Canine Compass?

Zelda, a shepherd mix, went missing last February just 10 days after being adopted by a family in Chanhassen, Minnesota. Volunteers began a search for the dog, posting flyers and following leads on social media. Seneca Krueger joined in. She’d fostered Zelda for seven months before the pup moved in with her new owners. After 97 days, someone spotted Zelda. The dog was just two blocks from her old foster home in St. Paul—48 kilometers (30 miles) away from her new place in Chanhassen.

Everyone agreed that after Zelda’s epic journey to be with her foster mom, the dog should stay with Krueger for good. Zelda isn’t the only canine to have performed such an amazing feat of navigation. Many lost dogs have traveled long distances to reunite with their families. How exactly do the animals find their way home?

Researchers in the Czech Republic suspect that dogs may have a kind of built-in compass. They might use it to orient themselves using Earth’s magnetic field. Studies have found evidence of this phenomenon, called magnetoreception, in other animals with an uncanny sense of direction, such as birds, whales, and turtles. The scientists set up a new experiment to see if dogs are also part of that club.

Last February, a shepherd mix named Zelda went missing. A family in Chanhassen, Minnesota, had adopted her just 10 days earlier. Volunteers began a search for the dog. They posted flyers and followed leads on social media. Seneca Krueger joined in. She’d fostered Zelda for seven months. Then the pup had moved in with her new owners. After 97 days, someone spotted Zelda. The dog was just two blocks from her old foster home in St. Paul. That’s 48 kilometers (30 miles) away from her new place in Chanhassen.

Zelda had made a long journey to be with her foster mom. Everyone agreed that the dog should stay with Krueger for good. Zelda had performed an amazing feat of navigation. And she isn’t the only one. Many lost dogs have traveled long distances to rejoin their families. How do the animals find their way home?

Researchers in the Czech Republic have an idea. Dogs may have a kind of built-in compass. They might use it to orient themselves with Earth’s magnetic field. This ability is called magnetoreception. Studies have found evidence of it in other animals with an amazing sense of direction. They include birds, whales, and turtles. Are dogs also part of that club? The scientists set up a new experiment to find out.

To learn more about dogs’ potential magnetic-sensing abilities, biologist Katerˇina Benediktová of the Czech University of Life Sciences and her co-investigators decided to study hunting breeds. For generations, people have bred dachshunds, fox terriers, Welsh terriers, and other hunting dogs to track prey and then find their way back to their owners. “We know about homing behaviors in these breeds from observations, but they haven’t been studied in detail,” says Benediktová.

To test the dogs’ navigation skills, the scientists attached vests with video cameras and GPS trackers to 27 adult dogs. Then they sent the animals for walks in the woods with their owners. Benediktová even brought some dachshunds of her own to take part in the study. Many of the other participating pooches belonged to colleagues. While out walking, the pups were allowed to run off to chase an animal or follow an interesting scent. Then the owner hid behind a tree or bush near the spot where the dog had taken off until it made its way back.

Katerina Benediktová is a biologist at the Czech University of Life Sciences. She and her team wanted to learn more about dogs’ possible magnetic-sensing abilities. So they decided to study hunting breeds, such as dachshunds, fox terriers, and Welsh terriers. For generations, people have bred hunting dogs to track prey and then find their way back to their owners. “We know about homing behaviors in these breeds from observations, but they haven’t been studied in detail,” says Benediktová.

To test the dogs’ navigation skills, the scientists used vests with video cameras and GPS trackers. They attached them to 27 adult dogs. Then the animals walked in the woods with their owners. Some of Benediktová’s own dachshunds took part in the study. Many other dogs in the study belonged to her colleagues. On their walks, the pups were allowed to run off. They chased an animal or followed an interesting scent. The owners stayed near the spot where the dog had left. They hid behind a tree or bush until the dog came back.

Over a period of three years, the doggie participants completed 622 walks. The researchers analyzed GPS tracking data from the journeys. They found that 59 percent of the time, dogs took the same route going away from their owners and on the way back. In these cases, says Benediktová, the dogs probably followed their own scent trails. On 33 percent of the trips, dogs took a completely different route back— scouting through new territory the entire way. And on 8 percent of the trips, the dogs used a combination, following part of their original path back and also covering some new ground (see Types of Trips).

