Links for Keyword: Animal Migration

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How Bumblebees and Zebra Fish Navigate Their Worlds

James Gorman All moving animals do their best to avoid running into things. And most living things follow a tried and true strategy — Watch where you’re going! Flying and swimming animals both have to cope with some complications that walkers, jumpers and gallopers don’t confront. Not only do they have to navigate in three dimensions, but they also cope with varying air and water flow. Beyond that, they often do so without the same references points and landmarks we have on the ground. Christine Scholtyssek of Lund University in Sweden, and colleagues decided to compare how two species in different mediums, air and water, which pose similar problems, reacted to apparent obstacles as they were moving. What they found, and reported in Biology Letters in May, was that the two species they examined — bumblebees and zebra fish — have very different strategies. It was known that the bees’ navigation depended on optic flow, which is something like the sensation of watching telephone poles speed past from a seat on a moving train. They tend to fly away from apparent obstacles as they approach them. The question was whether fish would do something similar. So, in order to give both animals the same test, Dr. Scholtyssek and her colleagues devised an apparatus that could contain air or water. When one wall had vertical stripes and the other horizontal, the bees, not surprisingly, flew away from the vertical stripes, which would have appeared as one emerging obstacle after another as the bees flew past. Horizontal stripes don’t change as a creature moves past, so they provide no reference for speed or progress. The fish, however, swam closer to the vertical stripes, which wasn’t expected. “It is surprising that although fish and bees have the same challenge, moving with or against streams, they do not use the same mechanisms,” Dr. Scholtyssek said. © 2014 The New York Times Company

Related chapters from BN: Chapter 8: General Principles of Sensory Processing, Touch, and Pain
Related chapters from MM:Chapter 5: The Sensorimotor System
Link ID: 19778 - Posted: 07.01.2014

Bees build mental maps to get home

Jessica Morrison Bees, like birds and butterflies, use the Sun as a compass for navigation, whereas mammals typically find their way by remembering familiar landmarks on a continuous mental map. However, the latest research suggests that bees also use this type of map, despite their much smaller brain size. The work adds a new dimension to complex bee-navigation abilities that have long captivated researchers. “The surprise comes for many people that such a tiny little brain is able to form such a rich memory described as a cognitive map,” says co-author Randolf Menzel, a neurobiologist at the Free University of Berlin. The research by Menzel and his team, published today in the Proceedings of the National Academy of Sciences1, demonstrates that bees can find their way back to their hives without relying solely on the Sun. Instead, they seem to use a 'cognitive map' that is made up of memorized landscape snapshots that direct them home. The cognitive map used by mammals is thought to originate in the brain’s hippocampus. Humans employ such maps on a daily basis; for example, even in a windowless office, many people can point towards their home, orienting themselves in space based on knowledge of their location relative to the outside world. “They can point to their home generally even though they can’t see it, even along a path through a wall that they haven’t travelled,” explains Fred Dyer, a behavioural biologist at Michigan State University in East Lansing, who was not involved in the research. The study authors argue that bees can do something similar, albeit on a much more rudimentary level. © 2014 Nature Publishing Group

Related chapters from BN: Chapter 8: General Principles of Sensory Processing, Touch, and Pain; Chapter 17: Learning and Memory
Related chapters from MM:Chapter 5: The Sensorimotor System; Chapter 13: Memory and Learning
Link ID: 19684 - Posted: 06.03.2014

