A young Arctic fox has walked 2,175 miles (3,500 kilometers) in just 76 days, traveling by paw from Norway's Svalbard islands to northern Canada in an epic journey that astonished the scientists who were tracking her.
The fox's adventures were recorded by researchers from the Norwegian Polar Institute (NPI) and the Norwegian Institute for Nature Research (NINA), who describe them in a blog post and a paper published in the journal Polar Research.
"We didn't think it was true," NPI researcher Eva Fuglei says in a statement, explaining the scientists' initial disbelief about the data. But the fox couldn't have hitched a ride on a boat, due to the region's sea ice, and there weren't many other likely explanations for how she could travel so far so fast — aside from her feet. "So we just had to keep up with what the fox did," Fuglei says.
The researchers had outfitted the juvenile fox with a satellite tracking collar in March 2018, then released her into the wild on the western coast of Spitsbergen, the main island of the Svalbard archipelago. She headed east through Svalbard, then began hiking north across sea ice on the Arctic Ocean. She reached Greenland 21 days later, her tracking data showed, which was already an impressive expedition of about 940 miles (1,512 km) in three weeks.
She was just getting started, though. She went on to walk another 1,200 miles (1,900 km) at a blistering pace, including a brisk trot across the Greenland ice sheet, before finding her way to Canada's Ellesmere Island just 76 days after leaving Spitsbergen.
The fox averaged 28.8 miles (46.3 km) per day during its 76-day trek from Svalbard to Canada's Ellesmere Island. (Map: Arnaud Tarroux/NINA)
This journey was likely motivated by hunger, the researchers say, as Arctic foxes are known to travel long distances during leaner months in search of food. And while this fox walked farther than most, what really amazed the researchers was her speed.
She covered an average of 28.8 miles (46.3 km) per day, they report, including a peak of 96.3 miles (155 km) in a single day as she crossed the Greenland ice sheet. That is "the fastest movement rate ever recorded for this species," the researchers write, noting it's 1.4 times faster than the previous one-day record of 70 miles (113 km), set by an adult male Arctic fox in Alaska.
This young fox might have hustled through Greenland because of limited food options there, the researchers explain, although she also slowed down significantly a couple times during the journey. She might have waited out bad weather by curling up in the snow, they note, or might have lingered because she finally came across a good food source.
It's unclear what the fox is up to these days, since her tracking collar stopped sending data in February 2019. She has presumably changed her diet, though, since Ellesmere Island foxes mostly eat lemmings, unlike the seafood-centric diet of foxes in Svalbard.
This study is part of a broader, long-term research project called Climate-ecological Observatory for Arctic Tundra (COAT), which "aims to unravel how climate change impacts Arctic tundra food webs." Temperatures in the Arctic are rising at double the global average, causing a cascade of changes for many species and ecosystems. Arctic sea ice is now shrinking by about 13% per decade, according to NASA satellite data, and the 12 lowest seasonal minimums have all been recorded in the last 12 years.
Similar to isolated fox populations in Iceland and on small islands in the Bering Strait, which were previously linked to other populations by sea ice, Svalbard's foxes might soon find this kind of journey is impossible, researchers say.