Proc. Natl Acad. Sci. USA doi: 10.1073/pnas.0811194106 (2009)

Having previously shown statistically that cows and deer preferentially align their bodies north–south, Hynek Burda of the University of Duisburg-Essen in Germany and his colleagues now provide more evidence for these animals' magnetic sensing.

If this alignment is truly due to some sensing of the magnetic field, strong, nearby magnetic fields such as those from power lines should disrupt ruminant orientation.

Using satellite and aerial photographs, the researchers show that 1,699 cows grazing within 50 metres of overhead power lines at various European locations were randomly oriented. Field observations of 653 deer within 50 metres of power lines in the Czech Republic also revealed random orientation.