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Heading north
By Michael Banks
Do cows align their bodies along the Earth’s magnetic field lines when grazing? What at first seems like a simple enough question is in fact becoming a hotly contested area of research.
In 2008 the answer was “yes” as zoologist Sabine Begall from the University of Duisburg-Essen in Germany and colleagues used images from Google Earth to study the patterns of 8500 cattle from 208 pastures around the world.
They found that regardless of where the cows came from, they aligned their bodies along the North–South of the Earth’s magnetic field. The effect was most obvious at high latitudes, they concluded, where the difference between magnetic North and geographical North are greatest (PNAS 105 13451).
There was a small snag, however, as the resolution of the images meant it was not clear whether it was the heads or tails of the animals that were pointing north – no doubt giving Begall and colleagues a case for further studies.
However, magnetoreception in cows has now been disputed by Jiri Hert from Charles University in the Czech Republic and colleagues who say there is no evidence for such alignment in their Europe-wide study of some 3412 individual cows in 322 herds (arXiv:1101.5263).
They claim that Begall and colleagues selected the herds and individual animals in an “inadequate way” and that “possible subconscious bias” could lead to the discrepancy between the studies as well as the use of poor-quality Google satellite images.
However, zoologist Hynek Burda from the University of Duisburg-Essen in Germany who was involved in the Begall study says it would be “useful” to see the images that Hert and colleagues have evaluated. “The images we have assessed were not of poor quality and there was no problem in determining the body axis [of the cows],” says Burda, who adds that their analysis has been supported at a forum held at the Royal Institute of Navigation.
“The case cannot be closed if only two studies come to different results,” Hert told physicsworld.com. “We hope that our study will provoke other scientists to repeat the analysis of the magnetic behaviour of cows and other mammals.”
Hert adds that he will not be studying the topic any further, however, but that his work will be “oriented in other directions” from now on.
I think any bias might be more satellite image related than on the part of Sabine Begall. To obtain a satellite picture of the surface of the earth in the visible wavelengths requires two conditions an absence of cloud cover and sunlight, that may provide the image bias.
Cows most likely prefer the sun shining on their backs and not in their eyes. These two goals can be met in the Northern Hemisphere by turning to face the North. This would mean that, by default, the cows appear to be aligning themselves with the direction of the magnetic field. If further scientific effort is really required then satellite images from herds in the Southern Hemisphere should selectively be examined.
Ron Neale
Ron@neales.demon.co.uk
@Ron, Cows are like many herbivores in that their eyes are on the side of their heads so they can see their flanks. This means that in a North-South alignment, they would still have the sun in one of their eyes. Your reasoning left out this fact.
After my first post above I have received by private communication some comments from Sabine Begall, as follows:
“”We have considered also the position of the sun (as indicated by the direction of the shadows) and found no correlation between body position of cattle and position of the sun (cf., Begall et al. 2008). Furthermore, in our second study where we looked on cows under high-voltage power lines (extremely-low frequency magnetic fields) body alignment of cattle was randomized, and with further distance from the power lines cattle become more and more aligned. This result would not be expected if cattle align themselves with respect to the sun.””
I hope that sets the record straight.
We have also discussed my suggestion of the possibility that blood or ions (conductors) flowing along the length of the cow’s body when it is at a rt angle to the earths magnetic field may cause some form of discomfort. This causes the cows to align themselves parallel to the earth’s magnetic field to relieve that discomfort. Sabine said she had received a similar sugestion from another source.