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This Australian moth may be the 1st insect ever discovered to use stars for long-distance navigation
When you buy through links on our articles, Future and its syndication partners may earn a commission. Stand outside one spring night in southeastern Australia and you may be able to witness one of the biggest insect migrations in the world, as billions of brown Bogong moths (Agrotis infusa) flit across the sky. Each year in the spring, the moths migrate around 620 miles (1,000 kilometers) north to the Australian Alps, where they can avoid the heat by hiding in cool caves until the fall, when they return to their breeding grounds. While migration is not uncommon in insects, the Bogong moth's migration has been of particular interest to experts — how does a moth travel to a place it's never visited before? Researchers believe they now have the answer: stellar navigation. This would make the Bogong moth the first insect to use the stars for long-distance navigation as it makes its extended migratory journey. Stellar navigation has a long history for both humans and animals, from ancient Polynesians to migratory birds. Given the stars' dominance in the night sky, it's not surprising for experts to think that other animals, like insects, may also use these twinkling lights for navigating. "We knew from a previous study that the moths can use the geomagnetic field to navigate, but they only seemed to be able to do so in combination with visual landmarks, so we were thinking about what kind of landmarks these could be," explained Andrea Adden, a researcher at the Francis Crick Institute in the United Kingdom. "If you go to the Australian bush, where these moths live, and look around you at night, one of the most obvious visual landmarks is the Milky Way, which is always visible to some extent, independent of time of night and season," Adden said. "We know that daytime migratory insects use the sun, so testing the starry sky seemed an obvious thing to try." To test whether these moths are truly using the stars to navigate, the researchers captured several using a light-trap. This required the team to traverse into the dark, cold caves where the moths were resting during their migration, which, for some of the team, proved to be too challenging. According to Eric Warrant, a researcher at the University of Lund in Sweden and the leader of the project, "One of the most embarrassing [stories] was when Lena Nordlund from Swedish Radio (who was with us in Australia doing a documentary) asked why I always sent [the] youngsters in the cave and I always sat outside. I was forced to admit I was claustrophobic and was scared of going in — something that of course she included in the documentary." Though Warrant was not comfortable going into the caves, that didn't stop his collaborator, David Dreyer, also a researcher at the University of Lund, from challenging Warrant to a little competition to see who could catch the first Bogong moth of the migratory season. This competition lasted over a decade, with 20 different seasonal opportunities to compete. "[I] dominated this competition, [winning] 19 migratory seasons," Dreyer explained jokingly. "[My] 19 wins would remain unreported, until now. Justice at last." After capturing the moths, the team then placed them in a planetarium-like flight simulator, which included multiple projectors that could be programmed to give specific scenery. The simulator also blocked Earth's magnetic field, forcing the moths to try to navigate in the simulation by their eyesight alone. The researchers also attached electronic sensors to the moths to measure their brain activity. As Bogong moth brains are around the size of a grain of rice, adding the sensors was incredibly time-consuming. "Studying the neural basis of how these moths navigate reveals new processing mechanisms in the insect brain," Adden noted. "Even though human brains and insect brains are obviously very different, it often turns out that the computational principles are remarkably similar, so perhaps we can even learn something from moths that, one day, helps reveal something about the human brain." Once the moths were prepared, the researchers waited for evening in the outback, and then began to test the moths by recording their virtual flight paths in the simulator. "We continued this process until we had used all the prepared moths," Dreyer said. "The following morning was dedicated to data analysis. This routine continued until every moth from the previous catch had been tested — after which we would head out to catch a new batch." While studying the Bogong moths, the COVID-19 pandemic hit Australia, forcing a lockdown. For Adden, this meant being stuck out in the field. "A colleague and I were just wrapping up the field season in early 2020 when Australia entered its first Covid-19 lockdown, and the two of us were locked down at the field station for about a month," she said. "This wasn't as bad as it might seem — with no other humans in sight, we spent our days analyzing data, watching local wildlife and learning to sew." Adden even took the time to practice her astrophotography skills, taking photos of the very night sky her research subjects leveraged to navigate. After years of analysis, the researchers found that the Bogong moths fly in the seasonally appropriate