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Which way does a pig point? The answer, it turns out, is north – or south.

Many organisms ranging from birds and bees to bacteria are known to have a magnetic sense that helps them navigate. But now it seems swine sense Earth’s magnetic field too – a finding that could help us win the fight against out-of-control feral pigs.

at the University of Duisburg-Essen, Germany, and his colleagues made this discovery by observing more than 1600 wild boar in the Czech Republic, and more than 1300 warthogs in six African nations. Estimating the direction each animal was pointing in, the biologists found that, on average, they lined up closely with the north-south axis.

And it’s not just how they stand – they also found that wild boar beds face north or south, with a ridge at one end for it to rest its head. Altogether, the team suggests this shows these swine species have a strong sense of Earth’s magnetic fields.

“The fact that the animals align with the field lines suggests that they have a magnetic compass which they might use to navigate,” says Malkemper. Wild pigs can migrate over 50 kilometres between grazing areas. Perhaps a magnetic map of the landscape helps them find their way, he says.

Magnetic warfare

This could be a valuable finding. Feral pigs – which are descended from escaped farm animals – are a damaging invasive species around the world, causing at least $1.5 billion a year in damage in the US alone, through destruction of crops, traffic accidents and disease transmission.

“This is a global situation with wild pigs,” says of the Savannah River National Laboratory in South Carolina. “If it’s got a calorie in it, and they can get their mouth around it, they’ll eat it.”

But it may be possible to use electric fields to disrupt feral pigs’ movements by confusing their compass, says of the Virginia Polytechnic Institute and State University in Blacksburg. The idea holds some weight: high-voltage power lines have been found to cause herds of cattle and deer .

It may be possible to baffle pigs’ sense of direction in the same way.  “Tapping into that and disrupting it certainly could cause issues within a population,” says Painter.

Mayer is interested to know if placing power lines across migration routes could control the movement of these pigs. “Does it create a source of confusion? Is it a barrier at all? I think that would definitely be something worth doing,” he says.

Journal reference: Mammal Review,

Read more: Human versus pig: Can we outwit the hog hordes?