MIGHT BE FACING SOUTH
Cattle shown to align north-south
BY Elizabeth Mitchell / 25 August 2008
Have you ever noticed that herds of grazing animals all face the same way? Images from Google Earth have confirmed that cattle tend to align their bodies in a north-south direction. Wild deer also display this behaviour – a phenomenon that has apparently gone unnoticed by herdsmen and hunters for thousands of years. In the Proceedings for the National Academy of Sciences, scientists say the Earth’s magnetic fields may influence the behaviour of these animals. The Earth can be viewed as a huge magnet, with magnetic north and south situated close to the geographical poles. Many species – including birds and salmon – are known to use the Earth’s magnetic fields in migration, rather like a natural GPS.
A few studies have shown that some mammals – including bats – also use a “magnetic compass” to help their sense of direction. Dr Sabine Begall, from the University of Duisburg-Essen, Germany, has mainly studied the magnetic sense of mole rats – African animals that live in underground tunnels. “We were wondering if larger animals also have this magnetic sense,” she told BBC News. Dr Begall and colleagues first decided to study the natural behaviour of domestic cattle. The researchers surveyed Google Earth images of 8,510 grazing and resting cattle in 308 pasture plains across the globe. “Sometimes it took hours and hours to find some pictures with good resolution,” said Dr Begall. The scientists were unable to
distinguish between the head and rear of the cattle, but could tell that the animals tended to face either north or south.
Their study ruled out the possibility that the Sun position or wind direction were major influences on the orientation of the cattle. Dr Begall said: “In Africa and South America, the cattle (were) shifted slightly to a more north-eastern-south-western direction. “But it is known that the Earth’s magnetic field is much weaker there,” she explained. The researchers also recorded the body positions of 2,974 wild deer in 277 locations across the Czech Republic. Their fieldwork revealed that the majority of grazing and resting deer face northward. About one-third of the deer faced southward. “That might be some kind of anti-predatory behaviour,” speculated Dr Begall.
Willy Miller – a Scottish cattle farmer – remarked: “I’ve never noticed that my cows all face the same way.” Cows are social animals: “[They] all sit down before it rains [and] huddle together in a circle formation during blizzards. But from a cow’s point of view, that’s just sensible,” he told BBC News. Professor John Phillips, a sensory biologist from Virginia Tech University, US, commented that this sixth magnetic sense might be “virtually ubiquitous in the animal kingdom”. He added: “We need to think about some really fundamental things that this sensory ability provides in animals.” The challenge remains for scientists to explain how the animals behave in this way – and if Scottish cattle are the exception to the rule!
email : sabine.begall [at] uni-due [dot] de
“The work, based on a comparison of whale genes, also offers firm support for the theory that all whales descended from the group of hooved, plant-eating land animals called ungulates. The study presents the cow as possibly the closest terrestrial relative of the whale.”
WHALES GET LOST DURING SOLAR STORMS
Whales ‘led astray by magnetism’
BY Dr David Whitehouse / 13 May, 2005
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 eight to 17 years. Some evidence exists to suggest that shorter cycles produce a higher flux of radiation from the Sun. Dr Klaus Vanselow and colleagues from the University of Kiel have analysed the lengths of solar cycles and have found 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.
“It may be the same for whales,” Dr Vanselow told the BBC News website. “Sperm whales migrate long distances with very little visual clues as to where they are going. It would be unsurprising if they too had a magnetic sense. “We believe that our research showing that more whales are beached during times when the Sun disrupts the Earth’s magnetic field makes it a strong possibility that they do. The numbers of cetacean – whale, dolphin and porpoise – strandings around the UK have doubled over the last 10 years. Marine mammal experts say an increase in fishing activity, which leads to more “by-catch”, is a major cause of the problem. Campaigners also claim increased noise in the oceans, coming from ships’ engines and sonar, is a significant factor in whales losing their way.
email : vanselow [at] ftz-west.uni-kiel [dot] de
SHARKS SWIM in LONG STRAIGHT LINES
Sharks respond to magnetic lines
Marine biologists have confirmed sharks can detect changes in magnetic fields. This ability has long been suspected by researchers who have observed the fish migrating huge distances in the ocean along straight lines. A Hawaii University team has trained captive sharks to swim over targets in their tank whenever an artificial magnetic field is activated. The new study, by Dr Carl Meyer and colleagues, is reported in Interface, a journal of the UK’s Royal Society. “This significant advance in demonstrating the existence of a ‘compass’ sense should now make it possible to investigate exactly how this sense works and how sensitive sharks are to the Earth’s magnetic field,” the team tells Interface. The Hawaii group used six sandbar sharks and one scalloped hammerhead in their research. They kept the animals in a 7m-diameter tank. The fish were trained to associate the presence of food in a 1.5m by 1.5m target area on the enclosure floor with the switching on of a magnetic field, derived from a copper coil surrounding the tank.
