal Current Biology. While most previous evidence of “friendship” in animals comes from research in primates, these findings suggest that vampire bats can also form cooperative, friendship-like social relationships.

“The social relationships in vampire bats that we have been observing in captivity are pretty robust to changes in the social and physical environment — even when our captive groups consist of a fairly random sample of bats from a wild colony,” said Simon Ripperger of the Museum für Naturkunde, Leibniz-Institute for Evolution and Biodiversity Science in Berlin. “When we released these bats back into their wild colony, they chose to associate with the same individuals that were their cooperation partners during their time in captivity.”

He and study co-lead author Gerald Carter of The Ohio State University say their findings show that repeated social interactions they’ve observed in the lab aren’t just an artifact of captivity. Not all relationships survived the transition from the lab back into the wild. But, similar to human experience, cooperative relationships or friendships among vampire bats appear to result from a combination of social preferences together with external environment influences or circumstances.

Carter has been studying vampire bat social relationships in captivity since 2010. For the new study, he wondered whether the same relationships and networks he’d been manipulating in the lab would persist or break down after their release in the wild, where the bats could go anywhere and associate with hundreds of other individuals.

Studying social networks in wild bats at very high resolution hadn’t been possible until now. To do it, Simon Ripperger and his colleagues in electrical engineering and computer sciences developed novel proximity sensors. These tiny sensors, which are lighter than a penny, allowed them to capture social networks of entire social groups of bats and update them every few seconds. By linking what they knew about the bats’ relationships in captivity to what they observed in the wild, they were able to make this leap toward better understanding social bonds in vampire bats.

The researchers found that shared grooming and food sharing among female bats in captivity over 22 months predicted whom they’d interact with in the wild. While not all relationships survived, the findings suggest that the bonds made in captivity weren’t just a byproduct of confinement and limited options. The researcher report that the findings are consistent with the idea that both partner fidelity and partner switching play a role in regulating the bats’ relationships.

“Our finding adds to a growing body of evidence that vampire bats form social bonds that are similar to the friendships we see in some primates,” Carter said. “Studying animal relationships can be a source of inspiration and insight for understanding the stability of human friendships.”

The researchers say they’ll continue to work on individual differences in cooperativeness among vampire bats and exploring how individuals go from being strangers to cooperation partners. Taking advantage of their newfound abilities to measure relationships in the wild, they’re also looking into social foraging and whether bats that cooperate within their day roost also go hunting together at night.

This work was supported by the Deutsche Forschungsgemeinschaft, a Smithsonian Scholarly Studies Awards grant, and a National Geographic Society Research Grant.

See also here.

Bats face many threats — from habitat loss and climate change to emerging diseases, such as white-nose syndrome. But it appears that wildfire is not among those threats, suggests a study from the University of California, Davis, published today in the journal Scientific Reports. It found that bats in the Sierra Nevada appear to be well-adapted to wildfire: here.

Butterfly, plant, moth, bat evolution, new research

This October 2016 video from the USA says about itself:

Find out how butterfly pollination behavior influences plant evolution! Drs. Robin Hopkins & Heather Briggs take us through their research into the effects of pipevine swallowtail behavior on the evolution of flower color in the wildflower Phlox.

From the Florida Museum of Natural History in the USA:

Butterflies and plants evolved in sync, but moth ‘ears’ predated bats

October 21, 2019

Summary: A new study cross-examines classic hypotheses about the coevolution of butterflies with flowering plants and moths with bats, their key predators. The findings show flowering plants did drive much of these insects’ diversity, but in a surprise twist, multiple moth lineages evolved ‘ears’ millions of years before the existence of bats, previously credited with triggering moths’ development of hearing organs.

Butterflies and moths rank among the most diverse groups in the animal kingdom, with nearly 160,000 known species, ranging from the iconic blue morpho to the crop-devouring armyworm.

Scientists have long attributed these insects’ rich variety to their close connections with other organisms. Butterflies, they hypothesized, evolved in tandem with the plants they fed on, and moths developed sophisticated defense mechanisms in response to bats, their main predators.

