They lived through the ice age. Can the mighty musk ox survive the heat?

Built like a small bison, weighing as much as a grand piano and covered in thick, shaggy coat, the musk ox is one of the most distinctive species in the high Arctic. But from a hill on Greenland’s tundra, they seem impossible to find.

Each bush, rock and clump of grass resembles a mass of wool and horns in the blustery chill on the edge of the island’s enormous polar ice cap. Scanning the shimmering landscape with binoculars, Chris Sørensen looks for signs of movement.

“See that black dot over there in the orange grass? That could be one,” says the station manager at Kangerlussuaq International Science Support (Kiss), shuffling back towards his car.

“But it could also be a rock,” he says. As we approach the dot, it quickly becomes clear that it is, unfortunately, a rock.

Musk oxen are relics of the ice age, adapted to thrive in pitch-black polar winters where temperatures can stay below -20C (-4F) for months. They give birth as the light returns for the brief Arctic summer, ready to take advantage of the 24-hour grazing days before the light disappears once again. Often boxed in by ice and geography in isolated populations, they are among the world’s most inbred mammals.

More than 20,000 musk oxen live around Kangerlussuaq at the end of a 120-mile fjord, which was once home to Greenland’s main international airport – a converted second world war American airbase – until it was moved to the capital, Nuuk, in December.

In the 1960s, 27 of the animals were introduced to the area from their native territories farther north. They thrived, and now underpin a booming trophy-hunting industry, as well as providing a vital food and economic resource for Indigenous communities. The soft, lightweight underlayer of wool – qiviut – is among the warmest natural fibres, with scarves and hats sometimes costing hundreds of pounds.

Officially, musk oxen are classified as a species of least concern on the IUCN red list of threatened species. But in a warming world, rising temperatures are posing new tests of their resilience, raising concern among scientists about the survival of many fragmented populations.

Disease and parasites – turbocharged by the changing climate – are on the rise in much of the musk ox’s range. A 2020 study of the Canadian Arctic islands found that lungworms, which cause breathing difficulties and weakness, are increasing.

Most worryingly, say researchers, is the spread of the Erysipelothrix rhusiopathiae bacteria – a common infection in farm animals – which has high mortality rates among Arctic mammals.

In the Canadian Arctic islands, the world’s largest musk ox populations have declined by more than half since the early 2000s, wiping out thousands of the mammals.

Prof Susan Kutz, a veterinary parasitologist at the University of Calgary and a longtime researcher of musk oxen, says: “Climate change is exacerbating the multiple challenges that musk oxen already have to deal with. We know that the Arctic is warming at four times the rate of the rest of the world. I think it is increasing their susceptibility to new diseases.”

“I don’t think musk oxen [have] a guaranteed future,” she says. “There’s a lot we don’t know. Populations grow and then they decline. The hope is that they can decline and stay stable, not disappear.”

So far, the disease has not reached Greenland’s musk oxen, which are protected by their geographic isolation. But there are fears that the disease could be spread to the region by birds and other Arctic mammals.

Prof Niels Martin Schmidt, an Arctic ecologist at Aarhus University in Denmark, says the climate crisis is having a noticeable impact. The herds he studies in Greenland– among the most northerly in the world – are pushing even farther north as temperatures warm.

“The east coast of Greenland is super-isolated. That’s why we don’t see this spillover of diseases from southern latitudes yet, at least. So the main threat in that area is the unstable winter climates that will slowly push the musk ox north,” says Schmidt.

“In the short term, that is not bad per se, because there will be suitable area farther north; it’s a huge piece of land. But ultimately, there is no more land at some point, and then they fall into the ocean. It goes in one direction. The Arctic is becoming smaller and smaller all the time,” he says.

After more than an hour of driving in search of a musk ox, we are close to giving up. We rumble alongside a dwindling river fed by meltwater from the nearby Russell Glacier. Strangely shaped rocks and patches of colour in the landscape provoke several more false alarms.

Then, in the shadow of the ice sheet, we spot a group of eight musk oxen huddled together. Two members of the herd battle playfully with each other on the riverbed, which will soon run dry as temperatures drop.

We stand and watch the shaggy masses move back towards the tundra, where they will become invisible once again in their surroundings, feeding until the Arctic night returns.