In a series of trials, the field was then activated at random times and the fish were seen to move on the feeding zone even when there was no food present, proving the existence of their “compass”. “Activating the artificial field produced an immediate response in the conditioned sharks,” the team says. “They changed from swimming steadily around the perimeter of the tank to swimming faster, turning rapidly and converging on the target in anticipation of a food reward.” Tiger sharks, blue sharks and scalloped hammerhead sharks are all known to swim in straight lines for long periods across hundreds of kilometres of open ocean, and then later orient themselves to underwater mountains, or seamounts, where geomagnetic anomalies exist. Scientists want to understand how sharks are able to detect magnetic fields. Other animals that do it, such as trout and pigeons, possess the iron mineral magnetite in their bodies. Sharks, however, do not possess magnetite. It is possible electro-receptors in their heads are employed instead.
email : carlm [at] hawaii [dot] edu
COWS + DEER STUDY
Magnetic alignment in grazing and resting cattle and deer
by 1. Sabine Begall*,†, 2. Jaroslav Červený‡,§, 3. Julia Neef*, 4.
Oldřich Vojtčch‡,¶, and 5. Hynek Burda*
“We demonstrate by means of simple, noninvasive methods (analysis of satellite images, field observations, and measuring “deer beds” in snow) that domestic cattle (n = 8,510 in 308 pastures) across the globe, and grazing and resting red and roe deer (n = 2,974 at 241 localities), align their body axes in roughly a north–south direction. Direct observations of roe deer revealed that animals orient their heads northward when grazing or resting. Amazingly, this ubiquitous phenomenon does not seem to have been noticed by herdsmen, ranchers, or hunters. Because wind and light conditions could be excluded as a common denominator determining the body axis orientation, magnetic alignment is the most parsimonious explanation. To test the hypothesis that cattle orient their body axes along the field lines of the Earth’s magnetic field, we analyzed the body orientation of cattle from localities with high magnetic declination. Here, magnetic north was a better predictor than geographic north. This study reveals the magnetic alignment in large mammals based on statistically sufficient sample sizes. Our findings open horizons for the study of magnetoreception in general and are of potential significance for applied ethology (husbandry, animal welfare). They challenge neuroscientists and biophysics to explain the proximate mechanisms.”
1. *Department of General Zoology, Faculty of Biology and Geography, University of Duisburg-Essen, 45141 Essen, Germany;
2. §Institute of Vertebrate Biology, Academy of Sciences of the Czech Republic, 60365 Brno, Czech Republic;
3. ‡Department of Forest Protection and Wildlife Management, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences, 16521 Praha 6, Czech Republic; and
4. ¶Sumava National Park Administration, Susicka 399, 341 92 Kasperske Hory, Czech Republic
1. Edited by Simon A. Levin, Princeton University, Princeton, NJ, and approved July 17, 2008 (received for review April 15, 2008)
“A suggestion for a case study: Strap a bunch of digital compasses onto grazing cattle, record results.”
COW MAGNETS (UNRELATED)
What are cow magnets?
“Cow magnets are popular with dairy farmers and veterinarians to help prevent Hardware Disease in cattle. While grazing, cows eat everything from grass and dirt to nails, staples and bits of bailing wire (referred to as tramp iron). Tramp iron tends to lodge in the honeycombed walls of the reticulum, threatening the surrounding vital organs and causing irritation and inflammation, known as Hardware Disease. The cow loses her appetite and decreases milk output (dairy
cows), or her ability to gain weight (feeder stock). Cow magnets help prevent this disease by attracting stray metal from the folds and crevices of the rumen and reticulum. One magnet works for the life of the cow!”
by Dr Stephen Juan
“Do humans have a compass in their nose?”
