Links for Keyword: Animal Migration

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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.

Related chapters from BP6e: Chapter 8: General Principles of Sensory Processing, Touch, and Pain
Related chapters from MM:Chapter 5: The Sensorimotor System
Link ID: 10780 - Posted: 06.24.2010

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 BP6e: Chapter 1: Biological Psychology: Scope and Outlook
Related chapters from MM:Chapter 1: An Introduction to Brain and Behavior
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

Related chapters from BP6e: Chapter 19: Language and Hemispheric Asymmetry
Related chapters from MM:Chapter 15: Language and Our Divided Brain
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.

Related chapters from BP6e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
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 BP6e: 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

Listening to the Faint Flutter of Birds Passing in the Night

By TINA KELLEY Who knew there was a noise for this? And not just one noise, but a billionfold chirping, all night long, all spring, all fall, barely audible but as elemental as the grinding of the Earth on its axis. Jeff Wells, an avian ecologist, shared the tiny calls, slightly amplified, at a Nocturnal Bird Migration Concert Friday night at the Prospect Park Audubon Center. A simple high-powered microphone was set up on the center's roof, connected to Dr. Wells' computer, which displayed pictures of birds that migrate through the city at this time of year. He also showed spectrograms, or pictures of their calls as ascending or descending black zigzag ribbons, the audible thumbprint of each species. "I want to let you in on this great secret, a great mystery only a tiny, tiny number of people in the world ever know about," he told a group of about 25 people, his voice hypnotic in its wonderment. "They're all up there in the air, migrating while we sleep, on high highways of wind," said Dr. Wells, the senior scientist at the Boreal Songbird Initiative, a conservation group that tries to protect the endangered boreal, or northern, forest that stretches from Alaska to Newfoundland and is the summer home of three to five billion birds. Copyright 2006 The New York Times Company

Related chapters from BP6e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
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Link ID: 8945 - Posted: 05.22.2006

Tiny tags trace dragonfly paths

The epic journeys taken by dragonflies searching for warmer climates have been revealed by scientists in the US. The team, led by researchers from Princeton University, found that the insects are capable of flying up to 85 miles (137 km) in a day. Writing in the journal Biology Letters, the group describes how it tracked the movements by attaching tiny radio transmitters to the insects. A scientific posse followed the signals from a receiving aeroplane. Other researchers monitored the insects' progress from the ground. The dragonflies' route took them along the east coast of America towards the warmer south. The data revealed that the dragonflies' migration patterns are strikingly similar to those of songbirds, suggesting there is a strong evolutionary link to their behaviours. "Insects have been around far longer than birds, therefore we suspect that they have been migrating far longer than birds," said Professor David Wilcove of Princeton University and one of the authors of the paper. "It is just possible what we are seeing here are the basic primitive rules of migration and that birds converged on the tricks of the trade," he told Science In Action on the BBC World Service. Billions of common green darner dragonflies (Anax junius) migrate every year but until now hardly anything was known about their routes or strategy. (C)BBC

Displaced songbirds navigate in the high Arctic

By experimentally relocating migratory white-crowned sparrows (Zonotrichia leucophrys gambelii) from their breeding area in the Canadian Northwest Territories to regions at and around the magnetic North Pole, researchers have gained new insight into how birds navigate in the high Arctic. In particular, the findings aid our understanding of how birds might determine longitudinal information--a challenging task, especially at the earth's poles. The work is reported in Current Biology by Susanne �kesson and colleagues at Lund University in Sweden. Migratory birds navigating over long distances can determine their latitude on the basis of geomagnetic and celestial information, but longitudinal position is much more difficult to determine. In the new work, researchers investigated whether birds can define their longitude after physical displacements in the high Arctic, where the geomagnetic field lines are steep and the midnight sun makes star navigation impossible for much of the summer. White-crowned sparrows are nocturnally migrating birds that breed in northern Canada and perform long migrations covering a few thousand kilometers to winter in the southern United States. In the study, young and adult white-crowned sparrows were captured with mistnets near Inuvik, NW Territories, Canada, during mid-July to mid-August--the end of the breeding period and shortly before migration--and transported by a Canadian icebreaker along a northeasterly route to nine sites on the tundra, among them the magnetic North Pole (located on Ellef Ringnes Island). The researchers then recorded the birds' directional orientation in cage experiments.

Chickens orient using a magnetic compass

It has been known for some time that many species of birds use the Earth's magnetic field to select a direction of movement--for example, during migration. However, although such birds clearly have a sense of direction, until now it has not been possible to train birds to move in a certain direction in the laboratory, even if they are motivated by a food reward. The reasons for this failure have been perplexing, but researchers now report that they have been able to successfully accomplish this training task, providing new insight into the evolution of magnetic sensing and opening new opportunities for further study of magnetoreception. In the new work, researchers including Rafael Freire from the University of New England (Australia), Wolfgang Wiltschko and Roswitha Wiltschko from the University of Frankfurt, Germany, and Ursula Munro from the University of Technology in Sydney, demonstrated for the first time that birds could be trained to respond to a magnetic direction. The researchers trained domestic chicks to find an object that was associated with imprinting and was behind one of four screens placed in the corners of a square apparatus, and, crucially, showed that the chicks' direction of movement during searching for the hidden imprinting stimulus was influenced by shifting the magnetic field. One important difference between this work and earlier attempts to train birds is that the researchers used a social stimulus to train the birds, whereas most previous attempts have used food as the reward. The authors of the study hypothesize that in nature, birds do not use magnetic signals to find food, and tests involving such a response may be alien to them.

