Animal Magnetism: The Science Of Internal Compasses In Everything From Pooping Dogs To Bluefin Tuna

The year in science news started off with a delightfully loopy story: the discovery by a group of scientists that dogs seem to prefer to poop with at least one of their ends pointing towards magnetic north. A German-Czech team of scientists reached this conclusion after two years observing thousands of individual doggy-dump sessions.

This is hardly the first time that this group of researchers has stumbled upon a curious case of animal magnetism. Blind, naked mole rats supplement their sense of smell with magnetic sensing to navigate underground tunnels. Bluefin tuna take fast, deep dives at dawn and dusk, when magnetic interference from the sun is lowest, possibly as a way to fine tune their magnetic-based navigation. From turtles to birds, there’s a surprising number of creatures that carry their own internal compasses.

“As for people, there have been studies which suggest that magnetic fields influence biological processes such as rapid eye movement in sleep,” the Economist noted in 2008. “Also, electroencephalograms seem to vary according to the direction in which people are facing when they are recorded.”

But attempts to unravel the mysteries of animal magnetism has caused its fair share of scientific scraps.

The same team that published the dog-pooping research included scientists that in 2008 found that cattle seem to prefer standing with their bodies in alignment to Earth’s magnetic field. Senior researcher and University of Duisburg-Essen researcher Hynek Burda and colleagues reached this conclusion by looking for cows in Google Earth’s satellite pictures. They also did a follow-up study showing that this phenomenon was absent when the cattle were standing near electric power lines – which could plausibly disrupt any magnetic sensing ability.

But not everyone was convinced.

In 2011 another group of researchers, led by Czech Technical University researcher Lukas Jelinek, said they couldn’t re-create Burda’s findings with a different set of Google Earth images. Burda’s team, in turn, says the replication attempt didn’t account for factors like proximity to power lines or sloping landscapes. Some of the rival team’s images also appeared to contain hay bales and sheep, not cows.

“One half of their data is just noise,” Burda told Nature.

When Burda’s reanalyzed the data from Jelinek, they found the same original pattern – in general, cows prefer to stand along geomagnetic lines.

Just how animals can sense magnetic fields and relay that information to the brain is still something of a mystery. Take pigeons, for example – one of the classic examples of animals that are thought to use magnetism for navigation. For a long while, researchers thought that pigeons had iron-rich nerve cells in their beaks. But a 2012 study from University College London researcher Mark Lythgoe and colleagues found iron in pigeon beaks was mostly inside the white blood cells -- and it wasn’t even magnetized iron, so there’s virtually no way it could have been used to sense magnetic fields or transmit the information to the brain.

Lythgoe and colleagues argued that their findings called for a reevaluation of the behavioral studies that form the foundation of the magnetic navigation theory. Other pigeon experts, feathers ruffled, said that perhaps the team simply couldn’t find the right iron-containing structures in the beak, while others suggested that the pigeon’s compass may actually lie in the eyes.

Meanwhile, most of us will have to get by with Google Maps.