direction (north or south) depending on the stars in the night sky, suggesting that they do in fact use the stars to guide them. "The stars are a very consistent cue. Even though the starry sky rotates throughout the night, the brightest part of the Milky Way is always in the South of the Southern celestial hemisphere," said Adden. "That makes it a very stable compass cue that is reliable not just across nights and seasons, but across centuries." From the moth's brain activity, the team also saw responses specific to certain rotations of the night sky in the flight simulator, and determined that their brains were the most active when they were "flying" in the right direction of their migration. While the Bogong moth is not the only insect to use the stars for guidance, it is the first to do so for long-distance journeys, scientists said. 'A previous study established that dung beetles use the stars to guide short-distance movements, but the beetles only travel a short distance (maybe 5-20 meters) as opposed to flying 1,000 km during a migration,' Ken Lohmann, a researcher at the University of North Carolina, Chapel Hill who was not involved in the study, told Studying how animals like moths navigate is not only fascinating, but can also help ensure the moth populations remain at a healthy level. "The Bogong moth population declined dramatically after the recent drought and 2020 bushfires," explained Adden. "Understanding how their migration works, and which cues they use to navigate, may help us protect these insects, which in turn helps the entire alpine ecosystem of which the moths are an integral part — e.g., as food for pygmy possums and all sorts of birds during the summer months." Part of that conservation work is looking at the role urbanization and, more specifically, light pollution plays in affecting the moths' migratory path. "Light pollution may well be a problem for Bogong moths during their migration,' Adden said. 'On their way from Southern Queensland to the Australian Alps, they pass several major cities, such as Canberra, which can be disorienting and trap the moths. In fact, this happened several years ago, when a cloud of moths briefly took over the Australian Parliament." While the Bogong moth shows the ingenuity of animals, for researchers and conservationists alike, understanding the animal navigation process as a whole is key to understanding their lifestyle, and therefore being able to protect them further. "A central lesson of animal navigation is that species almost always have multiple ways to guide themselves," said Lohmann. This study was published online today (June 18) in the journal Nature.
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7 hours ago
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This Australian moth may be the 1st insect ever discovered to use stars for long-distance navigation
When you buy through links on our articles, Future and its syndication partners may earn a commission. Stand outside one spring night in southeastern Australia and you may be able to witness one of the biggest insect migrations in the world, as billions of brown Bogong moths (Agrotis infusa) flit across the sky. Each year in the spring, the moths migrate around 620 miles (1,000 kilometers) north to the Australian Alps, where they can avoid the heat by hiding in cool caves until the fall, when they return to their breeding grounds. While migration is not uncommon in insects, the Bogong moth's migration has been of particular interest to experts — how does a moth travel to a place it's never visited before? Researchers believe they now have the answer: stellar navigation. This would make the Bogong moth the first insect to use the stars for long-distance navigation as it makes its extended migratory journey. Stellar navigation has a long history for both humans and animals, from ancient Polynesians to migratory birds. Given the stars' dominance in the night sky, it's not surprising for experts to think that other animals, like insects, may also use these twinkling lights for navigating. "We knew from a previous study that the moths can use the geomagnetic field to navigate, but they only seemed to be able to do so in combination with visual landmarks, so we were thinking about what kind of landmarks these could be," explained Andrea Adden, a researcher at the Francis Crick Institute in the United Kingdom. "If you go to the Australian bush, where these moths live, and look around you at night, one of the most obvious visual landmarks is the Milky Way, which is always visible to some extent, independent of time of night and season," Adden said. "We know that daytime migratory insects use the sun, so testing the starry sky seemed an obvious thing to try." To test whether these moths are truly using the stars to navigate, the researchers captured several using a light-trap. This required the team to traverse into the dark, cold caves where the moths were resting during their migration, which, for some of the team, proved to be too challenging. According to Eric Warrant, a researcher at the University of Lund in Sweden and the leader of the project, "One of the most embarrassing [stories] was when Lena Nordlund from Swedish Radio (who was with us in Australia doing a documentary) asked why I always sent [the] youngsters in the cave and I always sat outside. I was forced to admit