Gravity. Electricity. Magnets. These unseen forces have made life on Earth possible, and they continue to affect organisms every day, whether we realize it or not. Case in point: A new study found that foraging wild boars and warthogs align their bodies along a magnetic north-south axis. The research was published in the journal Mammal Review. 

This might sound like some wacky pig-specific phenomenon, but scientists are learning that it’s a relatively common behavior. Animals like lobsters, birds, butterflies, and foxes have all been observed aligning their bodies or homes along invisible magnetic lines. Just a few weeks ago, in early June 2016, researchers in the Czech Republic reported that startled roe deer prefer to flee along a north-south axis, even when that brings them closer to the threat. 

Like the roe deer, the wild boar (Sus scrofa) is abundant in the Czech Republic—sometimes too abundant for human comfort. Exploding boar populations can damage crops, carry disease, and cause car accidents when they wander onto roads. It’s kind of a funny image, but the crashes themselves are no laughing matter; when a moving vehicle hits a 200-pound animal, somebody's going to get hurt or even killed.

So researchers have a lot to gain by understanding why these animals act the way they do. Researchers at the Czech University of Life Sciences (the same place that conducted the roe deer research) designed a new experiment to track the foraging and resting behaviors of 1614 Czech wild boars and 1347 of their African cousins, the warthogs (Phacochoerus africanus). 

Image credit: Jaroslav Cerveny/Czech University of Life Sciences

Observers watched the boars and warthogs with binoculars from a safe distance, noting the orientation of the animals’ bodies. They also examined the shape and arrangement of the animals’ beds in the dirt. 

Sure enough, both European and African pigs preferred to align their bodies and their beds along a north-south axis, angled slightly to the east. No matter the time of day, season, or weather, the boars and warthogs tended to stay true to their internal compasses. 

Pascal Malkemper is senior author of the Mammal Review paper. “The fascinating findings add on to a well-growing body of evidence for a magnetic sense in mammals,” he said in a press statement. “The interesting questions that arise now are how they are able to sense the magnetic field and whether they really use it for navigation.” 

The authors also asked another interesting question: Do boars’ internal compasses have anything to do with the car crashes? Electromagnetic activity has been shown to affect other grazing animals, and roads are typically accompanied by power lines. “It would be interesting to test whether or not [the boars] align themselves randomly when they are in the vicinity of electromagnetic disturbances,” the authors write. “High-voltage power lines often border streets, so there may be a relationship between car accidents involving wild boars and the distance between electromagnetic disturbances and these crash sites.”