Links for Keyword: Animal Migration

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Domestic chickens use Earth's magnetic field to navigate.

By Jeanna Bryner The jury is still out on why the chicken crossed the road. But new research reveals an inbuilt magnetic compass guides domestic chickens when they do venture across the asphalt and other surfaces. Many animals have an innate sense of direction, finding their way along migration routes that extend thousands of miles. Often, they detect Earth’s magnetic field and use that for orientation. The new study focuses on birds. Study leader Wolfgang Wiltschko of Frankfurt University had been the first to show that migrating European robins rely on the Earth’s magnetic field to navigate during migrations. That finding came more than 40 years ago, and since then a similar magnetic compass has been found in more than 20 bird species, mostly songbirds. Most recently, Wiltschko and his colleagues found domestic chickens are equipped with magnetic sensors that work like compasses. They trained newly hatched chicks of domestic chickens to associate a red ball with their “mother.” At each corner of a pen (where the chicks were kept), designed to correspond to a magnetic North, South, East and West grid, they placed a white screen. Then they hid the ball behind one of the four screens and taught the chicks that the red-ball mother was always behind the screen in the magnetic North corner. © 2007 MSNBC.com © 2007 Microsoft

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: 10480 - Posted: 06.24.2010

Before flying, spiders check weather

Andy Reynolds Spiders love to fly. Hundreds can touch down in an acre of land on a day when conditions are right. And before casting out a silk thread and swooping miles through the air, a spider checks the weather just as a human pilot might do during a pre-flight routine, a new study finds. Spiders somehow consider tradeoffs between wind speed and sunshine, preferring cloudy fall and spring days as the best flight weather, the researchers discovered. Called ballooning, a spider’s mode of transport involves casting out a “dragline” of silk thread, which gets carried by the wind, along with the attached critter. Since wind is the fuel and sunshine leads to updrafts helpful for take-off, scientists figured sunny, windy days would make for perfect ballooning conditions. But a team of biologists and mathematicians with Rothamsted Research in England calculated travel distances under a range of conditions for wind and sun levels. A resulting computer model revealed the best flight weather, from an arachnid's point of view, indeed corresponds with real-life peaks in spider ballooning on cloudy fall and spring days. While hot summer days will spawn more of the updrafts, the associated lack of breeze would mean they couldn’t drift anywhere once aloft, the scientists think. At the other extreme, for instance during winter storms, whipping winds that become too strong would interfere with the updrafts to make any flight impossible. © 2007 MSNBC.com © 2007 Microsoft

Related chapters from BN: Chapter 1: Introduction: Scope and Outlook
Related chapters from MM:Chapter 20:
Link ID: 10181 - Posted: 06.24.2010

Researchers find evidence that sea turtles navigate with magnetic maps

CHAPEL HILL -- Among the most accomplished navigators in the animal kingdom, sea turtles often migrate across thousands of miles of open ocean to arrive at specific feeding and nesting sites. How they do so, however, has mystified biologists for over a century. Now, new findings by a research team headed by Drs. Kenneth and Catherine Lohmann, marine biologists at the University of North Carolina at Chapel Hill, indicate that the navigational ability of sea turtles is based at least partly on a "magnetic map" -- a remarkable ability to read geographic position from subtle variations in the Earth’s magnetic field. Previous work by the group showed that baby sea turtles can use magnetic information as a built-in compass to help guide them during their first migration across the Atlantic Ocean. Their latest studies reveal that older turtles use the Earth’s field in a different, far more sophisticated way: to help pinpoint their location relative to specific target areas, the scientists say. In effect, older turtles have a biological equivalent of a global positioning system (GPS), but the turtle version is based on magnetism.

Migrating Birds Remember Better

Migratory birds not only get to see the world. A new study finds that these globetrotters also have better long-term memories than stay-at-home relatives. The extra brain power could help ensure that the birds don’t get lost on their travels. Birds flying long distances use celestial cues, their sense of smell, and Earth’s magnetic field as rough guides to navigation. As they near their final destination, however, they switch strategies. They look for landmarks such as bushes and trees they have memorized during previous trips. That's how the birds return to the same breeding, wintering, and stopover sites year after year. Anatomical studies suggested that migrants do a lot of learning en route. Garden warblers, for example, return to central Europe from their first trip to Africa with a bigger hippocampus, a region of the brain involved in learning spatial information. Nonmigrating Sardinian warblers, on the other hand, show no such change. But direct evidence that life on the move makes birds remember better was missing. Copyright © 2003 by the American Association for the Advancement of Science.