Now, a new study examines these classic hypotheses by shining a light on the early history of Lepidoptera, the order that includes moths and butterflies. Using the largest-ever data set assembled for the group, an international team of researchers created an evolutionary family tree for Lepidoptera and used fossils to estimate when moths and butterflies evolved key traits.

Their findings show that flowering plants did drive much of these insects’ diversity. In a surprise twist, however, multiple moth lineages evolved “ears” millions of years before the existence of bats, previously credited with triggering moths’ development of hearing organs.

“Having a fossil-dated family tree gives us our most detailed look yet at the evolutionary history of moths and butterflies,” said the study’s lead author Akito Kawahara, University of Florida associate professor and curator at the Florida Museum of Natural History’s McGuire Center for Lepidoptera and Biodiversity. “We’ve thought for a long time that flowering plants must have contributed to the extraordinary number of moth and butterfly species we see today, but we haven’t been able to test that. This study helps us see if prior hypotheses line up, and what we find is that the plant hypothesis does, but the bat hypothesis does not.”

The research also suggests lepidopterans are much older than previously thought, with the shared ancestor of today’s butterflies and moths likely appearing about 300 million years ago — roughly 100 years earlier than previous estimates.

A seminal 1964 paper by Paul Ehrlich and Peter Raven used the tightly interwoven relationships between butterflies and flowering plants as the foundation for the theory of coevolution — the idea that different organism groups evolve in response to one another.

As plants developed toxins to ward off hungry caterpillars, they reasoned, butterflies evolved ways of tolerating them. Plants, in turn, would ramp up their weaponry, and the cycle of one-upmanship continued.

Similarly, scientists, including Kawahara, have cited bats as the driving force behind moths’ evolution of special defenses, including ultrasonic-sensitive hearing organs, sonar jamming and long, twisted tails that can deflect an attacker in flight.

Cross-examining these hypotheses requires a trip back in deep time — no easy task with a group of insects that is notoriously rare in the fossil record. Further complicating matters, fossils are often tricky to identify accurately as a moth or butterfly, Kawahara said. One originally labeled as Lepidoptera was later revealed to be a leaf.

Kawahara’s team used two analytical approaches to avoid making the same mistake. They examined previous studies of Lepidoptera fossils, tossing out any examples that seemed questionable. They vetted the 16 remaining fossils with other lepidopterists, looking for consensus that they really represented moths and butterflies. They then used these fossils to date their evolutionary tree, built from more than 2,000 genes from 186 existing moth and butterfly species. To double-check those dates, they carried out the same analysis using just three fossils, each displaying all the hallmark characteristics of a particular Lepidoptera group.

Journeying into moth ‘ears’

A major shocker was the fossil-dated tree’s revelation that nocturnal moths evolved hearing organs nine separate times, four of which occurred around 91 million years ago — about 30 million years before bats dominated the night sky.

What could moths have been listening to in a pre-bat world?

Small pterosaurs, Cretaceous birds, maybe?

“We don’t know,” Kawahara said. He and study co-author Jesse Barber, a bat expert and associate professor at Boise State University, hypothesize that “they probably used these hearing organs to detect the sounds made by other predators, like footfall, flight or rustling, and later co-opted them to pick up on bat sonar.”

Many moths and a few butterflies have “ears” on various parts of the body, depending on the family. The majority of hearing organs, however, are near the wings, the optimal location for swiftly cueing an insect to move toward or away from a sound, said study co-author Jayne Yack, a professor of neuroethology at Carleton University in Ottawa, Ontario.

“It makes sense to have your ears close to flight machinery, if your response to sound is to escape by flight,” she said.

While the finding that some of these organs predated bats came as a surprise, Yack cautioned against jumping to the conclusion that there is no connection between bats and moths’ ability to hear. She pointed out that many species with ears appear just prior to the proposed time when bats developed echolocation, “so something around that time period appears to have been an important selection pressure.”

