Polar-bear populations
Polar bear populations fluctuate in response to natural factors such as climate and prey availability. Populations can also be impacted by humans through factors such as hunting, oil spills, shipping, and other activities. Advances in satellite telemetry and other advanced technology have helped researchers track polar bear patterns more definitively, which has greatly enhanced our knowledge of movements and population bounds.
Polar bears have long captured our attention, but probably at no time in the past have they been more in the forefront of the public's attention than today. The international organization, Polar Bears International, predicts that if current warming trends continue in the Arctic, two-thirds of the world's polar bears could disappear by 2050.
Today's heightened interest in polar bears may be due in part to an enhanced understanding of the current global warming at the polar ice caps, as well as polar bear ecology and the recent issues regarding whether they should be considered endangered. Recent efforts to communicate these concerns, research and statistics have been made to the public to help heighten the public awareness.
Results of years of research and studies are now available to an interested public, and efforts to communicate this information to the public have been more effective in recent years than in the past.
Polar-bear ecology
Polar bears are not a single large homogeneous population, but are rather comprised of groups referred to as stocks or populations, which are distributed throughout the Arctic. The first extensive research began in the late 1960s and has made significant progress today. We now have a thorough backdrop of information on population demographics, systematically analyzed data on population boundaries, population movements, population size, reproductive and survival parameters, and other useful information about biological, physiological, and ecological aspects of polar bears.
Research indicates that polar bears do not occur in large numbers. In addition, their ability to replace individuals in the population is very limited and population growth is extremely slow; however, they are long-lived creatures, which helps to offset the low reproductive potential.
Polar Bears in Summer
In summer, sea ice melts first along the heat-absorbing Alaskan coastline. Polar bears find cracks in the ice pack that are narrowly open or thinly frozen over, for hunting seals. Most bears in the Beaufort and Chukchi Seas stay on the main pack to hunt, as it recedes miles from shore. Bears distribute themselves along the ice edges, where they have better access to seals. Outside of the main ice pack, isolated ice floes break into smaller floes or large patches of unconsolidated ice. Bears that are isolated from the main pack or land use these floes like a series of floating islands for hunting or resting. Eventually the floes become too small for a bear, which may have to swim to the main ice pack or to land.
Polar bears in Autumn and Winter
As summer turns into fall, the Arctic begins to cool. During the onset of the long dark winter, virtually all of the Arctic Ocean refreezes. In fall, ice and bears return nearer to shore. As autumn progresses, temperatures cool, and ice begins to form again. Polar bears follow that leading edge of ice south, eventually occupying the shallow waters of the continental shelf, where the seal population is highest. To adapt, polar bears build fat stores necessary for winter survival. Pregnant females particularly fatten in early autumn to fuel their long winter fast and the nursing of their cubs. Later in autumn, they look for winter birthing dens near the coast or on stable ice pack, near good hunting habitat. Long swims between sea ice and shore deplete their body stores, affecting their reproductive success.