Related chapters from BN: Chapter 17: Learning and Memory
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Link ID: 3747 - Posted: 06.24.2010

Dawn and dusk dives help tuna find their way

TUNA dive fast and deep twice a day because they use an internal compass to navigate, a new study suggests. It has long been known that tuna dive around dawn and dusk but no one has been quite sure why. To find out, Jay Willis at the University of Tasmania in Hobart, Australia, and colleagues attached tags to 21 southern blue fin tuna (Thunnus maccoyii) and used them to monitor water temperature, time, depth and light levels for 135 days (Behavioral Ecology and Sociobiology, DOI: 10.1007/s00265-009-0818-2). The team found that the tuna initiated these "spike dives" when the sun was precisely 6 degrees below the horizon, 30 minutes before dawn and 30 minutes after sunset. At this time of day magnetic interference created by the solar wind is at its lowest. Since some fish can detect and navigate using magnetic fields, Willis thinks that diving at this time may help tuna to get a clearer magnetic signal. As surface wind and waves also cause interference, Willis suggests that they dive deep to "fine-tune their personal compass". Others are not so sure. "There may be other reasons besides geolocation at work here, namely keeping track of food," says Molly Lutcavage of the University of New Hampshire in Durham. She points out that tuna's prey migrate to depth at around the same time. © Copyright Reed Business Information Ltd.

Brain Recordings Take Flight

By Kelli Whitlock Burton Homing pigeons use landmarks to guide them safely home. But how do the birds track these familiar sites hundreds of meters below as they zip by at 65 kilometers per hour? Scientists are trying to answer that question with a new device that lets them record brain activity as pigeons fly. Exactly how pigeons find their way home is a mystery. While some studies suggest the birds rely on smells, the position of the sun, or Earth's magnetic field to navigate, scientists also know that pigeons use visual landmarks. To see how the pigeons' brains processed these sights, Alexei Vyssotski and colleagues at the University of Zurich in Switzerland developed the Neurologger2, a device that simultaneously tracks the birds' route while also recording brain activity as they fly over familiar sites. Neurologger2 weighs just 2 grams and uses an electroencephalogram to record brain activity. In a study published online this week in Current Biology, the scientists trained 26 pigeons to recognize a loft as their home base. Then, they implanted tiny electrodes on the birds' brains and connected them with Neurologger2. They outfitted the birds with global positioning system monitors and then released them from different points 10 to 30 kilometers away from the loft. Once the birds returned, the researchers removed the devices and compared the record of the birds' brain activity with their positions at the time. Vyssotski found that when the birds flew over landmarks, such as a familiar highway, high-frequency brain waves suddenly got more intense. © 2009 American Association for the Advancement of Science.

Related chapters from BN: Chapter 2: Functional Neuroanatomy: The Cells and Structure of the Nervous System
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Link ID: 12993 - Posted: 06.24.2010

'Magnetic cows' are visible from space

Daniel Cressey Despite thousands of years of coexistence, exploitation and cheese, humanity seems to have missed an intriguing fact about cows: they like to point north. Or possibly south. An analysis of more than 8,000 cows claims they have a statistically significant preference to align themselves in a north-south direction. The team behind this study has also found a similar preference in deer, and believes the animals must be sensing the Earth's magnetic field. While 'magnetoreception' has been documented in insects, birds and some mammals, the idea that such a prominent example of it could have gone unrecognised for years comes as a surprise. What evolutionary advantage, if any, the cattle might accrue is unclear. "It is amazing that this ubiquitous conspicuous phenomenon apparently has remained unnoticed by herdsmen and hunters for thousands of years," write Sabine Begall, of the University of Duisberg-Essen in Germany, and colleagues in Proceedings of the National Academy of Sciences. Begall's team used satellite photos from Google Earth to analyse the orientation of 8,510 cattle at 308 sites around the globe. The photos were chosen to ensure the animals were clearly visible, standing on flat ground, and not close to water or feeding areas that would influence their position. "The whole search was quite time-consuming," says Begall. "Sometimes you find several pastures within minutes, and at other times you search and search without finding anything useful." © 2008 Nature Publishing Group