“The vast majority of ears in today’s Lepidoptera are sensitive to ultrasound, and at least some of them have been shown to function in evading bats,” she said. “Some also evolved after bats first used echolocation. But the evidence does require that we reconsider the currently held assumption that all ears in nocturnal Lepidoptera evolved in response to bat echolocation.”

Nectar straw was a game-changer

The earliest moths likely tunneled and fed inside non-vascular plants such as bryophytes as larvae and had chewing mouthparts as adults. The development of the proboscis, a coiled straw-like mouthpart that can suck up nectar, plant sap and other fluids, helped moth diversity rocket off, Kawahara said. More than 99% of today’s moths and butterflies have a proboscis.

The fossil-dated tree puts the origin of the proboscis around 241 million years ago, coinciding with the time when flowering plants were quickly diversifying. The proboscis helped early moths access nectar and may have enabled them to fly farther and colonize new host plants.

Butterflies, a much younger and less diverse group than moths, did not originate until about 100 million years ago and are just day-flying moths, Kawahara said.

“This study underscores previous studies that show butterflies really belong in the much bigger group of moths,” he said. “We tend to appreciate butterflies because they’re often flashy and charismatic, but we shouldn’t forget about moths, which can be just as striking. Moths and plants were interacting some 50 million years before the first dinosaur roamed the Earth, and those interactions helped lead to the diversity we see on our planet today.”

The origin of bats

This 11 September 2019 video says about itself:

Bats pretty much appear in the fossil record as recognizable, full-on, flying bats. And they show up on all of the continents, except Antarctica, around the same time. So where did bats come from? And which of the many weird features that bats have, showed up first?

New horseshoe bats species discoveries

This 16 March 2019 video from Australia says about itself:

Rescuing a horseshoe bat: this is Lentil

Lentil is an adult female Eastern Horseshoe Bat who was found hanging over a doorway for 24 hours. When she didn’t fly off, the MOP (member of public) called for rescue.

She has some damage to her wing membrane, which in a flying fox would probably be a death sentence, but microbats seem to be able to regenerate quite a lot of wing membrane after damage and fly again.

I don’t know what has caused the membrane damage; Lentil didn’t come with a case history and she hasn’t mentioned anything to us about her recent history.

She’s in care now with the Princess, who is great with micros and was delighted to care for an uncommon (to our city) little horseshoe bat.

You can see from the shape of her nose why she’s called a horseshoe bat. In 12 years I’ve never rescued a horseshoe bat in my territory. I don’t know if she’s come in on a truck from out in the country or how she got there. The MOPs haven’t been out of town in the last few weeks.

It’s possible that there are horseshoe bats in the area – Sydney is certainly within the geographical distribution area for horseshoe bats, it’s just that I haven’t heard about any being rescued in the city before. The house backs onto a golf course which is nicely treed.

Her name? I actually called her Lentil as Anything. She was quite cranky, and there is a rock band called Mental as Anything… and Lentil came from Lenthall Street.

The Princess says that’s an appalling name for a beautiful little batty, so she will, no doubt, rename her.

Generally horseshoe bats are cave dwellers but they will roost in tree hollows. They have short broad wings and low wing loading, which means they have slow highly manoeuvrable flight. They can hover, and move successfully in dense branches and shrubs. They can hang and catch their insect prey, or they can pursue their prey aerially. Their dominant food is moths but they’ll eat beetles, flies, crickets, bugs, cockroaches and wasps. (ref: Sue Churchill, Australian Bats, 2nd edition).

From the Field Museum in the USA:

There are way more species of horseshoe bats than scientists thought

August 22, 2019

Horseshoe bats are bizarre-looking animals with giant ears and elaborate flaps of skin on their noses that they use like satellite dishes. There are about a hundred different species of horseshoe bats — and that number is only going to grow. By studying the DNA of horseshoe bat specimens in museum collections, scientists have discovered that there are probably a dozen new species of horseshoe bat that haven’t been officially described yet.