Electronics' noise disorients migratory birds

Jessica Morrison Interference from electronics and AM radio signals can disrupt the internal magnetic compasses of migratory birds, researchers report today in Nature1. The work raises the possibility that cities have significant effects on bird migration patterns. Decades of experiments have shown that migratory birds can orient themselves on migration paths using internal compasses guided by Earth's magnetic field. But until now, there has been little evidence that electromagnetic radiation created by humans affects the process. Like most biologists studying magnetoreception, report co-author Henrik Mouritsen used to work at rural field sites far from cities teeming with electromagnetic noise. But in 2002, he moved to the University of Oldenburg, in a German city of around 160,000 people. As part of work to identify the part of the brain in which compass information is processed, he kept migratory European robins (Erithacus rubecula) inside wooden huts — a standard procedure that allows researchers to investigate magnetic navigation while being sure that the birds are not getting cues from the Sun or stars. But he found that on the city campus, the birds could not orient themselves in their proper migratory direction. “I tried all kinds of stuff to make it work, and I couldn’t make it work,” Mouritsen says, “until one day we screened the wooden hut with aluminium.” Mouritsen and his colleagues covered the huts with aluminium plates and electrically grounded them to cut out electromagnetic noise in frequencies ranging from 50 kilohertz to 5 megahertz — which includes the range used for AM radio transmissions. The shielding reduced the intensity of the noise by about two orders of magnitude. Under those conditions, the birds were able to orient themselves. © 2014 Nature Publishing Group,

Related chapters from BN: Chapter 8: General Principles of Sensory Processing, Touch, and Pain; Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 5: The Sensorimotor System; Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 19590 - Posted: 05.08.2014

Displaced pythons display record homing instinct

by Andy Coghlan Burmese pythons can find their way home even if they are taken dozens of kilometres away. It is the first demonstration that big snakes can navigate at all, and far exceeds the distances known to have been travelled by any other snake. At over 3 metres long, Burmese pythons (Python molurus bivitattus) are among the world's largest snakes. For the last two decades they have been eating their way through native species of Florida's Everglades National Park, having been abandoned to the wild by former owners. "Adult Burmese pythons were able to navigate back to their capture locations after having been displaced by between 21 and 36 kilometres," says Shannon Pittman of Davidson College in North Carolina. Pittman and her colleagues caught 12 pythons and fitted them with radiofrequency tags (see video). She released half of them where they were caught, as controls, and transported the other six to distant locations before releasing them. Five pythons made it back to within 5 kilometres of their capture location, and the sixth at least moved in the right direction. The displaced snakes made progress towards their destination most days and seldom strayed more than 22 degrees from the correct path. They kept this up for 94 to 296 days. By contrast, the control snakes moved randomly. On average, displaced snakes travelled 300 metres each day, while control snakes averaged just 100 metres per day. © Copyright Reed Business Information Ltd.

A Salmon Has a Better GPS Than You Do

By Veronique Greenwood Young animals are capable of some pretty astounding feats of navigation. To a species like ours, whose native sense of direction isn’t much to speak of—have you ever seen a human baby crawl five thousand miles home?—the intercontinental odysseys some critters make seem incomprehensible. Arctic tern chicks take part in the longest migration on Earth—more than ten thousand miles (16,000 km)—almost as soon as they fledge. Soon after hatching, young sea turtles take to the waves and confidently paddle many thousands of miles to feeding grounds. Young Chinook salmon likewise make their way from freshwater hatching grounds to specific feeding areas in the open ocean. Biologists know that these species are able to sense things that humans can’t, from the Earth’s magnetic field to extremely faint scents, that could help with navigation. But they may also be inheriting some specific knowledge of the paths they have to follow. A paper in this week’s Current Biology reports that young salmon appear to possess an inborn map of the geomagnetic field that can help them get where they need to go. The researchers, who are primarily based at Oregon State University, performed a series of experiments with Chinook salmon less than a year old that were born and raised in a hatchery and had not yet taken part in a migration. They placed the salmon in pools surrounded by magnetic coils that they could tune to mimic the Earth’s magnetic field at various points in and around the salmons’ feeding grounds. (Kenneth Lohmann at University of North Carolina, Chapel Hill, who has done similar studies that established that baby sea turtles have inborn maps, is also an author of the paper.) © 2014 Time Inc.

