Researchers have explained why cattle will tend to face the same direction when grazing - a behaviour long known to herdsmen and hunters but previously attributed to either prevailing winds or the sun's position.

In fact, Reuters reports, they align their bodies along a north-south axis, suggesting the Earth's magnetic field is the "polarizing factor".

To prove it, Sabine Begall and colleagues at the University of Duisburg-Essen perused 8,510 Google Earth images encompassing 308 pastures and plains worldwide, plus "deer bed" impressions in snow created by around 3,000 deer in over 225 locations in the Czech Republic.

The team found that "whether grazing or resting, these animals face either magnetic north or south". Since the direction of the wind and sun "varied widely where the images were taken", it's reasonable to suggest they're reacting to the planet's magnetic influence.

Begall and colleagues reported in the Proceedings of the National Academy of Sciences: "Our results call for an in-depth study of this phenomenon and challenge neuroscientists, biochemists and physicists to study the proximate mechanisms and biological significance of magnetic alignment."

As Reuters notes, "birds, turtles and salmon are known to use the Earth's magnetic field to guide their migrations, while rodents and one bat species have been found to possess an internal magnetic compass". This is the first time, however, that large mammals have shown this kind of animal magnetism.

The team's report does, though, suggest that humans and whales are "suspected of having an innate magnetic compass", demonstrated by previous research showing that people who "sleep in an east-west position have far shorter rapid eye movement or REM sleep cycles... compared with north-south sleepers who got more REM sleep". ®

Bootnote

In the interests of good science, this hack popped out to have a shufti at a herd of around 20 local cows who were grazing away like good 'uns. Sadly, they mostly appeared to have adopted an east-westish stance - ominously with their noses pointed towards CERN's Large Hadron Collider. Bovine positional anomaly or portent of imminent magnetic field apocalypse? You decide.

Related stories

• Scientists spot pulsar with 4 magnetic poles (10 January 2007)
• Plasma whirlpools breach Earth's magnetic shield (7 December 2006)