It’s hard to miss a musk ox: It looks like a buffalo decked out in a hairy fur coat. And yet this easy-to-spot giant, which lives on tundras from Siberia to Greenland, is still surprisingly mysterious.

“Here is the largest land mammal of the polar zones, but we hardly know anything about musk oxen,” said Joel Berger, a wildlife biologist at Colorado State University and a senior scientist at the Wildlife Conservation Society.

Dr. Berger has studied musk oxen in Alaska for nearly a decade, and on Thursday in the journal Scientific Reports, he and his colleagues reported a disturbing finding: Musk oxen are unexpectedly vulnerable to rapid climate change in the Arctic.

In a warming landscape, pregnant female musk oxen may struggle to find enough food for their unborn calves, the researchers found. Their undersized offspring may die young or fail to produce many calves of their own. In places, musk oxen may disappear altogether.