Guided by the Light

By Rachel Zelkowitz Who needs a GPS when you have, well, whatever migratory birds and sea turtles have? For centuries, humans have marveled at the ability of these and other animals to navigate the globe, in some cases returning to the same breeding spot year after year from as far as 15,000 kilometers away. How they find their way remains a mystery, but new research suggests their prowess may depend on the ability to "see" Earth's magnetic field. Researchers agree that however animals navigate, they use Earth's magnetic field as a guide. Theories about how animals detect these fields, a property called magnetosensitivity, generally fall into two camps. One group argues that tiny crystals of a magnetic mineral known as magnetite, which is found in the brains of some birds and in bacteria, are key. Other scientists say that animals carry photoreceptor molecules that enable them to actually "see" magnetic fields. How these molecules work is not clear, but some researchers think light might destabilize electrons in the photoreceptors, making them susceptible to Earth's magnetic pull. Previous work has shown that animals must be able to respond to blue light to detect magnetic fields, so researchers have eyed cryptochrome, a protein that allows plants and animals to sense blue light, as a likely candidate for the magnetosensitivity photoreceptor. But it's hard to isolate the effects of a single protein in a complex organism. So a team of researchers from the University of Massachusetts Medical School in Worcester swapped small, forgoing migratory birds and other large animals for the humble fruit fly. © 2008 American Association for the Advancement of Science.

Related chapters from BN: Chapter 10: Vision: From Eye to Brain; Chapter 8: General Principles of Sensory Processing, Touch, and Pain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain; Chapter 5: The Sensorimotor System
Link ID: 11852 - Posted: 06.24.2010

Molecular Action May Help Keep Birds on Course

By Rick Weiss Four decades after scientists showed that migratory birds use Earth's magnetic field to orient themselves during their seasonal journeys, researchers have at last found a molecular mechanism that may explain how they do it. The work, described online yesterday in the journal Nature, was conducted in a test tube and does not prove that birds actually use the mechanism. And researchers aligned with a competing model say they are not convinced. But by identifying for the first time a molecule that reacts to very weak magnetic fields, the experiments prove the plausibility of a long-hypothesized method of avian navigation that has had a credibility problem because no one had ever found a molecule with the required sensitivity. "This is a proof of principle that a chemical reaction can act as a magnetic compass," said Peter Hore of the University of Oxford, who with fellow chemist Christiane Timmel led the research. Hore is testing similar molecules, called cryptochromes, isolated from the eyes of migratory birds. Devens Gust, a chemist at Arizona State University who worked with Hore and Timmel, said the molecules "seem to have the right structural and chemical features to allow them to show this effect." © 2008 The Washington Post Company

Homesick crocodiles make epic return swim

Catherine Brahic Far from being lethargic and lazy creatures, crocodiles will travel hundreds of miles to return home, the first satellite-tracking experiment of the reptile has confirmed. Australian scientists tracked three saltwater crocodiles after moving them between 56 and 126 kilometres away from their home territory. The study confirms that the world's largest reptile has a remarkable homing instinct and will cover great distances in order to get home. It also suggests that airlifting problematic crocs to new areas may be ineffective at keeping them away. Aided by crocodile expert and TV presenter Steve Irwin, who died in September 2006, Craig Franklin of the University of Queensland and colleagues captured the three large male saltwater crocodiles (Crocodylus porosus) from coastal areas between August and September 2004. After fitting each with a satellite tracking device, the researchers airlifted each of the animals by helicopter to a new stretch of coastline either 56 km, 99 km or 126 km away. All three animals behaved in roughly the same way. After a few weeks of exploring their new habitats, each set off home, travelling around the coast back to their point of departure, taking between 5 and 20 days to get home. © Copyright Reed Business Information Ltd.