If you’ve never seen a horseshoe bat, you’re missing out. Their comically large ears are only rivaled for wackiest feature by their nose leaves, little flaps of skin that spread outward from their faces like petals. If you grew up with siblings who would say, “That’s you”, when they saw an ugly creature on TV, they’d have a field day with horseshoe bats.

But while they have faces only a biologist could love, horseshoe bats have caught the interest of scientists studying the bat family tree. There are more than 100 recognized species of horseshoe bats, and researchers now believe that number could be still higher. In a study published in BMC Evolutionary Biology, researchers from the Field Museum, National Museums of Kenya, and Maasai Mara University used gene sequencing to identify up to 12 new species of horseshoe bats. They also cast doubt on the validity of several recognized species.

MacArthur Curator of Mammals and senior author of the study Bruce Patterson says, to put it simply, “We found a lot more species than we thought were there.”

“Horseshoe bats are defined by the broad flap of skin on their upper lip. It serves as a radar dish for their echolocation calls,” says Patterson. “I think they’re totally bizarre and for students of biology that bizarreness is what makes them so fascinating.”

Terry Demos, post-doctoral researcher and lead author of the paper, also agrees that horseshoe bats are unique looking — “You could say there’s beauty in the elaborateness of the nose, I mean it is so intricate.”

The researchers wanted to study the bats because, despite being so rich in different species, little is known about their evolutionary history. East Africa has remained understudied, even though it’s one of the most diverse regions in the world. For centuries, colonialism meant that European researchers were the only people with access to the land. Patterson and Demos hope that studies like this one will help equip local scientists with the tools they need to research their own land. “We’re trying to understand evolutionary history in an understudied area,” says Demos, “while also building in-country resources.”

The research team examined hundreds of bat specimens from the collections at the Field Museum and National Museums of Kenya. Using small samples of tissue, they sequenced the bats’ DNA to see how closely related they were to each other, like 23AndMe testing on a species level.

The genetic similarities and differences between the bats suggested that some distinctive groupings could be new species. Some of these new species may be what scientists call “cryptic” — visually, they look very similar to species we already know about, but genetically, they’re different enough to be considered their own separate species. These cryptic species were hiding in plain sight in the museums’ collections, waiting to be discovered.

While the study did suggest that there are more species of horseshoe bat than previously imagined, new species will not be officially named until the team carries out the next part of their research. To designate a new species, researchers will need to examine the bats’ teeth and skulls to see how their physical traits differ. They’ll also need to compare the bats’ echolocation calls, since different bat species that live near each other often make their calls at different frequencies, like different channels on a walkie-talkie.

The researchers are excited by the possibilities that come with rewriting the horseshoe bat family tree. “The implications of this study are really countless,” says Patterson. “Bats eat insects that carry diseases, what are the implications of that? We can also use this to designate areas for conservation.”

A new study finds that the muscles in bats’ wings operate at a significantly lower temperature than their bodies, especially during flight: here.

African bats studied with satellite tags

This 2016 video says about itself:

Yellow Winged Bat (Lavia frons)

The beautiful Yellow Winged Bat. Common across East and West Africa in woodlands.

From the University of Helsinki in Finland:

Tiny GPS backpacks uncover the secret life of desert bats

August 16, 2019

A new study from the University of Helsinki using miniaturized satellite-based tags revealed that during drier periods desert bats must fly further and longer to fulfil their nightly needs. According to researchers this signals their struggle in facing dry periods.

Wildlife tracking has revolutionized the study of animal movement and their behavior. Yet, tracking small, flying animals such as desert bats remained challenging. Now a new generation of miniaturized satellite-based tags is allowing unique insights into the life of these mysterious mammals.

Researchers used 1 g GPS devices to reconstruct the movements of yellow-winged bats, one of two false vampire bats occurring in Africa and one of the few desert bats large enough to carrying this innovative technology. “GPS tags have seen up to now a limited use with insectivorous bats due to weight constraints and low success in data collection — we achieved great results in tracking such a light species,” says Irene Conenna, a PhD candidate at the University of Helsinki and the lead author of the study.

