Comments: Most active during the first third of the day (DeMaster and Stirling 1981). Pregnant females are dormant in winter dens from autumn to spring, when young are able to survive outside. Variable snow and ice conditions determine when females enter and exit den sites (Amstrup 2003). In the Beaufort Sea, den entry dates averaged mid-November and den exit dates were late March/early April (Amstrup and Gardner 1994 in Amstrup 2003). Mean den entry for the Canadian Arctic was September 17 and mean den exit March 21 (Messier et al. 1994, in Amstrup 2003). Molting commences in April to May and shorter summer coats are achieved by late summer (Amstrup 2003).