I was claustrophobic and was scared of going in — something that of course she included in the documentary." Though Warrant was not comfortable going into the caves, that didn't stop his collaborator, David Dreyer, also a researcher at the University of Lund, from challenging Warrant to a little competition to see who could catch the first Bogong moth of the migratory season. This competition lasted over a decade, with 20 different seasonal opportunities to compete. "[I] dominated this competition, [winning] 19 migratory seasons," Dreyer explained jokingly. "[My] 19 wins would remain unreported, until now. Justice at last." After capturing the moths, the team then placed them in a planetarium-like flight simulator, which included multiple projectors that could be programmed to give specific scenery. The simulator also blocked Earth's magnetic field, forcing the moths to try to navigate in the simulation by their eyesight alone. The researchers also attached electronic sensors to the moths to measure their brain activity. As Bogong moth brains are around the size of a grain of rice, adding the sensors was incredibly time-consuming. "Studying the neural basis of how these moths navigate reveals new processing mechanisms in the insect brain," Adden noted. "Even though human brains and insect brains are obviously very different, it often turns out that the computational principles are remarkably similar, so perhaps we can even learn something from moths that, one day, helps reveal something about the human brain." Once the moths were prepared, the researchers waited for evening in the outback, and then began to test the moths by recording their virtual flight paths in the simulator. "We continued this process until we had used all the prepared moths," Dreyer said. "The following morning was dedicated to data analysis. This routine continued until every moth from the previous catch had been tested — after which we would head out to catch a new batch." While studying the Bogong moths, the COVID-19 pandemic hit Australia, forcing a lockdown. For Adden, this meant being stuck out in the field. "A colleague and I were just wrapping up the field season in early 2020 when Australia entered its first Covid-19 lockdown, and the two of us were locked down at the field station for about a month," she said. "This wasn't as bad as it might seem — with no other humans in sight, we spent our days analyzing data, watching local wildlife and learning to sew." Adden even took the time to practice her astrophotography skills, taking photos of the very night sky her research subjects leveraged to navigate. After years of analysis, the researchers found that the Bogong moths fly in the seasonally appropriate direction (north or south) depending on the stars in the night sky, suggesting that they do in fact use the stars to guide them. "The stars are a very consistent cue. Even though the starry sky rotates throughout the night, the brightest part of the Milky Way is always in the South of the Southern celestial hemisphere," said Adden. "That makes it a very stable compass cue that is reliable not just across nights and seasons, but across centuries." From the moth's brain activity, the team also saw responses specific to certain rotations of the night sky in the flight simulator, and determined that their brains were the most active when they were "flying" in the right direction of their migration. While the Bogong moth is not the only insect to use the stars for guidance, it is the first to do so for long-distance journeys, scientists said. 'A previous study established that dung beetles use the stars to guide short-distance movements, but the beetles only travel a short distance (maybe 5-20 meters) as opposed to flying 1,000 km during a migration,' Ken Lohmann, a researcher at the University of North Carolina, Chapel Hill who was not involved in the study, told Studying how animals like moths navigate is not only fascinating, but can also help ensure the moth populations remain at a healthy level. "The Bogong moth population declined dramatically after the recent drought and 2020 bushfires," explained Adden. "Understanding how their migration works, and which cues they use to navigate, may help us protect these insects, which in turn helps the entire alpine ecosystem of which the moths are an integral part — e.g., as food for pygmy possums and all sorts of birds during the summer months." Part of that conservation work is looking at the role urbanization and, more specifically, light pollution plays in affecting the moths' migratory path. "Light pollution may well be a problem for Bogong moths during their migration,' Adden said. 'On their way from Southern Queensland to the Australian Alps, they pass several major cities, such as Canberra, which can be disorienting and trap the moths. In fact, this happened several years ago, when a cloud of moths briefly took over the Australian Parliament." While the Bogong moth shows the ingenuity of animals, for researchers and conservationists alike, understanding the animal navigation process as a whole is key to understanding their lifestyle, and therefore being able to protect them further. "A central lesson of animal navigation is that species almost always have multiple ways to guide themselves," said Lohmann. This study was published online today (June 18) in the journal Nature.
