Foxes Use The Earth’s Magnetic Field To Hunt

By Nolan Moore on Wednesday, May 14, 2014
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“Fuzzy animals by day. Food robbers by night.” —Fantastic Mr. Fox (2009)

In A Nutshell

Quite a few animals are in tune with the magnetic field. Sharks, turtles, ants, and even cows can sense the Earth’s magnetic poles. And now Czech researcher Jaroslave Cerveny thinks foxes use the magnetic field to hunt mice that are hiding in the snow.

The Whole Bushel

Unless your name happens to be Boggis, Bunce, or Bean, chances are good you love foxes. They’re cute, intelligent, and sound like George Clooney. They also have superpowers, sort of. Foxes are excellent hunters and spend their days feasting on mice, voles, and shrews. However, things get a bit tricky when winter rolls around. Their prey starts burrowing down into the snow, making it difficult for foxes to catch their dinner. So since foxes can’t sneak up on their prey, they resort to a tactic called “mousing.” This involves leaping through the air, breaking through the snow, and snagging those tasty mice before they run away. It’s amazing to watch, but it poses an interesting question. If the rodents are under the snow, how does the fox know where to jump?

Czech scientist Jaroslave Cerveny wondered the same thing. Determined to find the answer, he gathered a team and spent a lot of time watching foxes hunt. By the time the study was over, the group had recorded 84 foxes jumping nearly 600 times. They also came up with some pretty interesting statistics. Whenever the foxes jumped in a northeasterly direction (20 degrees off magnetic north), they had a 73 percent kill rate. Whenever they pounced to the southwest, the opposite direction, there was a 60 percent chance they’d snap up their supper. However, if they sprang in any other direction, they only caught their prey a measly 18% of the time. What was going on?

Cerveny didn’t think foxes were getting cues from their surroundings since their success rates were consistent despite the water, season or time of day. Instead, the scientist believes foxes have the ability to sense the Earth’s magnetic field. Coupled with its excellent hearing ability, this sixth sense works as a tracking device, helping the fox hone in on its prey. Now, while the Czech researcher isn’t exactly sure how this mechanism works, he has a solid theory. Cerveny posits that when a fox hears something scurrying under the snow, it listens to the mouse’s footsteps. At the same time, it’s focusing on the downward slope of the magnetic field in the Northern Hemisphere. When the fox hears the mouse reach that slope (or when its sights align, if you will), it then can estimate the distance between itself and its snack. That’s when the fox springs through the air, using its tail to direct its flight path, and lands on top of the runaway rodent. Of course, if it misses, it can always buy a bandit hat and raid the local chicken farm.

Show Me The Proof

NPR: ‘You’re Invisible, But I’ll Eat You Anyway.’ Secrets Of Snow-Diving Foxes
Discover: Foxes use the Earth’s magnetic field as a targeting system