Asked by Lee Staniforth of Manchester, UK
Some years ago scientists at CALTECH (California Institute of Technology in Pasadena) discovered that humans possess a tiny, shiny crystal of magnetite in the ethmoid bone, located between your eyes, just behind the nose. Magnetite is a magnetic mineral also possessed by homing pigeons, migratory salmon, dolphins, honeybees, and bats. Indeed, some bacteria even contain strands of magnetite that function, according to Dr Charles Walcott of the Cornell Laboratory of Ornithology in Ithaca, New York, “as tiny compass needles, allowing them [the bacteria] to orient themselves in the earth’s magnetic field and swim down to their happy home in the mud”.
It seems that magnetite helps direction finding in animals and helps migratory species migrate successfully by allowing them to draw upon the earth’s magnetic fields. But scientists are not sure how they do this. In any case, when it comes to humans, according to some experts, magnetite makes the ethmoid bone sensitive to the earth’s magnetic field and helps your sense of direction. Some, such as Dr Dennis J Walmsley and W Epps from the Department of Human Geography of the Australian National University in Canberra writing in Perceptual and Motor Skills as far back as in 1987, have even suggested that this “compass” was helpful in human evolution as it made migration and hunting easier.
SEE ALSO :
Evidence of a nonlinear human magnetic sense.
BY Carrubba S, Frilot C 2nd, Chesson AL Jr, Marino AA.
Department of Orthopedic Surgery, Louisiana State University Health
Sciences Center, P.O. Box 33932, 1501 Kings Highway, Shreveport, LA
“Human subjects respond to low-intensity electric and magnetic fields.
If the ability to do so were a form of sensory transduction, one would
expect that fields could trigger evoked potentials, as do other
sensory stimuli. We tested this hypothesis by examining
electroencephalograms from 17 subjects for the presence of evoked
potentials caused by the onset and by the offset of 2 G, 60 Hz (a
field strength comparable to that in the general environment). Both
linear (time averaging) and nonlinear (recurrence analysis) methods of
data analysis were employed to permit an assessment of the dynamical
nature of the stimulus/response relationship. Using the method of
recurrence analysis, magnetosensory evoked potentials (MEPs) in the
signals from occipital derivations were found in 16 of the subjects
(P<0.05 for each subject). The potentials occurred 109-454 ms after
stimulus application, depending on the subject, and were triggered by
onset of the field, offset of the field, or both. Using the method of
time averaging, no MEPs were detected. MEPs in the signals from the
central and parietal electrodes were found in most subjects using
recurrence analysis, but no MEPs were detected using time averaging.
The occurrence of MEPs in response to a weak magnetic field suggested
the existence of a human magnetic sense. In distinction to the evoked
potentials ordinarily studied, MEPs were nonlinearly related to the
stimulus as evidenced by the need to employ a nonlinear method to
detect the responses.”
MAGNETIC SIXTH SENSE
We know about the world through our five senses – sight, sound, touch,
smell and taste. But what if there is a 6 th sense? Maybe there is –
the magnetic sense.
by Karl S. Kruszelnicki / 05 July 2000
We know about the world through our five senses – sight, sound, touch,
smell and taste. But what if there is a 6 th sense? Maybe there is –
the magnetic sense.
This magnetic sense seems to be powered by the first new substance
found in the human body since the early medical anatomists made the
startling discovery that we are made of “blood, guts and bones”. There
are tiny magnets, as well, in the human brain – and these magnets can
stop you from getting lost. We’ve known about magnets for a long time. Thousands of years ago, the ancient Chinese and Greeks knew that a black rock called magnetite (Fe304) had magnetic properties. The early ocean-going navigators called it the lodestone – lode is an ancient British word meaning “path” or “way”.
In the year 1600, William Gilbert, who was also the physician to Queen
Elizabeth I of England, published a thesis called ‘On the Magnet and
Magnetic Bodies and on the Great Magnet the Earth’. He suggested that
the Earth itself was a magnet – and he was right. Nowadays, we all
know that our planet has a magnetic field that lines up all the
magnetic compasses. This magnetic field has soaked through all the
life that has evolved on our planet – and may have influenced its
evolution. In 1975, an American team discovered magnets inside
These “magnetic bacteria” actually had a chain of about 20 magnets
lined up inside their tiny bodies. These magnets were about 50
billionths of a metre across – about 1,500 times thinner than a human
hair. These magnets helped the bacteria navigate through their small
ponds. In some cases, when the clumps of magnetic magnetite are big
enough, they can actually twist the bacteria around to line up with
the magnetic field. Since then, other scientists have found tiny magnets of magnetite in marine molluscs, butterflies, sea turtles, salmon, whales, dolphins, honeybees and (you guessed it) even homing pigeons. These magnets can sometimes mess up these animals. For example, in 1976, a Swedish ecologist noticed that migrating birds were getting seriously confused when they flew over a well-known “bulge” in the Earth’s magnetic field.