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15 hours ago
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Tiny Moth Seen Navigating by The Stars in Scientific First
Every year, the bogong moth makes an epic journey across Australia. When the warmer days of spring spread across the country, billions of bogong moths (Agrotis infusa) up stakes and fly, unerringly and only at night, up to 1,000 kilometers (620 miles) to a place they have never been before: the cool caves high in the Australian Alps. There, they will enter a state of dormancy – called aestivation – to wait out the hot summer before dispersing again to breed in autumn, creating the next generation of moths to find their way to the summer caves. Exactly how they accomplish this feat has long fascinated scientists: the lifespan of the bogong is just one year, so the route must be hardwired in somehow. Now, a piece of the puzzle has been found. They follow the stars. "In our study," neuroscientist Andrea Adden of the Francis Crick Institute in the UK told ScienceAlert, "we show that bogong moths can use the starry sky (without any additional cues) to fly in that migratory direction, which tells us that they can use it to navigate: fly in the correct direction stably over many kilometers to a specific migratory goal." The flight of the bogong moths is an amazing thing to experience. They fly for hours through the night, stopping to rest during the day in any crannies and crevices they can access. It's not unheard of for a town to be blanketed with napping bogongs on their way to the Australian Alps; the entire migration can take many nights. To navigate long distances, animals rely on a variety of signs and stimuli. Some may use special adaptations to sense the magnetic field that encompasses the planet. Others may use visual cues, such as following the Moon, the Sun, or landmarks. Previous research led by zoologist David Dreyer and senior author Eric Warrant of Lund University showed that bogong moths use a combination of both magnetoreception and visual cues. It now appears magnetism might not play as big a role as thought. To build on these earlier findings, Dreyer, Adden, Warrant and their colleagues have now conducted a series of experiments to find out what the visual cues in question might be. Using a Helmholtz coil system, which nullifies Earth's magnetic field, they projected different starry vistas onto the vacuum chamber, and observed that the moths still flew in a seasonally appropriate direction. They also showed moths different images of the night sky while Adden recorded their brain activity using single-cell electrophysiology. "A very thin glass electrode (thinner than a human hair) is inserted into specific brain regions of a moth to penetrate the cell-membrane of certain navigation relevant neurons. The signal or electric activity of such a neuron is now amplified and recorded for subsequent analysis," Dreyer explained. "While the cell was impaled, the moth was stimulated with rotations of a projected image of the starry sky and various controls. It turns out that about 28 of the recorded neurons responded to changes of the orientation of the starry sky, not the control image (image in which a randomized arrangement of the starry sky was presented)." That rotation is important, and to understand why, we have to consider another animal that uses the stars as a guide: the dung beetle. Previous research has shown that dung beetles use a mental stellar map to return home after rolling a ball away from the dung heap. But their journey is quite different from the one bogong moths undertake. "Dung beetles don't care where they end up with their dung ball, they roll their ball in a random direction away from competitors on the dung heap," Adden explained. "Also, dung beetles only need to get far enough from the dung heap to eat their meal in peace, a distance they travel in about 10 minutes." The journey of a bogong moth is much longer, taking up to several weeks, for hours at a time, with much higher stakes: if the moth doesn't make it to that cave in time for summer, it's not going to survive into the next breeding season. "It needs to compensate for crosswinds and most importantly, if the bogongs predominantly use their sky compass, they would need to compensate for the celestial rotation over the course of a respective night," Dreyer said. "This means that if bogong moths fly at an angle relative to a particular cue in the sky (for example, the Carina Nebula or the long axis of the Milky Way), this angle would need to change accordingly through steering to keep a straight line of flight." We don't know exactly what stellar properties the moths are basing their navigation on, but the team's research clearly shows that, in the absence of a magnetic field, and under a starry sky, they are still able to find their way. "During our research, we've had two main questions. Firstly, how does the Bogong moth know the direction it needs to travel? And secondly, how does it know when to stop?" Warrant told ScienceAlert. "We are starting to work on the second question now, to determine the sensory cues that might be associated with the destination – this is our next line of research. But another obvious area of future research is to try and understand how magnetic and stellar information is integrated in the brain." Celestial navigation is pretty common in the animal kingdom. Humans do it, some birds can do it, and some seals and frogs. Other moths and butterflies use the Sun to navigate. So it's unlikely that the bogong moth is the only insect that can navigate at night in this way. That, however, does not make it any less of a wonder. "That a tiny insect with a wingspan of 5 cm and a brain the tenth of the volume of a grain of rice manages to fly about 1000 km at nighttime, potentially just by using the stars to steer the course still amazes me," Dreyer said "Imagine someone gives you the task to walk such a distance without food or shelter, exclusively at nighttime without GPS or a compass. If one makes just a small, let's say five-degree, mistake while determining the walking direction on the first night, that means you are already 90 kilometers off target after 1000 kilometers, and if you have to walk on multiple nights, there is plenty of time for steering mistakes. The story doesn't get old." The research has been published in Nature. 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15 hours ago