How butterflies fly thousands of miles without getting lost revealed by researchers

Jerusalem -- While "navigation" systems in automobiles are a fairly new (and still costly) innovation, monarch butterflies have managed for millennia to navigate their way for a distance of some 3000 miles (4800 kilometers) each fall from Canada to Mexico (and vice-versa in the spring) without losing their way. The phenomenon of long-range bird migration is a well-known one, but not in the insect world. Also, among birds their migration route is a round-trip one, which they make more than once in their lifetimes, while for the monarch it is strictly a one-way trip for each butterfly. How do these creatures do it? The mystery of the mechanisms involved in this remarkable phenomenon has been resolved by a team of scientists who did this by exploring the infinitesimal butterfly brain and eye tissues to uncover new insights into the biological machinery that directs this delicate creature on its lengthy flight path. The research team, led by Prof. Steven Reppert of the University of Massachusetts Medical School, included Dr. Oren Froy, now of the Faculty of Agricultural, Food and Environmental Quality Sciences of the Hebrew University of Jerusalem. Others involved were from the Czech Academy of Sciences and the University of California, Irvine. Their latest findings were published in a recent issue of Neuron magazine, constituting a continuation of their earlier work, published in the journal Science.

Related chapters from BP6e: Chapter 10: Vision: From Eye to Brain; Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 7: Vision: From Eye to Brain; Chapter 10: Biological Rhythms and Sleep
Link ID: 7723 - Posted: 08.02.2005

Chickadees can help humans get their bearings

How did University of Alberta researchers discover that animals zig when they were only supposed to zag? A little birdie told them. In studying the spatial memory of wild-caught mountain chickadees, University of Alberta researchers were surprised to discover the birds contradicting prior research that showed how animals navigate. This study is the first to reveal a different pattern. Previously, only animals that had been raised in human-made enclosures had been tested. The findings are published in the July issue of Biology Letters. To get their bearings, humans and other animals are often guided by the geometrical shape of their environment. For example, humans have an easy time distinguishing the door located at the ends of a hallway from those located in the middle, but may confuse doors at the two ends, such as when they re-enter a hallway in a hotel. "This has been observed in every species tested, even when landmarks alone could be used, suggesting that animals are predisposed to go by geometry," said co-author Dr. Chris Sturdy, a professor of psychology and member of the Centre for Neuroscience at the University of Alberta.

Whales 'led astray by magnetism'

By Dr David Whitehouse Increased solar activity causing disturbances in the Earth's magnetic field may cause whales to run aground in the North Sea, say researchers. Analysis of whales stranded between 1712 and 2003 shows that more are stranded when solar activity is high. Writing in the Journal of Sea Research, scientists propose that whales use the Earth's magnetic field to assist navigation like homing pigeons do. As the Sun disrupts the magnetic field whales can become confused, they say. The Sun goes through a cycle with an average length of about 11 years, though individual cycle lengths have ranged from 8 to 17 years. Some evidence exists that shorter cycles produce a higher flux of radiation from the Sun. Dr Klaus Vaneslow and colleagues from the University of Kiel have analysed the lengths of solar cycles and find that 87 of the 97 reported sperm whale strandings over the past 300 years in the North Sea region occurred when the length of the Sun's activity cycle was below average. They argue that whales may be like pigeons and dolphins in having a magnetic sense based on small crystals of magnetite found in certain cells. Pigeons use such cells to sense the Earth's magnetic field to help in their navigation. Pigeon enthusiasts are well aware that the birds can go astray during times of high solar activity, when disturbances in the magnetic field confuse them. (C)BBC

How monarch butterflies are wired for navigation

In their extraordinary annual migration from North America to Mexico, monarch butterflies are known to use the angle of polarized sunlight as a celestial guide to help them keep to a straight and true path southward. But details of their navigational machinery have remained a mystery. Now, researchers, led by Steven Reppert of University of Massachusetts Medical School, Ivo Sauman of the Czech Academy of Sciences and Adriana Briscoe of the University of California at Irvine, have explored the infinitesimal butterfly brain to uncover new insights into that machinery. Their findings show that the same ultraviolet light that has become an anathema to cancer-wary humans is critical for butterfly navigation. Also, the researchers were surprised to discover a key wiring connection between the light-detecting navigation sensors in the butterfly's eye and the creature's circadian clock--a critical link if the butterflies are to compensate for the time of day in using their "sun compass." The researchers' techniques include molecular analysis of butterfly brain proteins, as well as flight tests in which the scientists manipulated the light reaching their insect subjects and measured the navigational response. In their studies, the researchers discovered that ultraviolet photoreceptors dominated in the region of the butterfly visual system known to specialize in polarized light detection.

Related chapters from BP6e: Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 7306 - Posted: 05.05.2005

Butterflies 'follow flightpaths'

Butterflies do not flutter aimlessly around the garden but instead follow precise flightpaths, scientists say. A UK team of researchers made the discovery by tracking the insects with radar, using tiny transponders attached to the backs of butterflies. This gave them information on the insects' flightpaths, speeds and foraging behaviour - some of which could guide conservation measures. Details of the research appear in Proceedings of the Royal Society B. "We've never been able to see their flight tracks up to 1km before and it's showing us that they do seem to be quite directive in the way they're flying," said co-author Lizzie Cant of Rothamsted Research in Harpenden, UK. The scientists tagged peacock (Inachis io) and small tortoiseshell (Aglais urticae) butterflies with transponders weighing just 12mg. After checking that the devices did not affect their behaviour, the researchers released 33 insects into a 500x400 sq m field being scanned by radar on the Rothamsted estate. This allowed them to track an individual butterfly at a range of up to about 1km. They successfully recorded the movements of 30 of the insects they released. (C)BBC

Related chapters from BP6e: Chapter 11: Motor Control and Plasticity
Related chapters from MM:Chapter 5: The Sensorimotor System
Link ID: 7167 - Posted: 04.10.2005

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Links for Keyword: Animal Migration