The birds were being forced to make emergency crash landings at
Norberg, in central Sweden. Norberg sits on top of the largest
magnetic deposit in the world. This lump of iron ore is at least 2 km
deep, about 12 kilometres long and a few kilometres wide. It’s so big
that the Swedes have been able to mine it since the 13th century. This
huge lump of iron ore makes a bump in the Earth’s magnetic field that
is about 60% higher than the normal background magnetic field.
Thomas Alerstam, an ecologist at the University of Lund, noticed that
some migrating birds became disoriented when they flew low over this
body of iron ore. The birds got so confused that they had to land
immediately – but after they pulled themselves together, they could
continue their journey. And in another part of the iron ore deposit,
migrating birds would suddenly plummet 100 metres of altitude as they
flew through sudden changes in the magnetic field.
Around 1976, a series of experiments at Manchester University on third-
year zoology students seemed to prove that humans (or at least third-
year zoology students) had a magnetic sense of direction. The students
were blindfolded and driven over a complex and winding route until
they were between 6 and 52 km away from Manchester University. Each
student was asked to point towards the university twice – first, while
they were still wearing the blindfold, and secondly, after the
blindfold was taken off. To everybody’s surprise, they did much better at finding the university when they were blindfolded – when they were following their instincts, instead of trying to work it out from memory or logic. They seemed to have an innate “sense of direction”.
Then the experiment was repeated with the students all wearing little
bars of metal on their heads. But the little bars of metal were not
all the same – half of them were magnets, while the other half were
non-magnetic brass. The results were impressive – the students wearing
the magnets lost their sense of direction. But the students wearing
the non-magnetic brass could still point to the university. Somehow
the magnets interfered with their sense of direction. So this means
that they their sense of direction was, in some way, magnetic.
In most cases, we reckon that tiny natural magnets inside the
creatures are somehow involved. But now we think there may be another
way to sense microscopic magnetic fields. Sometimes, these magnetic fields can have quite bizarre effects.
An experiment at the University of Western Ontario showed that
magnetic fields can affect a snail’s pace. When these snails (Cepaea
nemoralis ) are placed on a hot surface, they will try to get away
from the heat by lifting up the front of their “foot”. These snails
have the quaint habit of lifting their foot at different speeds,
depending on the time of day – fairly slowly during the daytime, but
very rapidly at midnight. But when the boffins drenched the snails in
a powerful magnetic field, the snails did NOT speed up at midnight.
They lifted their foot at the same speed, no matter what time of day
The scientists also noticed another strange side effect of raising
snails in strong magnetic fields – they died sooner. Magnetic fields have been blamed for killing whales. Back on November 12, 1991, 170 Pilot Whales died when they beached themselves on the west coast of Tasmania. The Earth’s magnetic field is not perfectly smooth, but has highs and lows in it, like hills and valleys. There’s a “magnetic valley” or “magnetic trough” off the coast of Western Tasmania. This magnetic valley runs parallel to the shore for 50 km, and then swings onto the beach at Sandy Cape. By a terrible coincidence, a very strong magnetic storm from the Sun lashed our planet just days before the whales beached themselves at Sandy Cape. Maybe this magnetic storm disrupted the whales’ ability to navigate, and they inadvertently chucked a leftie, and stranded themselves on the beach.
In most cases, when we’ve gone looking, we’ve found magnets in these
creatures that are affected by magnetic fields. But for us, it was as
recently as 1992 that tiny magnets were finally found in the human
brain. A team headed by a geobiologist at Caltech, Joseph Kirschvink,
found crystals of magnetite in the human brain. These crystals are
almost identical to the crystals of magnetite found in bacteria, that
are known to be affected by magnetic fields. These tiny particles of magnetite could make the brain very sensitive to magnetic fields. They could be part of a navigational device that we Oh-So sophisticated humans have forgotten about. It might be very easy to train a strong magnetic sense of direction, so you would never get lost.