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Bogong moths appear to use stars to navigate 600-mile journey, a first for insects
Each spring, billions of bogong moths fill southeast Australia's skies. Fleeing the lowlands and trying to beat the heat, they fly roughly 600 miles to caves embedded in the Australian Alps. The moths emerge from their larval stage with the tools to make this journey, but no one knows how the 1-inch-long moths navigate their way to the caves. Scientists previously found that the moths could sense Earth's magnetic field with an internal compass. And now, they say they've cracked the rest of the mystery. In a study published in the scientific journal Nature on Wednesday, researchers found the bogong moths use the starry sky as a guide to the caves. 'The big thing that we've discovered here is a very, very tiny animal like a moth, with a very small nervous system, a very small brain, very small eyes is able to interpret the starry night sky and work out a direction to fly in,' said Eric Warrant, a professor of zoology at Lund University in Sweden, who is an author of the new research. Several bird species, in addition to humans, have demonstrated they can use the stars to navigate great distances. And while dung beetles use the light of stars to travel a few dozen feet, no insect had been documented using stellar navigation to travel. 'The bogong moth, as far as we know, is the first one that has been described to navigate using the stars,' said Andrea Adden, a postdoctoral researcher who studies at The Francis Crick Institute in London and contributed to the research. The researchers discovered the moths' stellar navigation ability by capturing wild bogong moths and then suspending the animals on a thin tungsten rod inside in a small, barrel-shaped 'flight simulator.' With their backs glued to the rod, the animals could flap their wings inside the simulator and turn as if they were flying naturally. 'It can rotate freely,' said David Dreyer, a Lund University researcher who is another author of the study. 'It can choose any direction it wants to fly to.' The researchers created a magnetic vacuum to disable the creatures' internal magnetic compass and focus on its other senses. At the top of the flight simulator, researchers projected an image of the night sky, which could be adjusted as they pleased. During testing, the researchers adjusted the rotation of the sky and found that the moths shifted their flying patterns to compensate and set a new heading. But when the researchers projected a randomized, broken-up sky pattern into the flight simulator, the animals got lost. 'The animals were totally disoriented,' Dreyer said. 'That was, for us, like the final proof, more or less, that they actually indeed use the stars for navigation.' In separate experiments, the researchers cut a tiny window into the moths' brains, inserted a glass tube inside a neuron and measured electrical impulses as the star projection was displayed. The researchers found that electrical impulses spiked when specific angles of the sky were shown. The animals did not react strongly when the researchers projected a randomized sky pattern. Warrant said bogong moth eyes have small pupils and they are likely only capable of seeing a handful of the brightest stars in the sky. The researchers suspect the animals might use the Milky Way to navigate. 'They probably see the Milky Way much more distinctly and brightly than we do,' Warrant said. Warrant said the moths likely use their sense of smell on their final approach to the alpine caves. 'They detect a compound most likely that's coming out of the cave — an odor compound which acts as a kind of an olfactory beacon that guides them into the cave,' he said, adding that the smell is similar to that of rotting meat. The moths, which live for about a year, spend a dormant summer in the caves and then return home to where they emerged. Ken Lohmann, a professor in the biology department at the University of North Carolina who was not involved in the research, said it was convincing work and that the experiments were thoughtful and well controlled. 'One of the things that is really remarkable about it is just the way the moths appear to be able to maintain this heading over a long period of time and over tremendous distances using a relatively small brain,' said Lohmann, who studies animal navigation. 'It just highlights the ingenuity of natural selection.' Bogong moths are endangered and were added to the International Union for Conservation of Nature's 'red list' in 2021. The authors said the new findings could help stem the decline of the species. 'The moth population has been decreasing dramatically in numbers over recent years, especially with the drought and the bushfires that Australia had in 2020,' Adden said. 'Knowing that they use vision as one part of the sensory arsenal that they use to guide their navigation may inform protection approaches with respect to light pollution, for example, when the moths get trapped in cities, for example.' This article was originally published on