Apes plan, announce travel routes, study reveals

Associated Press It's the ape equivalent of Google Maps and Facebook. The night before a big trip, Arno the orangutan plots his journey and lets others know where he is going with a long, whooping call. What he and his orangutan buddies do in the forests of Sumatra tells scientists that advance trip planning and social networking aren't just human traits. A new study of 15 wild male orangutans finds that they routinely plot out their next-day treks and share their plans in long calls, so females can come by or track them, and competitive males can steer clear. The researchers closely followed the males as they traveled on 320 days during the 1990s. The results were published Wednesday in the journal PLoS One. Typically, an orangutan would turn and face in the direction of his route and let out a whoop, sometimes for as long as four minutes. Then he'd go to sleep and 12 hours later set on the heralded path, said study author Carel van Schaik, director of the Anthropological Institute at the University of Zurich. "This guy basically thinks ahead," van Schaik said. "They're continuously updating their Google Maps, so to speak. Based on that, they're planning what to do next." The apes didn't just call once - they kept at it, calling more than 1,100 times over the 320 days. © 2013 The Hearst Corporation

Related chapters from BN: Chapter 19: Language and Lateralization; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 15: Language and Lateralization
Link ID: 18638 - Posted: 09.12.2013

Traveling with elders helps whooping cranes fly straight

By Susan Milius Here’s a lesson on road trips from whooping cranes: For efficient migration, what matters is the age of the oldest crane in the group. These more experienced fliers nudge youngsters away from going off course on long flights. “The older birds get, the closer they stick to the straight line,” says ecologist Thomas Mueller of the University of Maryland in College Park, who crunched data from 73 Grus americana migrating between Wisconsin and Florida. One-year-olds traveling with other birds of the same age, the analysis says, tend to deviate about 76 kilometers from a direct route. But if they fly in a group with an 8-year-old crane, they stray 38 percent less, or about 47 kilometers, Mueller and his colleagues report in the August 30 Science. Eight years of data on these endangered cranes summering in Wisconsin’s Necedah National Wildlife Refuge offered a rare chance to parse how birds find their way. Conservationists have been rebuilding this eastern migratory population of the once widespread birds. Researchers release captive-bred cranes in Wisconsin and lead each class of newbies, just once, with an ultralight aircraft to Florida’s Chassahowitzka National Wildlife Refuge for the winter. Cranes navigate back to Wisconsin on their own. © Society for Science & the Public 2000 - 2013

Related chapters from BN: Chapter 17: Learning and Memory
Related chapters from MM:Chapter 13: Memory and Learning
Link ID: 18591 - Posted: 08.31.2013

Caterpillar does not look where it leaps

By Ella Davies Reporter, BBC Nature An unusual caterpillar uses the sun to navigate as it jumps to safety, according to scientists. The larva of Calindoea trifascialis, a species of moth native to Vietnam, wraps itself in a leaf before dropping to the forest floor. It then spends three days searching for a suitable place to pupate, despite not being able to see out of its shelter. Experts found the insect used a piston-like motion to jump away from strong sunlight. "We believe the object of the jumping is to find shade - to avoid overheating and desiccation," explained Mr Kim Humphreys from the Royal Ontario Museum, Canada who conducted the research alongside Dr Christopher Darling. Their findings are published in the Royal Society journal Biology Letters. Although Mr Humphreys described the caterpillar as "non-descript" in appearance, he said its behaviour makes it unique in a number of ways. "Caterpillars or larvae that jump are rare in themselves," he said. "[This] caterpillar is remarkable for its jumping, which no other insect does in this way. It also makes its own vehicle [or] shelter to jump in." "It is also the only one I know of that jumps in an oriented way." BBC © 2013

Related chapters from BN: Chapter 10: Vision: From Eye to Brain; Chapter 11: Motor Control and Plasticity
Related chapters from MM:Chapter 7: Vision: From Eye to Brain; Chapter 5: The Sensorimotor System
Link ID: 18539 - Posted: 08.21.2013