But the 1976 experiments on zoology students from Manchester
University might be wrong, and we might not have a magnetic sense at
all. These tiny magnets might be just a way of storing extra iron,
which you need to make red blood cells. Or perhaps these magnetic lumps of iron ore might be part of a natural repair system. They could help brain cells get rid of hydrogen peroxide. Hydrogen peroxide is a natural toxic by-product of oxygen metabolism, and it’s broken down by iron.
But in mid-2000, a team led by James C. Weaver from the Harvard-MIT
Division of Health Sciences and Technology at the Massachusetts
Institute of Technology came up with a completely different way to
sense magnetic fields – a way that did NOT involve tiny magnets. Now
we already know that practically all chemical reactions speed up or
slow down as you change the temperature. But some chemical reactions
are sensitive to external magnetic fields. On one hand, you could
have an exquisitely-sensitive chemically-based “biological compass”.
And, on the other hand, this sensitivity to magnetic fields could
explain some medical effects of magnetic fields upon humans.
James C. Weaver
email : jcw [at] mit [dot] edu
Biological sensing of small field differences by magnetically
sensitive chemical reactions
Weaver JC, Vaughan TE, Astumian RD
Nature 405: 707-709, 8 June 2000
“There is evidence that animals can detect small changes in the
Earth’s magnetic field by two distinct mechanisms, one using the
mineral magnetite as the primary sensor and one using magnetically
sensitive chemical reactions. Magnetite responds by physically
twisting, or even reorienting the whole organism in the case of some
bacteria, but the magnetic dipoles of individual molecules are too
small to respond in the same way. Here we assess whether reactions
whose rates are affected by the orientation of reactants in magnetic
fields could form the basis of a biological compass. We use a general
model, incorporating biological components and design criteria, to
calculate realistic constraints for such a compass. This model
compares a chemical signal produced owing to magnetic field effects
with stochastic noise and with changes due to physiological
temperature variation. Our analysis shows that a chemically based
biological compass is feasible with its size, for any given detection
limit, being dependent on the magnetic sensitivity of the rate
constant of the chemical reaction.”
Subject: FAQs and Misunderstandings
From: sabine [dot] begall [at] gmail [dot] com, hynek [dot] burda [at] uni-due [dot] de
Hello! Sorry for the late reply. It took some time to compose the
FAQs. We’re very grateful that you help us posting these.
Sabine and Hynek
Clarifying some misunderstandings in our cattle and deer magnetic
We never expected such a resonance to our recent PNAS-article and are
completely overwhelmed. Prof. Burda and I give interviews and answer
almost non-stop emails since several days, and we are very exhausted
by now. Therefore, we thought it might be good to post FAQs and
clarify some misunderstandings. Obviously, some reports by the media
lacked important details.
Misunderstanding #1: Cattle (always) point to North.
We never said that cows were pointing north, but that they tend to
align their body axes in roughly a north-south direction (i.e. N-S is
overrepresented, E-W is underrepresented). We neither said that ALL
cows are N-S oriented. I guessed that about 60-70% of the cows in our
data set are oriented appr. N-S (+-30º), but if you analyze big data
sets you obtain the highly significant deviations from a random
Analogon: Note that one of the consequences and expressions of the
Coriolis force is the fact that westwinds prevail in the Northern
hemisphere. The fact that at a given location or at a given time the
wind blows from the South does not mean that the Coriolis force does
Misunderstanding #2: The authors did not account for herding
We also kept herding in mind and in order to obtain statistically
independent data, we took only one mean value per herd into account.
Misunderstanding #3: The authors should interpret their data with
respect to sun. Cows might avoid dazzling, or gain heat by standing
perpendicular to the sun.
Of course, we considered the sun as a factor influencing cattle
alignment. If cows were oriented with respect to the sun, they should
change their position accordingly during the day. This was not the
case. We plotted data relative to the sun (as indicated by shadow
directions), which resulted in a random distribution. We found no
correlation between the direction of shades and body orientation of
The same was true for the deer data (here we could use the time at
which the data had been collected). We observed deer also during
nights (by means of night vision apparatus) and on cloudy days.
Misunderstanding #4: The authors claim that the magnetic sense is more
important than wind.
