Do cows sense magnetic fields?

25/03/2009

There has been evidence for a while that some birds use the earth's static magnetic field for navigation.  But could larger animals such as cows and deer also sense the magnetic field?

Two scientific papers published in the Proceedings of the National Academy of Sciences of the USA have suggested that they might, and have also implicated power lines.  They use Google Earth photographs to look at the orientation of grazing cows.  The first paper suggests that cows (and deer) naturally orient themselves north-south.  The second paper suggests that this north-south orientation can be disrupted by the presence of a power line.

These are controversial studies - not everyone seems ready to accept them or convinced of the relevance of bird and animal navigation to the EMFs produced by power lines - but they clearly deserve taking seriously.

The studies raise the issue of the relative direction of power-line fields and the earth's magnetic field.  See more information on the direction of magnetic fields from power lines.

Proc Natl Acad Sci U S A. 2008 Sep 9;105(36):13451-5. Erratum in:
Proc Natl Acad Sci U S A. 2008 Nov 4;105(44):17206.
Magnetic alignment in grazing and resting cattle and deer.


Begall S, Cerveny J, Neef J, Vojtech O, Burda H.
Department of General Zoology, Faculty of Biology and Geography, University of Duisburg-Essen, 45141 Essen, Germany.

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.

 

Proc Natl Acad Sci U S A. 2009 Mar 19.
Extremely low-frequency electromagnetic fields disrupt magnetic alignment of ruminants.

Burda H, Begall S, Cerveny J, Neef J, Nemec P.
Department of General Zoology, Faculty of Biology and Geography, University of Duisburg-Essen, 45117 Essen, Germany;

Resting and grazing cattle and deer tend to align their body axes in the geomagnetic North-South direction. The mechanism(s) that underlie this behavior remain unknown. Here, we show that extremely low-frequency magnetic fields (ELFMFs) generated by high-voltage power lines disrupt alignment of the bodies of these animals with the geomagnetic field. Body orientation of cattle and roe deer was random on pastures under or near power lines. Moreover, cattle exposed to various magnetic fields directly beneath or in the vicinity of power lines trending in various magnetic directions exhibited distinct patterns of alignment. The disturbing effect of the ELFMFs on body alignment diminished with the distance from conductors. These findings constitute evidence for magnetic sensation in large mammals as well as evidence of an overt behavioral reaction to weak ELFMFs in vertebrates. The demonstrated reaction to weak ELFMFs implies effects at the cellular and molecular levels.