Beak-to-Brain Nerve May Help Birds Navigate

by Katia Moskvitch In the days before GPS, we needed both a compass and a map to navigate. Migrating birds are no different. Studies have suggested that the animals rely on an internal map and compass to traverse large distances, though just where these senses reside is unclear. Now, scientists say they have the strongest evidence yet that map sense is associated with the beak. Researchers have long suspected that migrating birds navigate by sensing Earth's magnetic field. The idea was that their beaks, which contain a lot of iron, worked like real magnets, with the metal aligning itself relative to the field. Supposedly, the so-called trigeminal nerve transmitted this information to the brain. But in 2009, a team led by Henrik Mouritsen of the University of Oldenburg in Germany cut the trigeminal nerve in several European robins and found that the animals still oriented perfectly. In lab-based experiments, the birds were able to locate the natural and artificial magnetic north. It seemed that the beak played no role in the compass sense. The finding gave support to another hypothesis, one that suggested that the inner compass was instead a magnetism-sensing chemical reaction in the birds' eyes. But Mouritsen's team was still convinced that the beak had to be involved in the magnetosense in some way, and it decided to do another test. In 2010 and 2011, the scientists captured 57 Eurasian reed warblers near Kaliningrad, Russia. Every spring, these birds migrate northeast to their breeding grounds in southern Scandinavia, up to 1000 kilometers away. Once again, the scientists snapped the trigeminal nerve, in half of the birds. But then they also moved all 57 birds 1000 kilometers to the east, where the magnetic field differs from their home site, and released them. © 2010 American Association for the Advancement of Science

Monarch butterflies navigate with compass but no map

Ed Yong Every autumn, millions of monarch butterflies (Danaus plexippus) converge on a small cluster of Mexican mountains to spend the winter. They have journeyed for up to 4,000 kilometres from breeding grounds across eastern North America. And according to a study, they accomplish this prodigious migration without ever knowing where they are relative to their destination. The monarchs can use the position of the Sun as a compass, but when Henrik Mouritsen, a biologist at the University of Oldenburg in Germany, displaced them by 2,500 kilometres, he found that they did not correct their heading. “People seemed to assume that they had some kind of a map that allowed them to narrow in on a site a few kilometres across after travelling several thousands of kilometres,” he says. Now, “it is clear that they don’t”. His results are published in the Proceedings of the National Academy of Sciences1. For more than five decades, scientists have teamed up with amateurs to tag and monitor free-flying monarchs, creating a database of their migrations. When Mouritsen analysed these records, he realized that the monarchs tend to spread out over the course of their migration. Their distribution was a good fit with the predictions of a mathematical model that assumed that the monarchs were flying with just a compass, rather than a compass and a map. Mouritsen also captured 76 southwesterly flying monarchs from fields near Guelph in Ontario, Canada, and transported them 2,500 kilometres to the west, to Calgary in the Canadian province of Alberta. He placed the butterflies in a “flight simulator” — a plastic cylinder that kept them from seeing any landmarks except the sky — and tethered them to a rod that let them point in any direction without actually flying away. © 2013 Nature Publishing Group

Dung Beetles Navigate by the Milky Way

by Gretchen Cuda Kroen A day in the life of a male dung beetle goes something like this: Fly to a heap of dung, sculpt a clump of it into a large ball, then roll the ball away from the pile as fast as possible. However, it turns out that the beetles, who work at night, need some sort of compass to prevent them from rolling around in circles. New research in Current Biology suggests that the insects use starlight to guide their way. Birds, seals, and humans also use starlight to navigate, but this is the first time it's been shown in an insect. The whole point of rolling dung is to impress the female beetle with provisions—i.e., excrement—for her future progeny and entice her to mate. She then lays an egg in the ball and buries it in a network of tunnels more than a meter deep, where it serves as food for the developing larvae inside. But rolling dung balls in a straight line is also key to the male dung beetle's reproductive success. Rival males have been known to overtake a slower moving insect and claim the hard-earned treasure as their own. Competition is fiercest near the dung heap, so making a quick and efficient getaway is crucial for mating success. The discovery that dung beetles use starlight "was an accident more than anything," explains study author Eric Warrant, professor of zoology at the Lund University in Sweden. His research group was studying how the beetles used the polarized light patterns of the moon to stay on their paths, when one moonless night they made a surprising observation—the beetles maintained straight trajectories. "Even without the moon—just with the stars—they were still able to navigate," Warrant says. "We were just flabbergasted." © 2010 American Association for the Advancement of Science

Related chapters from BN: Chapter 11: Motor Control and Plasticity; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 5: The Sensorimotor System
Link ID: 17714 - Posted: 01.26.2013

