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Environment & Science

Uncovering the mystery of an animal's inner compass

This picture taken on August 7, 2012 shows pedigree Burmese cats in their enclosure at the 'Inthar Heritage House' located on the shores of Inle Lake in eastern Shan State.
This picture taken on August 7, 2012 shows pedigree Burmese cats in their enclosure at the 'Inthar Heritage House' located on the shores of Inle Lake in eastern Shan State.

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You've likely heard of the concept of animal magnetism. Well, turns out scientists think some animals can actually have internal compasses that detect the earth's magnetic field. They think this may explain how some migrating animals are able to navigate long distances with pinpoint accuracy. 

One case in particular inspired science writer and KPCC contributor Veronique Greenwood to look into this phenomenon

In January, Holly the cat baffled scientists when she was found exhausted and hungry after traveling 200 miles back to her home in West Palm Beach, Florida. The cat's owners had lost her months earlier during a trip to Daytona Beach, but that cat came home in bad shape, its claws swollen and worn down. 

Cases like this are extremely rare, so scientists have not been able to explain how the cat managed to find its way home. 

"The truth is we really don't know how cats do that kind of trick, there's not a lot of documented events like this, this seems to be pretty unusual," said Greenwood. "When something's not repeatable, it's a little hard to figure out scientifically what's going on, so if you ask scientists what they think about how this cat found her way home, and the answer is, 'We have no idea.'"

While we may not know how a cat could pull off this feat of navigation, scientists do know how a large number of other species manage to find their way home. One way animals navigate is similar to that of the sailors of yore: By following the stars. 

"Dung beetles can manage to roll their precious balls of dung in a straight line as long as the Milky Way is in view," said Greenwood. "If the Milky Way is not in view, they start to wiggle around and they can't go in a straight line anymore. That's bad for a dung beetle because if they wind up back at the ball pile, they might get their ball stolen by another beetle."

There is also evidence that some animals can sense the earth's magnetic fields. Homing pigeons, for example, have been known to use the earth's magnetic field to find their way home. In a study by William Keeton in 1971, homing pigeons were found to have difficulty flying home when magnets were applied to their backs.  Mice, mole rats and bats have also been shown to use magnetic cues for navigation. 

"There are plenty of things that we can't see that animals can," said Greenwood. "For one thing, there's ample evidence that animals can sense the earth's magnetic field, which is what our compasses respond to, we need a compass to see it and many different kinds of, especially migrating animals have it somewhere within them. 

In addition, scent had also been shown to be a powerful tool used by animals for navigation. 

"We know that there's some element of scent involved in animal navigation, for instance we know that there are salmon that as they are getting close to their home river, can actually smell their river when they're out in the ocean," said Greenwood. "We know that sharks can sense these really really faint electric currents, the idea is maybe they use then to track prey, but we're not really sure."

For now, just how a common house cat could find its way home 200 miles away will remain a mystery.