Dogs are known for their world-class noses, but a new study suggests they may have an additional, albeit hidden, sensory talent: a magnetic compass. The sense seems to allow them to use Earth's magnetic field to calculate shortcuts in unknown terrain.
The finding is the first in dogs, says Catherine Lohmann, a biologist at the University of North Carolina, Chapel Hill, who studies "magnetoreception" and turtle navigation. She notes that the navigation skills of dogs have been much less studied compared to migratory animals such as birds. "That'It's an idea of how [dogs] build your image of space, "adds Richard Holland, a biologist at Bangor University who studies bird navigation.
There were already indications that dogs, like many animals, and perhaps even humans, can sense Earth's magnetic field. In 2013 Hynek Burda, a sensory ecologist at the Czech University of Life Sciences in Prague who has worked in magnetic reception for 3 decades, and his colleagues showed that dogs tend to orient themselves from north to south while urinating or defecating. Because this behavior is involved in marking and recognizing territory, Burda reasoned that the alignment helps dogs determine location relative to other points. But stationary alignment is not the same as navigation.
In the new study, Burda's graduate student Kateřina Benediktová initially placed video cameras and GPS trackers on four dogs and took them on a hike into the forest. Dogs would run to chase the smell of an animal for 400 meters on average. The GPS tracks showed two types of behavior during their trips back to their owner (see map below). In one, called tracking, a dog would return to its original route, presumably following the same scent. In the other behavior, called exploration, the dog would return along an entirely new route, jerking without backing down.
When Benediktová showed the data to Burda, his Ph.D. Counselor, he noticed a curious feature: In the middle of a scouting race, the dog stopped and ran about 20 meters along a north-south axis (see video, below) before beginning to navigate backwards. Those short runs seemed like an alignment across the magnetic field, but Benediktová didn't have enough data to be sure.
So Benediktová and Burda expanded the project, releasing 27 dogs on several hundred trips over 3 years. Colleagues in the game management and wildlife biology department, where almost everyone has a hunting dog, collaborated.
The researchers looked closely at 223 scouting races, in which the dogs traveled an average of 1.1 kilometers on their return. In 170 of these trips, the dogs stopped before returning and running about 20 meters along a north-south axis. When the animals did this, they tended to return to the owner by a more direct route than when they did not, the authors report in elife. "I am really very impressed with the data," says Lohmann.
During walks in the forest, the team tried to avoid giving the dog other navigational cues. Whenever possible, a dog was taken to a part of a forest he had never been to, so he could not rely on familiar landmarks. A dog was also unable to navigate backward looking for its owner, who hid after the dog left to wander. The smell didn't seem to play a role either, because the wind rarely blew from the owner to the dog when he returned.
Burda believes that dogs run along a north-south axis to find out which direction they are in. "It is the most plausible explanation," she says. The implication, Lohmann says, is that dogs can recall their previous course and use the reference to the magnetic compass to discover the most direct route home. "I am intrigued," she says.
Adam Miklósi, who specializes in canine behavior at Eötvös Loránd University, says that designing magnetoreception experiments is complicated because it is difficult to make an animal rely on it alone. "The problem is that to 100% test the magnetic sense, or any sense, you have to exclude all the others."
Burda and Benediktová are taking a different approach. In a new experiment, they will place magnets on the dogs' collars to disturb the local magnetic field and see if this hinders their ability to navigate. The idea dates back to a controversial experiment published in 1980 in Science, in which the magnets caught in the blindfolds seemed to alter an intuitive sense of magnetic reference in humans in humans.
Miklósi says that it would not be surprising to discover that dogs can use the magnetic field to navigate, it seems to be an ancient ability, and it could be present in any mammal that traverses large territories. Lohmann agrees. "Hopefully this is something that many animals can do to get home after hunting," he says, "and it's great to see it on a dog."