Hard-Wired for Home

By John Bohannon Take a pigeon hundreds of kilometers from its home, and it has no problem finding its way back. For years, scientists have suspected that the bird's stellar navigation has to do with its ability to read Earth's magnetic fields. Now, thanks to a geomagnetic anomaly in New Zealand, researchers have the strongest evidence yet that this is indeed the case. Until now, support for a pigeon's internal compass has been mostly anecdotal. The birds tend to fly in erratic patterns during electrical storms, for example. The first hard evidence for the geomagnetic theory came from a study showing that pigeons could detect a magnetic field in a wind tunnel (ScienceNOW, 24 November 2004), but that field was many times more intense than Earth's. Also, because the field was either completely on or off, it left the question open of how exactly pigeons might use subtle magnetic differences in the wild to correct their trajectories. Taking a more natural approach, a team led by Todd Dennis, a behavioral ecologist at the University of Auckland in New Zealand, released pigeons close to a place called the Auckland Junction Magnetic Anomaly. Here, a cluster of massive rock slabs deep below the surface causes a detectable spike in the geomagnetic field. Dennis reasoned that if the pigeons were released here, they would reveal how they were using geomagnetic information as they struggled to get clear of the anomaly. To keep track of their trajectories, the researchers strapped global positioning system (GPS) devices to the birds' backs. © 2007 American Association for the Advancement of Science

Homing pigeons reveal true magnetism

Michael Hopkin It's official: homing pigeons really can sense Earth's magnetic field. An investigation of their ability to detect different magnetic fields shows that their impressive navigation skills almost certainly relies on tiny magnetic particles in their beaks. The discovery seems to settle the question of how pigeons (Columba livia) have such an impressive 'nose for north'. Some experts had previously suggested that the birds rely on different odour cues in the atmosphere to work out where they are. But the latest findings suggest that they are using magnetic cues. The idea that pigeons' beaks contain tiny particles of an iron oxide called magnetite is not a new one, says Cordula Mora, who led the latest study at the University of Auckland, New Zealand. But the particles themselves are likely to be only a few micrometres across, and no one has ever seen them under the microscope. Mora's behavioural experiments therefore give the best indication yet that pigeons are aware of Earth's magnetic field. She and her colleagues taught the pigeons to discriminate between magnetic fields by placing them in a wooden tunnel with a feeder platform at either end and coils of wire around the outside. ©2004 Nature Publishing Group

Electric Sense Sharper Than Thought

Most animals sniff, listen, and look to learn about the world around them. But weakly electric fish probe their environment using pulses or waves of electricity. Now, scientists have shown that the fish's electric sense is sharper than they'd realized: The fish can judge the shape and orientation of objects using electricity alone. Electric fish get their picture by generating an electric field and checking to see how it gets distorted. Objects that conduct electricity, such as other fish, warp the field differently than, say, rocks do. Scientists think the extra sense aids these stream-dwelling natives of Africa and South America in their nocturnal foraging. Previous work suggested that the fish can use touch and their electric sense to identify shapes. Now, a team of biologists and neuroscientists has shown that electricity alone is enough to size things up. In the 4 May issue of Current Biology, the researchers, led by Christian Graff of the Laboratoire de Biologie du Comportement in Grenoble, France, describe how they put the fish's electric sense to the test. The team trained six fish--three each of two species--to recognize virtual objects created by the interaction of the fish's electric field with electrodes in an aquarium maze. Depending on the pattern of connected electrodes, the fish would detect different arrangements of bars or planes oriented horizontally or vertically. Copyright © 2004 by the American Association for the Advancement of Science.

How sunset helps birds to navigate

Tim Radford, science editor, The Guardian Migrating songbirds check their direction each night before take-off - by taking a bearing on the setting sun. Many migrating creatures - honeybees, certain fish, many birds, and even monarch butterflies - possess built-in compasses to follow the lines of the Earth's magnetic field, and today in the journal Science ornithologists report on how they tried to mislead thrushes by exposing them to magnetic fields distorted towards the east. It seemed to work. Released after dark, the birds flew west instead of north to their summer breeding grounds. They were fitted with radio transmitters, and the German and American ornithologists followed them by car for up to 1,100km (680 miles). However, once free to decide where they were, the birds noted the direction of twilight and corrected their flight northward. The conclusion: thrushes steer by compasses at night, and update them from the setting sun every 24 hours. Guardian Unlimited © Guardian Newspapers Limited 2004

Mole rat's magnetic magic revealed

NewScientist.com news service The blind mole rat continually monitors its direction using the Earth's magnetic field when it makes long underground journeys, new research has revealed. It is first animal discovered to have this talent. Blind mole rats have no eyes and spend most of their time burrowing in subterranean tunnels. They often have to make long journeys from their nests to find food and yet are able to find their way efficiently through complex mazes of tunnels. They use signals such as smell and balance to check their direction and progress over short distances. But scientists have now discovered that on longer routes they combine this information with constant reference checks of the Earth's magnetic field. © Copyright Reed Business Information Ltd.

