Bears hibernate during the winter months in most areas of the world. Duration of winter denning is dependent upon latitude and varies from a few days or weeks for black bears in Mexico to 6 months or more for bears in Alaska (Kolenosky and Strathearn 1987, Haroldson et al. 2002).
On March 17, 2016, History renewed Vikings for a fifth season of 20 episodes, which is set to premiere on November 29, 2017.
It's a series, going ahead, that's ripe for better, more complicated storytelling, but in its first season, Vikings has been a stellar companion to Game of Thrones, a brutal, blood-drenched series quick to get the point and less likely to leave us drifting in a sea of uncertainty from week to week.