At first, the scientists wondered whether it was a mistake.
Just 21 days after leaving the Norwegian island of Spitsbergen, an arctic fox had arrived in Greenland. And in less than three months, it made it to Canada.
The fox averaged nearly 30 miles a day (50 kilometers) - some days, though, it walked almost 100 (160 kilometers).
"When it started happening, we thought 'is this really true?' " said Arnaud Tarroux, one of the researchers who tracked the female fox. Was there "an error in the data?"
The data was real, the scientists decided as the fox kept going. The creature's travels last year, documented in a recent paper, wowed Tarroux and his fellow Norwegian researcher Eva Fuglei, even though the animal is known for its endurance and ability to survive in harsh polar areas.
Scientists already knew that some of the foxes, native to Arctic areas all around the Northern Hemisphere, made long journeys: DNA exchange links far-flung fox populations in areas connected only by sea ice.
But the fox these researchers followed stood out for just how fast it covered more than 2,700 miles (4,350 kilometers) - and shed light on far-north fox sightings that explorers wondered about as far back as the 1800s.
"We didn't really know how they would do that and how long it would take for an individual to do this kind of trip," Tarroux said.
The coastal fox the researchers tracked, also known as a blue fox, landed in Ellesmere Island in Canada on 1 July 2018. Of the 50 or 60 animals the scientists put trackers on for a study, it was the only one that ventured outside of Norway.
The researchers think the fox may have taken off because of a food shortage, but they're not sure. The tracker stopped working in February, so researchers no longer know the fox's whereabouts, but it was last detected on the same Canadian island in the Nunavut territory.
Families can be far-flung and relatively isolated.
Fling back the ball to me.