No GPS Needed: Bumblebees Find Their Own Flight Paths

by Virginia Morell Bumblebees foraging in flowers for nectar are like salesmen traveling between towns: Both seek the optimal route to minimize their travel costs. Mathematicians call this the "traveling salesman problem," in which scientists try to calculate the shortest possible route given a theoretical arrangement of cities. Bumblebees, however, take the brute-force approach: For them, it's simply a matter of experience, plus trial and error, scientists report in the current issue of PLoS Biology. The study, the first to track the movements of bumblebees in the field, also suggests that bumblebees aren't using cognitive maps—mental recreations of their environments—as some scientists have suggested, but rather are learning and remembering the distances and directions that need to be flown to find their way from nest to field to home again. A team of researchers from Queen Mary, University of London outfitted seven bumblebees with tiny radar transponders, which they stuck on the bees' backs with double-sided tape. They trained the bees to forage nectar from five blue artificial flowers (see video). Each artificial flower had a yellow landing platform and a single drop of sucrose, just enough to fill one-fifth of a bumblebee's tank capacity, to ensure that the bees would visit all five flowers on each foraging bout. The scientists placed the flowers in a field at Rothamsted Research, a biological research station north of London, in October—a time of year when there are few natural sources of nectar and pollen and the bees are more likely to focus on the artificial flowers. They arranged the flowers in a pentagon and spaced them 50 meters apart; that distance is more than three times as far as bumblebees can see, so the bees must actively fly around to locate their next target. A motion-triggered Webcam was attached to each flower to record the bees' visits. Then, every day for a month, each bee was freed to forage for 7 hours. © 2010 American Association for the Advancement of Science

A Big Magnet in a Small Fish

by Sarah C. P. Williams After spending 3 years at sea and traveling up to 300 kilometers away from home, a rainbow trout can swim straight back to its original hatching ground, following freshwater streams inland and rarely heading in the wrong direction. This remarkable feat of navigation likely relies on many senses; the fish have superb eyesight and smell. But the trout also seem to rely on Earth's magnetic fields, which point them in the right direction. Now, for the first time in any animal, scientists have isolated magnetic cells in the fish that respond to these fields. The advance may help researchers get to the root of magnetic sensing in a variety of creatures, including birds. "We think this will really be a game changer," says Michael Winklhofer, an earth scientist at Ludwig Maximilians University Munich in Germany who led the new study. "To study magnetic sensory cells, you have to be able to get hold of them first, and that's what we've finally developed a way to do." Previous research has shown that many species of fish, as well as migratory birds, have the ability to detect differences in magnetic field strengths, which vary around the globe. Scientists think that the key to this ability is magnetite, the most magnetic of all minerals, which they've found embedded in bird and fish tissues. They've even narrowed down which tissues in these animals could contain magnetite by using dyes that bind to the mineral. But they've never been able to isolate individual cells that contain magnetite, and some of the staining methods have led to false positives and controversy in the field. © 2010 American Association for the Advancement of Science

How Do Octopuses Navigate?

By Jason G. Goldman Getting around is complicated business. Every year, animals traverse miles of sky and sea (and land), chasing warmth or food or mates as the planet rotates and the seasons change. And with such precision! Some animals rely on visual landmarks, others on subtle changes in magnetic fields, and yet others match their internal clocks with the movement of the sun and stars across the sky. One researcher, Jennifer A. Mather, wondered: how do octopuses navigate? Do they rely on chemotactile sensory information, or do they orient towards visual landmarks? Octopuses occupy “homes” for several days or in some instances for several weeks, and when they go out looking for food, they are sometimes gone for several hours at a time. Therefore, they must use some sort of memory to find their way back home. Many molluscs use trail-following, and follow their own mucus trails, or the trails of others. You might expect that octopuses use trail-following as well, since they forage by using chemotactile exploration – at least four different types of receptors on their suckers gather chemical and tactile information as they move along the rocky seafloor. However, many other species use visual scene recognition to aid in navigation: ants, bees, gerbils, hamsters, pigeons, and even humans, use visual landmarks to navigate around their environments. Since octopuses use visual information to distinguish among different objects, they could use visual landmarks to get home as well. © 2012 Scientific American