Future under the changing climate?

“Bats are some of the most successful desert mammals. Powered flight allows them to efficiently track scarce resources and their nocturnal lifestyle buffers them from the baking sun. However, they still struggle to find enough resources during the drier periods of the year,” says Ricardo Rocha, one of the co-authors of the paper.

The study was conducted in Sibiloi National Park, Northern Kenya, along the shores of Lake Turkana, the world’s largest desert lake. Researchers placed GPS loggers in 29 bats, 15 in the rainy season and 14 in the dry and, for one week. Their whereabouts were recorded every 30 to 60 minutes every night. This revealed that during dry periods bats used larger home ranges and had extended activity periods, potentially to compensate for a shortage in food resources.

Bats comprise roughly one fifth of all mammal species and deserts are home to over 150 bat species. They display wide variation in morphology, foraging behavior, and habitat use, making them an excellent indicator group for assessing how species respond to changes in their habitats. “The responses exhibited by bats offer important insights into the responses of other taxonomic groups,” explains Conenna. “These new miniaturized satellite-based tags now allow us to better understand how increased aridity affects bats foraging efficiency, leading us one step forward to understanding limits in aridity tolerance and impacts of climate change,” adds Conenna.

Deserts around the world are getting warmer and as they warm desert creatures need to cope with even harsher conditions. “Understanding how animals cope with seasonal changes is key to understand how they might react to the challenges in the horizon. New technological devices, such as miniaturized satellite-based loggers, go a long way to help us in this task”, adds Mar Cabeza, senior author of the study, University of Helsinki.

Bat faeces and biodiversity in Indonesia

This 2015 video says about itself:

Bat Man of Borneo | Expedition Raw

Braving guano, urine, and infectious diseases is all in a day’s work for bat ecologist Donald McFarlane, who descends into the depths of Borneo’s Gomantong Caves [in Malaysia] to study the bats that live there.

From James Cook University in Australia:

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?

April 25, 2019

Summary: Examining a 3-meter stack of bat feces has shed light on the landscape of the ancient continent of Sundaland. The research could help explain the biodiversity of present-day Borneo, Sumatra, and Java. It could also add to our understanding of how people moved through the region.

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.

“Eating insects that have been feeding on tropical grasses results in faeces with a characteristic chemical imprint. It’s quite different from the result you’d get from eating insects that fed on tropical trees.”

According to the bat record the landscape around Saleh Cave (now featuring lush rainforest) was once dominated by tropical grasses.

“Combined with other cave studies in the region, this leads us to support the corridor theory, and also gives us some confidence as to the extent of the corridor,” Dr Wurster said.

The corridor could also shed light on human pre-history.

“A savanna corridor, which would be much more easily traversed than rainforest, might help to explain how people moved relatively quickly through this region and on to Australia and New Guinea.”

‘Savanna in equatorial Borneo during the late Pleistocene’ is published in the latest edition of Scientific Reports.

Dr Chris Wurster is a Senior Research Associate at James Cook University, specialising in stable isotope geochemistry.

Migratory bats’ sunset orientation

This 2014 video from the USA says about itself:

Spring Migration of the Indiana Bat

Short documentary following biologists as they track migrating Indiana bats.

From the Forschungsverbund Berlin in Germany:

Compass orientation of a migratory bat species depends on sunset direction

April 4, 2019

Scientists combined a mirror experiment simulating a different direction of the setting sun and a new test procedure to measure orientation behavior in bats to understand the role of the sun’s position in the animals’ navigation system. The results demonstrate for the first time that a migratory mammal species uses the sunset direction to calibrate their compass system.

