Research letter from:... Germany's Magnetic Heartland

cow

(September 22nd 2008) Historically, iron and steel have been the materials upon which Germany's industrial success was built. Much of its metal still comes from the Ruhr cities of Duisburg and Essen where, less famously, lies the University of Duisburg-Essen. The local influence of molten iron seems to have produced a tendency to see the world in decidedly magnetic terms - especially when considering innocently grazing cows and deer. By our corresponding author, Friedrich Eisenfrei

Dr Sabine Begall, a behavioural ecologist from the university, has recently published an analysis of "Magnetic alignment in grazing and resting cattle and deer" in PNAS (2008;105:13451-55). Here she claims that, contrary to the impression that animals roam fields and forests at random, cows, and deer from the Czech Republic, spend most of their time standing in neat alignment along the Earth's magnetic North-South axis.

Previously, Dr Begall worked on subterranean rodents, looking at every aspect of their lives; from how they eat carrots to their "burrow acoustics". She noticed that these small mammals may also use magnetic compasses when underground.

Although a capacity for magnetic compass orientation has also been suggested for larger mammals, including humans (and not simply those equipped for hiking trips), sadly, "the investigation of magnetic orientation in large mammals under reproducible controlled laboratory conditions involving sufficently large sample sizes is difficult."

Nevertheless, with a stroke of experimental improvisation clearly aimed at the taste for high technology among PNAS reviewers, Dr Begall has now found a solution that is quick, cheap and internet-friendly: Google Earth. Yes, it is now possible to download and analyse satellite images taken from several hundred kilometres above the Earth's surface. Sifting through thousands of these Google Earth photographs, Dr Begall reports that she has successfully "determined the axial directions of 8,510 cattle from 308 randomly selected localities (pastures) from six continents."

And the answer is: they're aligned North-South! That is, the body axes of cattle showed a preference for a "rough North-South direction". Although, in her press release Dr Begall says that, "in Africa and South America, the cattle were shifted slightly to a more NE-SW direction," before adding, "but it is known that the Earth's magnetic field is much weaker there." Because, of course, having summarily dismissed the influence of sun and wind, this must be down to magnetism.

Well, you may ask, just how solid is satellite data downloaded over the internet? To control for excessive variability in the images, Dr Begall assures us that, "care was taken to evaluate only pastures in flat country". So, no sloping ground. But remarkably, she then claims to have measured both sexes and diverse races of both dairy and beef cattle despite later admitting to an inconvenient lack of visual resolution. "The resolution of most satellite images did not allow clear and fast distinction between the individuals' head and rear." Just how easy is it to determine the sex of such individual animals? Not that this posed a problem for data collection, since the recordings were "confined to the longitudinal body axis", irrespective of which way the cattles' bottoms were pointed.

By the way, for those of you who have noticed that cows do not walk in exclusively northward-southward directions across the fields, Dr Begall does admit that she removed some anomalies, including, "cattle moving on trails or standing at feeding troughs or watering places, and calves close to suckler cows". Yet elsewhere she says that she could not distinguish between grazing, resting and moving individuals (presumably for that we'll have to wait for Google Earth Video).

So why, apart from magnetism, are these cows aligned along a north-south axis? Could the sun be a determining factor? No, because, "most Google Earth views were apparently made on cloudless, sunny days, judging from short shades, mainly around midday." Yet only 103 of the 308 localities displayed a clear enough shadow to allow her to determine the sun's direction in the photographs. Furthermore, although she claims that, "no images that would suggest sun basking were found," for the parallel analysis of Czech deer (see below), "animals that were obviously sun-basking were not taken into account." Obviously? And why not? Because they're not neatly aligned?

Similarly, observers have noted that cattle often turn their bottoms to the wind, since they don't appreciate it blowing onto their damp nostrils. At certain times of the year, for example during the Northern spring, winds often blow from the south. However, the wind factor is also swiftly dismissed, as Dr Begall reckons that, "in the Northern hemisphere westerlies and in the Southern hemisphere, south eastern trades, are prevailing". And besides, everyone knows that, "generally, airflow is deflected by the Coriolis effect and tends to flow more east-west than north-south." Although she has absolutely no idea what the wind was doing in any of her Google Earth photos, Begall reasons that if the wind were a factor we would have "to presume that winds were strong and blowing mainly from northern or southern directions."

To counter any further suggestion that there are failings in the satellite data, Dr Begall and her co-authors have also made some direct "field observations" of north-south aligned animals, but instead of looking at cows in pastureland away from the blast furnaces and steel mills of Duisburg-Essen, they've chosen to look at wild deer in the Czech Republic.

Here, the north-south body position of 2,974 red and roe deer in 277 locations were recorded by an observer "+/-5° with a compass." And, since "the animals did not notice the observer, or, being habituated, did not apparently react to him," we can't say that he in any way influenced their geometrical distribution. Instead, we are told that only "resting or grazing, i.e. undisturbed, animals were analyzed". Except, of course, those that "were obviously sun-basking" (presumably because the sun is too obviously a determining factor for these uncounted resting individuals) or standing (don't deer stand to graze?), or moving (not easy to get a compass bearing on a moving target - although isn't there a certain mobility to grazing deer?). Well, at least with the deer, they could tell which end was the head and which the tail since it was observed that two-thirds faced northwards, and one-third south.

Yet, when examining the methods, we find that half the alignments are actually based on "measuring beds of animals that had rested in the snow" overnight. It emerges that all the deer data was collected during winter! Now, might cold temperatures, snow, trees, or mountains play a role in the deers' behaviour? No, because only sun and wind are considered as alternatives to the obvious explanation that thousands of well-aligned cows and deer are responding to magnetism! Especially since what was initially described as a "roughly" North-South axis is then shown to be nicely skewed towards Magnetic North.

Dr Begall assures us that there are several reasons why standing in Magnetic North-South facing rows could be useful: "It has been speculated that maintaining a symmetric position to the field lines somehow influences certain physiological processes." Like what? "Rapid eye movement latency in humans is shorter when sleeping E-W rather than N-S." That's one we can test at home, but does it really apply to grazing cows?

Well, she says, "maintaining a certain magnetic direction may also provide a constant directional reference for spatial orientation, which might be useful, e.g. after disturbance and fast escape". For cows?

Several commentators wondered if Dr Begall was aware that many cows are fed magnets to help prevent 'hardware'. This is not a joke! It seems that from a very early age, cattle the world over are fed small magnets that remain in their stomachs, attracting metallic detritus, like bits of barbed wire, nails and staples that modern cattle carelessly scoff down with their grass. This 'tramp iron' can lodge in the reticulum, causing irritation, inflammation, reduced milk production and weight loss. Hence the cow magnets, which help prevent this 'hardware disease' by attracting stray metal away from the folds and crevices of the rumen and reticulum. One magnet is sufficient to last the entire life of a cow. Now, might this be an orientation factor in grazing cattle? Alas, Google Earth images currently fail to distinguish between cows containing stomach magnets.