This is not true. We discussed the factor wind in detail in our paper:
“…cattle orient parallel with strong winds during winter, which
minimizes the area exposed to convective heat loss associated with
It seemed very unlikely that there were windy conditions on all
pastures that we found at different localities all over the world by
using Google Earth.
“…The wind factor can be excluded also for alignment of resting
deer, because deer search for wind-protected places deep in the
forests to rest (and even if it is windy, the wind in the forest is
dampened and changes its direction locally and unpredictably)…”
Note that according to the definition: “Magnetic alignment is a
spontaneous behavioural expression of magnetoreception that appears
particularly in resting animals when body orientation is not
controlled by other factors” (Wiltschko and Wiltschko 2000).
Q: How did you select the coordinates and which image to use?
A: We were simply looking for pastures at Google Earth (without any
given coordinates). It’s quite time-consuming, but once you get the
impression that you found something, it’s hard to stop. We had a list
of requirements (localities in the flat country, no animals near water
or feeding places…). That was the only “guidance”.
Q: Could you explain how your team selected the images used from
Google Earth and how the Czech locations were picked? Your paper says
they were randomly selected but I’m not clear how this random
A: Deer study: Strongly taken, the choice is not truly random – you
see that most localities are in the SW Bohemia (Czech Rep. = Bohemia +
Moravia) and south of Prague. This is given by the fact that our
colleagues and coauthors Jaroslav CERVENY and Oldrich VOJTECH (and me
too) are well acquainted with the Sumava National Park (SW Bohemia)
(where also red deer and roe deer are common; red deer occur in the
Czech Rep. only in mountains on the borders), Oldrich is a wildlife
biologist affiliated with the NP Sumava and Jaroslav, although
officially living in Prague, carries out most of his research projects
in the Sumava Mountains – so they are familiar with the situation,
they know where to find deer etc., they have in the Sumava Mts. their
real or virtual “home on the range, where the buffalo roam and where
the deer and the antelope play” – so it is not surprising that most
observations come from here (otherwise it would surely be not so easy
to record and analyze hundreds of deer beds and observe hundreds of
grazing deer within about four months. And other points on the map
just illustrate the way Jaroslav was taking from Prague to the Sumava
Mountains or from Prague to places of other projects, agencies,
colleague, conferences (in Ceske Budejovice or Brno) etc. In winter
near the roads large herds of roe deer can be observed. No wonder that
Jaroslav in that time needed 4 hours to cover 100 km on good fast
roads… However, there were no other criteria – and all the grazing
or resting (not standing or walking or running ) deer spotted were
measured as to their body orientation. In this respect the choice was
really accidental and random.
Cattle study: We were simply looking for pastures at Google Earth
(without any given coordinates or so). Sometimes you find several
pastures within minutes, and at other times you search and search and
search without finding anything useful. We made a list of requirements
(images with relatively good resolution, localities in the flat
country, no animals near water or feeding places… see the method
section for all details). This was the only “guidance” for our search,
i.e. we did not make a preselection if cattle were EW-oriented. Of
course, the whole search was quite time-consuming.
Q: What caused you to begin this investigation? Why did you decide to
pursue this line of research?
A: The idea for this study is rooted in our work on magnetoreception
in African mole-rats. In the late 1980’s, this subterranean rodent was
the first mammal species for which a magnetic sense could be proven
(this work has been performed by the senior author of the PNAS-paper –
Prof. Hynek Burda). Since then we were interested in the mechanism and
a couple of papers followed. At one point last year the question came
up whether large animals could also sense the Earth’s magnetic field
or not. But of course, it is difficult (or maybe impossible?) to do
these studies in the lab. We wanted to study some kind of spontaneous
behavior because learning experiments can sometimes become very
frustrating. Our first idea was to study sleeping directions of humans
(e.g. when doing camping), but there are too many constraints. So, the
idea arose to look for other large mammals like cattle, and Hynek
Burda was fascinated when he recognized that cattle could be found on
Google Earth satellite images.
Q: Google Earth images are a reliable resource for research?
A: Yes, why not? The images “freeze” a certain situation – it is then
just the question of the sample size and statistics procedures to find
out whether the collected “frozen” situations have a random character
or not. Principally, this is what ethologists call scan sampling (see
). The images are objective and everybody can prove them and will get
the same results.