Whether it is bats, wildebeest or whales, millions of mammals move over thousands of kilometres each year. How they navigate during migration remains remarkably understudied compared to birds or sea turtles, however. A team of scientists led by the Leibniz-IZW in Berlin now combined a mirror experiment simulating a different direction of the setting sun and a new test procedure to measure orientation behaviour in bats to understand the role of the sun’s position in the animals’ navigation system. The results demonstrate for the first time that a migratory mammal species uses the sunset direction to calibrate their compass system. Furthermore the experiment, which is published in Current Biology, indicates that this capacity is not inherited and first-time migrating young bats need to learn the importance of the solar disc at dusk for nightly orientation.

The experiment that scientists Oliver Lindecke and Christian Voigt from the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) designed and conducted together with colleagues from Latvia and the United Kingdom was based on two steps: First, several Soprano pipistrelle bats (Pipistrellus pygmaeus) were randomly assigned into two groups. At nightfall during their migration period, one group could watch the natural sunset at the Latvian Baltic Sea shore. The other group however watched the sun going down via a large mirror which was reversing the direction of the natural sunset exactly 180°. For the latter animals, the real sunset was blocked from vision by the taped sidewall of their holding cages. Later at night, animals of both groups were transported inland, away from the beach of the Baltic Sea, for the second step of the experiment: On a forest meadow, one bat after the other got released remotely from a specially designed circular release box. By the help of this box, the very direction an animal took when it left it, could be recorded. Prior studies showed that take-off orientations could be used as a proxy for departure flight orientation in these bats.

“The new orientation assay, the circular release box for bats, ruled out any visual influence at takeoff and allowed us to compare the directions bats of both groups where taking,” explains Lindecke. “The results show two fundamental aspects in bat navigation: Firstly, the setting sun’s direction plays a crucial role because there is a significant difference in the bats’ orientation with the group which experienced the mirrored sunset departing in opposite direction compared to the control group. And secondly, only adult bats showed directional preferences,” Lindecke summarizes the results. “Subadults displayed random orientation in both groups, which suggests to us that young bats need to learn long-distance navigation during migration from older conspecifics,” concludes Christian Voigt, senior author and head of the Department of Evolutionary Ecology at the Leibniz-IZW. How this learning process works and which social factors and practices contribute to it remains unknown and needs further investigation.

Mammals remain remarkably understudied with regard to navigation during migration. One of the reasons I a lack of experimental assays that measure a correlate of migratory orientation such as those that exist in birds and sea turtles. The larger migratory mammals, for example wildebeest or whales, are challenging to handle for any experimental work. Bats could fill this void as they have emerged as an important study model in movement ecology. They combine high ecophysiological diversity with a variety of movement behaviours. Bat eyes evolved to sense a wide range of light and a broad spectrum of wavelengths. Presumably, insectivorous bats rely heavily on vision like fruitbats when orienting over long distances since echolocation and path integration are ineffective and error-prone at distances larger than a few dozen meters. The results of this study are the first empirical evidence for the specific cues and mechanisms a migratory mammal uses for navigation.

Scientists have discovered that two major forces have shaped bat skulls over their evolutionary history: echolocation and diet. Their findings help explain the wide diversity of skull shapes among bats and reveal the intricate details of how evolutionary pressures can shape animal bodies: here.

On moonless nights in a tropical forest, bats slice through the inky darkness, snatching up insects resting silently on leaves — a seemingly impossible feat. New experiments at the Smithsonian Tropical Research Institute (STRI) show that by changing their approach angle, the echolocating leaf-nosed bats can use this sixth sense to find acoustically camouflaged prey. These new findings, published in Current Biology, have exciting implications for the evolution of predator-prey interactions: here.

Berlin bats and light pollution

This 26 July 2018 video from Germany says about itself:

Bats in bedroom @4 am in the middle of Berlin!!!

My friend left the window in his bedroom open and some bats decided to visit!

From Forschungsverbund Berlin in Germany:

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

A complex relationship

March 27, 2019

Summary: A study 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.

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.