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell; Chapter 7: Vision: From Eye to Brain
Link ID: 16843 - Posted: 05.26.2012

Magnetic fields light up 'GPS neurons', scientists say

By Jason Palmer Science and technology reporter, BBC News Researchers have spotted a group of 53 cells within pigeons' brains that respond to the direction and strength of the Earth's magnetic field. The question of how birds navigate using - among other signals - magnetic fields is the subject of much debate. These new "GPS neurons" seem to show how magnetic information is represented in birds' brains. However, the study reported by Science leaves open the question of how they actually sense the magnetic field. David Dickman of the Baylor College of Medicine in the US set up an experiment in which pigeons were held in place, while the magnetic field around them was varied in its strength and direction. Prof Dickman and his colleague Le-Qing Wu believed that the 53 neurons were candidates for sensors, so they measured the electrical signals from each one as the field was changed. Every neuron had its own characteristic response to the magnetic field, with each giving a sort of 3-D compass reading along the familiar north-south directions as well as pointing directly upward or downward. BBC © 2012

Pigeon navigation finding called off-course

By Susan Milius Scientists may have been going in the wrong direction to find bird beaks’ built-in navigation sensors, says a provocative new study. Pigeons and other birds appear to use the Earth’s magnetic field, along with sights and sounds, to figure out where they’re flying. But the widely accepted identification of one set of magnetically sensitive cells is “totally wrong,” says neuroscientist David Keays of the Research Institute of Molecular Pathology in Vienna. He’s talking about work published in 2003 identifying clusters at six places in pigeons’ upper beaks as nerve cells. Those clusters have little crystals of iron compounds that might serve as biological compass needles, the earlier study proposed. For the new study, Keays and his colleagues looked for these cells in about 250,000 thin slices of tissue from beaks of more than 200 pigeons collected across Europe. Clusters of beak cells do contain iron, but it turns out that they’re not consistent in abundance or location, and most aren’t nerve cells at all, he says. Instead, they’re immune system cells called macrophages, he and his colleagues report online April 11 in Nature. “If that’s true, this could be really important,” says neuroethologist Henrik Mouritsen of Carl von Ossietzky University of Oldenburg in Germany. Discarding the old identification of beak sensors would mean researchers have to start from scratch looking for them. © Society for Science & the Public 2000 - 2012

Dirty Dancing: Dung Beetles Get Down to Walk the Line

By Ferris Jabr As a dung beetle rolls its planet of poop along the ground it periodically stops, climbs onto the ball and does a little dance. Why? It's probably getting its bearings. A series of experiments published in the January 18 issue of PLoS ONE shows that the beetles are much more likely to perform their dance when they wander off course or encounter an obstacle. Until now, no one had any idea what a jitterbugging dung beetle was up to. Emily Baird of Lund University in Sweden and her colleagues study how animals with tiny brains—such as bees and beetles—perform complex mental tasks, like navigating the world. The dung beetle intrigues Baird because it manages to roll its dung ball in a perfectly straight line, even though it pushes the ball with its back legs, its head pointed at the ground in the opposite direction. If the six-legged Sisyphus can't see where it's going, how does it stay on its course? Every now and then, a dung beetle stops rolling, mounts its ball and pirouettes. Baird noticed that dung beetles do not dance as often in the lab, where they roll around on flat surfaces, as they do in the field, where the terrain is rough and rocks and clumps of grass often obstruct the beetles' paths. She guessed that by climbing onto a ball of dung four or five times its height, a beetle gets a pretty good vantage point from which to correct any navigational mistakes. But it was only an intuition—she needed evidence. © 2012 Scientific American

Related chapters from BN: Chapter 6: Evolution of the Brain and Behavior; Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 0: ; Chapter 7: Vision: From Eye to Brain
Link ID: 16274 - Posted: 01.21.2012

DNA to flutter by: Monarchs’ genetic instructions help meet migration, navigation needs