Dung beetle a marvel of navigation, if not diet

Insect uses moon as nocturnal compass Keay Davidson, Chronicle Science Writer The moon is a quarter of a million miles away, and it may seem irrelevant to the evolution of life on Earth. It isn't totally irrelevant, though: Many a dung beetle owes its survival to the baleful rays of the moon. Without those rays, new research shows, the dung beetle couldn't find its way through nocturnal, predator-haunted terrain. True, you may not care what happens to dung beetles. They are among the more embarrassing members of the insect world, given their taste for, well, excrement; it's a prime source of nutrition for them. Upon finding fecal matter, they roll it into nutritious clumps, which they laboriously push to a safe place. ©2003 San Francisco Chronicle

Related chapters from BN: Chapter 1: Introduction: Scope and Outlook
Related chapters from MM:Chapter 20:
Link ID: 4003 - Posted: 06.24.2010

Mice make their own signposts

First evidence of animal creating markers to navigate. HANNAH HOAG Wood mice fashion portable signposts from bright leaves and shells when they explore fields for food, a new study suggests1. This is the first time that animals other than humans have been found to use moveable landmarks. "No one thought that mice would be clever enough to use tools for navigation," says biologist Pavel Stopka of Charles University in Prague, the Czech Republic. Wood mice live in large fields that often lack features that they might use to locate nests, food sources or danger zones. So the animals build bundles of leaves and twigs as they explore, report Stopka and his colleague, David Macdonald of the University of Oxford, UK. © Nature News Service / Macmillan Magazines Ltd 2003

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Link ID: 3764 - Posted: 06.24.2010

Turtles' epic ocean voyages guided by smell

NewScientist.com news service Seafaring turtles may use smell to navigate during the epic ocean voyages they undertake to reach their breeding grounds, suggests a new satellite-tracking study. Green turtles swim over 2200 kilometres from foraging grounds in Brazil to nest on Ascension Island, which sits in the middle of the Atlantic Ocean. How they find their way has puzzled scientists since Darwin. Now Graeme Hays, at the University of Wales Swansea, and colleagues have shown that sniffing the air is at least part of the answer. The researchers abandoned turtles in the sea 50 kilometres from the island and found that those left downwind returned much more quickly. © Copyright Reed Business Information Ltd.

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Link ID: 3723 - Posted: 06.24.2010

Scientists explore how lobsters find their way

By CATHERINE CLABBY, Staff Writer What do you get when you kidnap lobsters from their home waters, blindfold them and test whether they find their way back? Big news. Animals with brains the size of peas can navigate in places they've never been. Science long assumed that only a handful of creatures, mostly migrating birds, had smarts enough to pull that off. © Copyright 2003, The News & Observer Publishing Company

Light guides flight of migratory birds

Blacksburg, Va. -- Songbirds use multiple sources of directional cues to guide their seasonal migrations, including the Sun, star patterns, the earth's magnetic field, and sky polarized light patterns. To avoid navigational errors as cue availability changes with time of day and weather conditions, these "compass" systems must be calibrated to a common reference. Experiments over the last 30 years have failed to resolve the fundamental question of how migratory birds integrate multiple sources of directional information into a coherent navigational system. Last autumn, Rachel Muheim, a postdoctoral associate in biology professor John Phillips' lab at Virginia Tech, captured Savannah sparrows in the Yukon before they headed south. She was able to demonstrate that the birds calibrate their magnetic compass based on polarized light patterns at sunset and sunrise. The research appears in the Aug. 11, 2006, issue of Science, in the article, "Polarized Light Cues Underlie Compass Calibration in Migratory Songbirds," by Muheim, Phillips, and Suzanne Akesson. Muheim did her Ph.D. work at Lund University in Sweden with Akesson, who made the Alaska trip possible. Polarized light is light that oscillates in one plane relative to the direction of propagation. At sunrise and sunset, there is a band of intense polarized light 90 degrees from the sun that passes directly overhead through the zenith and intersects the horizon 90 degrees to the right and left of the sun. Just as the sun location changes with latitude and the time of year, so does the alignment of the band of polarized light.

Related chapters from BN: Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 9232 - Posted: 08.12.2006

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Links for Keyword: Animal Migration