Polar bears occur at low densities throughout their range and are most abundant in shallow water areas near shore or where currents or upwellings increase biological productivity near ice areas associated with open water, polynyas or lead systems. Polar bears are not as abundant in the high central arctic over deeper waters of the polar basin.

Seasonally, in the summer open water season in the Canadian arctic islands and Svalbard, and in recent years during the fall in northern Alaska and Russian Chukotka, polar bears may be found on land in higher densities.

Breeding occurs in March to May, implantation is delayed until autumn, and birth is generally thought to occur from late November to mid-January. Although some cubs are born in earth dens, most births occur in snow dens that may be occupied between 5?6 months during the maternal event. In Alaska the maternal dens are located on the offshore sea ice. Only pregnant female polar bears den for this protracted period of time, during which time they rely on fat stores for energy and sustenance. The average litter size is less than two. Cubs are dependent upon mothers until after the start of their third year of life. Age of first reproduction is normally 5?6 years for females. These factors contribute to the low reproductive potential for the species.