Q: Would this type of study been possible without Google Earth by just
using field data? How much easier did Google Earth make things?
A: Interesting question! Surely it would be possible but not on the
global scale and with that sample size. (We have also records on many
cattle herds which we observed directly.) One possibility would be to
do it by means of questionnaires sent to interested co-operators
across the globe – but again it would not be so easy. Our Google Earth
method is faster, more objective, allows comparability. It was quite
time-consuming to search for pastures with an adequate resolution in
Google Earth. Sometimes you find a couple of herds within several
minutes, sometimes you search and search and search and do not find
anything. However, Google Earth is perfect for this kind of research,
because the animals are undisturbed by the observer. But there are
also some disadvantages: In most cases it is not possible to
distinguish head and read, so we could analyze axial data only (not
head directions). Also you do not have direct accompanying information
(date, day time, temperature, wind direction).
Q: You indicate that while deer mostly faced north, as many as one-
third faced south, perhaps for protection from predators. Did you
observe anything similar in cattle?
A: Nope, cf.1 – analysis of head direction in the cattle was not
possible or was not performed.
Q: Why do you think herdsmen have not reported this in the past?
A: Of course, we cannot exclude that they have not noted it – but if
so they have not told it to scholars. There are reports in the
literature and it is also a common wisdom of farmers that cattle align
relative to (strong) winds or to sun (e.g. sun basking or shading) –
but there is apparently no written report or recorded common wisdom
regarding alignment when winds and sun do not play a role.
Q: Is there a map you could send (or a Web link to a map) that shows
the layout of Earth’s magnetic field as we understand it, so I can
better understand your results?
A: You can find interesting data and good maps about the Earth’s
magnetic field on the wikipedia website: http://en.wikipedia.org/wiki/Earth_magnetic_field
To understand “magnetic declination”, please read:
For the cattle study we used the fact that some localities have high
values in magnetic declination (i.e. the difference between magnetic
North and geographic North). Depending on whether magnetic North is
located west or east of geographic North the values are positive or
negative. For example the declination is positive at the west coast of
the USA, at the East coast it is negative. So, we just had to search
for pastures on Google Earth at these localities to find that cows
orient on average significantly different at localities with high
positive and negative declination values (and that it is magnetic
North that better predicts their alignment behavior than geographic
Q: Can one of you tell me whether your research – or any other work
that you know about – suggests that cattle in barns would like to
align themselves north-south if possible?
A: Yes, we suggest that cattle would like to align in barns north-
south if possible. However, one problem may be that the magnetic field
in barns is disturbed (this can be expected due to metal in the
construction, electric and water installations (metal tubes), milking
machines etc.) The second problem may be the overcrowding – do the
cows have the possibility to align? Also it can be that cattle would
like to align primarily so that they can observe the door where the
farmer comes, the food source etc. So that they may actually adapt to
the given architecture.
We have no observations and do not know any study which would have
examined this aspect, but we would like to know.
To summarize: Based on the results of our study we suggest that cattle
would like to align N-S in barns in the same way as they do it under
open sky. We suggest also that barns should be situated and
constructed so, that the cattle is being given this opportunity.
However, if someone finds that this is not the case, then still it
does not falsify our hypothesis – it should be tested whether, the
magnetic field inside the barn is not disturbed, and secondly, whether
there are not some other aspects – given by the architecture – which
are for cows more important.
Q: For the average reader, why is it important to know these things?
A: If we assume that our findings are real (i.e. that cattle show this
spontaneous alignment behavior), we could ask what consequences does
the housing in E-W orientation have (i.e. animals kept in barns). Does
it influence the animals’ physiology (e.g. milk production). Of
course, this challenges neurobiological research to find out, why and
how – on the proximate (physiological) level – do these animals align
to the magnetic field. Since these animals have larger brains than
rodents, some new possibilities for research on magnetoreception are
given. Of course the question arises whether humans would also show
such a spontaneous behaviour (e.g. when sleeping) and which
consequences has it for their health?
At least in the Bohemian Forest (Sumava Mts, SW of the Czech rep.) it
was a common practice until about 60 years ago, that when small
farmers built a new stable they first left first their cow lay down on
their plot and then built the stable on the place and so oriented as
the cow lay. Accordingly (at least in old countryside houses, which we
had a possibility to check) the trough was situated on the northern
wall of the stable.