Snow camouflage as Hugh B. Cott have echoed his observations, adding that other animals of the Arctic such as musk ox, moose, reindeer, wolverine and raven never become white "even in the coldest parts of their range". Cott noted that both animals that hunt, like polar bear and stoat, and prey animals like ptarmigan and mountain hare, require camouflage to hide from prey or from predators respectively. There is little experimental evidence for the adaptiveness of white as camouflage, though the ornithologist W. L. N. Tickell, reviewing proposed explanations of white plumage in birds, writes that in the ptarmigan "it is difficult
Arctic Report Card video that summarizes the Report Card. In 2015, Arctic sea extent at the end of the winter was the lowest during the satellite record and the winter maximum occurred 15 days earlier than in the past. The sea ice minimum at the end of summer was the 4th lowest extent on record. These changes are having profound impacts in both the marine and terrestrial ecosystems and in sea surface temperatures. Arctic Report Card The National Oceanic and Atmospheric Administration's Arctic Report Card presents annually updated, peer-reviewed information on recent observations of environmental conditions in the Arctic relative to historical records.