Natural sunlight sets the pace of day and night on our planet. Over millions of years, wildlife and people have adapted to the rhythm of the natural photoperiod. As creatures of daytime, humans have expanded their ecological niche into night-time by inventing and using artificial light. Yet nocturnal animals such as bats may suffer from the detrimental effects of artificial light generated by street lamps, a phenomenon now recognised as light pollution. As it turns out, bat responses to light pollution were complex. “We observed a higher activity of two pipistrelle bat species, the common pipistrelle and Nathusius’ pipistrelle, in areas with high numbers of UV emitting street lamps”, explains Tanja Straka, scientist at the IZW’s Department of Evolutionary Ecology and first author of the study. These opportunistic species may feed on insects that are attracted to UV emitting lamps. “However, all other species were less active at and even repelled by the lamps, irrespective of whether the light they emitted did or did not contain UV light”. adds Straka.

The novelty of this study is that these effects were considered in relation to tree cover. Not only do trees provide bats with shelter during daytime, trees may also provide shade for bats in illuminated areas. “Our goal was to determine whether and how tree cover influences any responses of bats to artificial light”, says Straka.

The team found that the response of bats to artificial light was intensified in areas with high tree cover. For example, the attraction of Pipistrellus pipistrellus to UV light was more pronounced when many trees were present, probably because UV light attracted insects from the vegetation. On the other hand mouse-eared bats (Myotis spp.) were less frequently recorded in areas with a high number of street lamps (irrespective of UV or no UV emission) and lots of trees. Mouse-eared bats seem to be particularly light-sensitive and avoid illuminated areas even when these include trees or shrubs. The team also found that high-flying insectivorous bats were more active in areas when the light emission from LED street lanterns was dampened by a high tree coverage than in areas with many LED lanterns and no trees.” LED lights do not attract large numbers of insects and therefore they are not attractive as foraging grounds for high-flying bats; they might even be repelled by light spillover from LED lamps. Tree cover seems to reduce light spillover, which enables high-flying bats to fly in the shadow of the tree canopy,” Straka explains.

These results are based on the analysis of more than 11,000 bat calls recorded during three months at 22 sites in the Berlin city area. Bat calls were identified by species and the activity of bats was calculated for each species and site. These data were compared with features of the landscape, such as tree cover and the intensity of light pollution as estimated by remote sensing (i.e. satellite-based data). In addition, the exact location of street lamps and information on UV light emission was used to estimate the level of light pollution in the study area.

“The bottom line is that for bats the relation between artificial light and vegetation is complex and it varies between species, yet overall artificial light at night has negative consequences for bats,” concludes Christian Voigt, the Head of Department. “Even those species that may hunt at street lamps opportunistically will suffer on the long run from the constant drain of insects dying at street lamps. Trees are important for urban bats, not only as a shelter but also as a source for prey insects. Hence artificial light should be avoided in habitats with many trees.” Adding trees in highly lit areas or turning off lights when the area is not in use could substantially contribute to the conservation of bats and possibly also other nocturnal wildlife, because trees provide shade and refuge that bats urgently need.

Artificial light influences the behaviour of many nocturnal animals such as bats, which are very sensitive to all types of lighting. Particularly critical is the illumination of natural caves in which bats roost. Cave illumination is widespread in tourist areas worldwide and disturbs the animals in their resting places. Researchers of the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) and the Max Planck Institute for Ornithology (MPIO) have now investigated how the illumination of bat caves affects the animals’ behaviour and whether the colour of light makes a difference on their flight and emergence activity. Although red light irritates the small mammals somewhat less than white light, from the researchers’ point of view neither the entrance nor the interior of bat caves should be illuminated if bats are present. The results are published in the journal Global Ecology and Conservation: here.

Light at night is harmful for amphibians, new research shows. Exposure to light at night has potential to make amphibians more susceptible to additional stressors: here.

A new study demonstrates that the ears of bats come with a ‘built-in ambulance’ that creates the same physical effect as the sound of an ambulance passing by. Researchers 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: here.

Light pollution may be increasing West Nile virus spillover from wild birds: here.

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.

A scientist used chalk in a box to show that bats use sunsets to migrate. Oliver Lindecke devised a new device that was partly inspired by a snow-covered Berlin street: here.