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A study published this week in the journal Frontiers in Zoology suggests that dogs choose to relieve themselves along a north-south axis in line with Earth's magnetic field. The Motherboard blog reported on the study's findings, saying that the research was carried out by a team of Czech and German scientists.

"Dogs are sensitive to small variations of the Earth's magnetic field," said the research team. "Dogs preferred to excrete with the body being aligned along the North-south axis" rather than the East-west axis.

The study examined the daily habits of 70 dogs during 1,893 defecations and 5,582 urinations over the course of two years. Consistently, during times of calm electromagnetic "weather," the dogs chose to eliminate while facing north or south.

Dogs are not the only animals that are sensitive to the Earth's magnetism. When it comes time for them to mate, salmon use their sense of the Earth's magnetism to find their way back to the spawning grounds where they were born. Birds, similarly, migrate along magnetic lines. Even ants have been proven to have a sense of the Earth's alignment and to distinguish between north, south, east and west.

As to why the dogs prefer to poop facing north or south rather than east or west, that's still a mystery.

"It is still enigmatic why the dogs do align at all, whether they do it 'consciously' (i.e., whether the magnetic field is sensorial perceived (the dogs 'see,' 'hear' or 'smell' the compass direction or perceive it as a haptic stimulus) or whether its reception is controlled on the vegetative level (they 'feel better/more comfortable or worse/less comfortable' in a certain direction)," wrote researchers, "Our analysis of the raw data (not shown here) indicates that dogs not only prefer N-S direction, but at the same time they also avoid E-W direction."

The dogs did not exhibit the preference, however, when they were being walked on leashes. It was only when left to their own devices that they expressed the preference.

David Ferguson David Ferguson is an editor at Raw Story. He was previously writer and radio producer in Athens, Georgia, hosting two shows for Georgia Public Broadcasting and blogging at Firedoglake.com and elsewhere. He is currently working on a book.