How do eider ducks and musk oxen survive year round in the Arctic?

Eider ducks survive year-round in the Arctic by adapting to the extreme cold with their thick layers of insulating feathers, which provide Excellent thermal protection. They also rely on a diet of marine invertebrates and can dive underwater to forage for food. Musk oxen, on the other hand, have a thick, shaggy coat made of long guard hairs and a dense undercoat called qiviut that insulates them against frigid temperatures. They graze on grasses, mosses, and lichens, and their social behavior helps them survive harsh conditions by forming protective groups.