He says, “Imagine you had a flashlight attached to your belt that was pointed down at the ground at a fixed angle of say 60 degrees. At that spot, the fox knows that it’s a fixed distance away from its prey, and it knows exactly how far to jump to land upon it. It’s searching for that sweet spot where the angle of the sound hitting its ears matches the slope of the Earth’s magnetic field. As the fox creeps forward, it listens for the sound of a mouse. This targeting system works because the Earth’s magnetic field tilts downward in the northern hemisphere, at an angle of 60-70 degrees below the horizontal. Červený suggests that a red fox could use the Earth’s magnetic field as a “rangefinder”, to estimate the distance to its prey and make a more accurate pounce. “This explanation… has plausibility only because there’s hardly any other mechanism that indicates directions.” Roswitha Wiltschko, one of the pioneers who deciphered the magnetic sense of birds, says, “The findings are really astonishing.” But she also thinks that they’re speculative. John Philips, who studies magnetic senses at Virginia Tech, says “The challenge (and the fun) for anyone interested is to come up with explanation that can explain the data. The strength of the authors’ conclusions are only as good as the inability of anyone else to come up with an alternative hypothesis.” Červený thinks that the only remaining explanation is that foxes align their pounces to the Earth’s magnetic field. He found that the animals leapt in the same direction regardless of the time of day, season of year, cloud cover, or wind direction. In all other directions, only 18% of their pounces were successful.Ĭould the foxes be taking their direction from the environment? Červený thinks not. If they pounced to the north-east, they killed on 73% of their attacks if they jumped in the opposite direction, they success rate stayed at 60%. They were more likely to make a kill if they jumped along their preferred axis, particularly if their prey was hidden by high cover or snow. This fixed heading was important for their success as hunters. They found that foxes strongly prefer to jump in a north-easterly direction, around 20 degrees off from magnetic north. The team recorded almost 600 mousing jumps, performed by 84 foxes at a wide variety of locations and times. Červený spent over two years studying wild red foxes in the Czech Republic, with the help of a 23-strong team of wildlife biologists and experienced hunters. He thinks that they’re using the Earth’s magnetic field to hunt. Jaroslav Červený has found that when red foxes pounce, they mostly jump in a north-easterly direction. This pounce, known as ‘mousing’, is a common sight but there’s more to it than meets the eye. Once it pinpoints the mouse’s location, it leaps into the air to surprise its prey with a strike from above. It creeps forward slowly, listening intently with erect ears. The snow-covered ground masks the sight of its prey but the fox can still hear the telltale rustle of a mouse. It’s winter on a British meadow, and a red fox is on the prowl.
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