Today, we’re getting in the winter spirit by spotlighting five remarkable marine animals that depend on cold and icy environments to thrive. 1. Narwhals Narwhals are often called the “unicorns of the sea” because of their long, spiraled tusk . Here are a few more fascinating facts about them: Believe it or not, their tusk is actually a tooth used for sensing their environment and sometimes for sparring. Narwhals are whales. While many whale species migrate south in the winter, narwhals spend their entire lives in the frigid waters of the circumpolar Arctic near Canada, Greenland and Russia. Sea ice provides narwhals with protection as they travel through unfamiliar waters. 2. Walruses Walruses are another beloved Arctic species with remarkable adaptations for surviving the cold: Walruses stay warm with a thick layer of blubber that insulates their bodies from icy air and water. Walruses can slow their heart rate to conserve energy and withstand freezing temperatures both in and out of the water.…