The scientists focused their study on the scouting trips where the dogs never retraced their steps. They discovered that most of the time, the dogs did something curious just before heading back toward their owners. No matter which direction the animals had been traveling, they stopped and ran for roughly 20 meters (66 feet) along a north-south route aligned with Earth’s geomagnetic axis (see Magnetic Planet). “This very surprising,” says Benediktová. No one had ever documented it before. Further analysis turned up an intriguing connection: Dogs who performed this north-south jaunt took a more direct route back than those who didn’t.

Over a three-year period, the dogs completed 622 walks. The researchers studied GPS tracking data from the walks. Sometimes, dogs took the same path going away from their owners and coming back. That happened 59 percent of the time. On these trips, dogs were probably following their own scent trails, says Benediktová. Dogs took a completely different path back on 33 percent of the trips. They scouted through new territory the entire way. And on 8 percent of the trips, the dogs did both. They followed part of their original path, and they covered some new ground (see Types of Trips).

The scientists focused on the scouting trips, with a different path on the way back. They found that most of the time, the dogs did something odd. Just before heading back toward their owners, the dogs stopped. Then they ran for about 20 meters (66 feet) along a north-south path lined up with Earth’s geomagnetic axis (see Magnetic Planet). They did this no matter which direction they had been going. “This behavior was very surprising,” says Benediktová. No one had ever recorded it before. The team looked closer and found an interesting connection. When dogs performed this north-south run, they took a more direct path back.

Benediktová’s team suspects that dogs orient themselves by tuning in to Earth’s magnetic field. Identifying and moving in a known direction may help them figure out where to go next—just like a person navigating with a compass. And it may help them construct a mental map of the area as they’re deciding how to get back.

Before scientists can determine whether dogs truly sense magnetism, they need to rule out other potential explanations for the animals’ behavior. Benediktová’s team explored whether the dogs could have instead been using visual landmarks to orient themselves north-south. If so, taller dogs with a better view of their surroundings should have had an easier time spotting objects than shorter ones. But that didn’t happen: Tall and short dogs oriented themselves equally well. The researchers also checked whether the dogs were relying on the wind direction or the position and visibility of the sun, but these didn’t explain the results either.

Benediktová’s team suspects that dogs tune in to Earth’s magnetic field. She thinks that’s how they orient themselves north-south. They find and move in a known direction. That may help them figure out where to go next. It’s similar to how a person navigates using a compass. This process may help dogs make a mental map of the area as they decide how to get back.

Scientists want to find out whether dogs truly sense magnetism. But first, they need to rule out other possible reasons for the animals’ behavior. Benediktová’s team considered other explanations. Could the dogs have been using visual landmarks to orient themselves north-south? If so, taller dogs should be better at getting themselves lined up than shorter ones. That’s because they have a better view of their surroundings. But that didn’t happen. Tall and short dogs oriented themselves just as well. Could the dogs be using the wind direction? What about the position of the sun? The scientists checked, but these didn’t explain the results either.

Benediktová is planning a follow-up experiment to investigate further. This time, she’ll look for differences in how dogs navigate with and without a small magnet attached to each of their collars. “We’ll test whether this disrupts their ability to detect the natural magnetic field,” says Benediktová. If pups do use magnetoreception, the magnet could interfere with this sense and change their behavior. For example, they might instead rely more heavily on their sense of smell to find their way. If dogs don’t use magnetic fields to navigate, the collar magnet shouldn’t affect their pathfinding.

Benediktová looks forward to digging deeper. “Dogs are such amazing animals with these great navigational abilities,” she says. “Understanding them better can help people love them even more.”

Benediktová wants to explore further. So she’s planning a follow-up experiment. This time, she’ll attach a small magnet to the dogs’ collars. Will the dogs navigate differently with and without the magnet? “We’ll test whether this disrupts their ability to detect the natural magnetic field,” says Benediktová. If pups do use magnetoreception, the magnet could interfere with this sense. Then their behavior might change. For example, they might use their sense of smell more to find their way. If dogs don’t use magnetic fields, the collar magnet shouldn’t affect their navigation.

Benediktová looks forward to digging deeper. “Dogs are such amazing animals with these great navigational abilities,” she says. “Understanding them better can help people love them even more.”