By Tina Hesman Saey Scientists have deciphered the complete genetic instruction book of monarch butterflies. It is the first butterfly genome completed and the first of a long-distance migrating insect. Within the butterfly’s genetic archive, neurobiologist Steven Reppert of the University of Massachusetts Medical School in Worcester and his colleagues found genes that may help the insects sense the position of the sun and navigate to fir trees in Mexico, where they spend the winter. Reporting in the Nov. 23 Cell, the team also notes that monarchs make more of certain small genetic molecules, called microRNAs, that are involved in building muscle, regulating temperature sensitivity and storing fat when in migration mode. The 273 million DNA units that make up the monarch genome also include a complete set of genes for producing juvenile hormone, which summer butterflies use to kick-start reproduction. Migrating male monarchs use different strategies than females do to turn off the hormone, the team discovered. Monarchs have genes similar to ones that silk moths use to sense mating chemicals called pheromones. Those genes may aid social interactions between monarchs in their wintering grounds, Reppert says. The scientists also unearthed from the genome a gear previously thought to be missing from the butterfly’s daily, or circadian, clock, which helps the monarchs maintain a straight path. © Society for Science & the Public 2000 - 2011

Related chapters from BN: Chapter 8: General Principles of Sensory Processing, Touch, and Pain; Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 5: The Sensorimotor System; Chapter 10: Biological Rhythms and Sleep
Link ID: 16082 - Posted: 11.26.2011

The mystery of the magnetic cows

Daniel Cressey In 2008, the world’s media was captivated by a study apparently showing that cows like to align themselves with magnetic fields. But attempts to replicate this finding have left two groups of researchers at loggerheads, highlighting the problems faced by scientists working to replicate unusual findings based on new methods of data analysis. Magneto-reception has been detected in animals from turtles to birds. Three years ago, Hynek Burda, a zoologist at the University of Duisburg-Essen, Germany, and his colleagues added cattle to the magnetic family with a paper in Proceedings of the National Academy of Sciences. The team used data from Google Earth to show that domestic cattle seem to prefer to align their bodies along Earth’s magnetic field lines1, and showed a similar phenomenon in field observations of deer. A follow-up study by Burda and his colleagues showed no such alignment near electric power lines, which might be expected to disrupt magneto-sensing in cattle2. Cow conundrum Earlier this year, a group of Czech researchers reported their failed attempt to replicate the finding using different Google Earth images3. The Czech team wrote in the Journal of Comparative Physiology A: “Two independent groups participated in our study and came to the same conclusion that in contradiction to the recent findings of other researchers, no alignment of the animals and of their herds along geomagnetic field lines could be found.” © 2011 Nature Publishing Group,

Crittervision: Turtles surf the magnetic ocean

by Caroline Williams The idea that animals can navigate using their own internal compass is so startling it was once dismissed as pure fantasy. Now there is good evidence that many species - including pigeons, sea turtles, chickens, naked mole rats and possibly cattle - can detect the Earth's geomagnetic field, sometimes with astonishing accuracy. Young loggerhead turtles, for example, read the Earth's magnetic field to adjust the direction in which they swim. They seem to hatch with a set of directions, which, with the help of their magnetic sense, ensures that they always stay in warm waters during their first migration around the rim of the North Atlantic. Over time they build a more detailed magnetic map by learning to recognise variations in the strength and direction of the field lines, which are angled more steeply towards the poles and flatter at the magnetic equator. What isn't known, however, is how they sense magnetism. Part of the problem is that magnetic fields can pass through biological tissues without being altered, so the sensors could, in theory, be located in any part of the body. What's more, the detection might not need specialised structures at all, but may instead be based on a series of chemical reactions. Even so, many researchers think that magnetic receptors probably exist in the head of turtles and perhaps other animals. These might be based on crystals of magnetite, which align with the Earth's magnetic field and could pull on some kind of stretch receptor or hair-like cell as it changes polarity. The mineral has already been found in some bacteria, and in the noses of fish like salmon and rainbow trout, which also seem to track the Earth's magnetic field as they migrate. © Copyright Reed Business Information Ltd.

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