Polar bears (Ursus maritimus) currently have an IUCN status of vulnerable, meaning the risk of extinction is high. They are considered threatened under the U.S. Endangered Species Act. The range of polar bears extends throughout the circumpolar region, including Alaska, Canada, Greenland, Norway and Russia. Because polar bears spend the majority of their time on the sea ice, they are actually considered to be marine mammals. Their main food source is the ringed seal, which they hunt on the ice or at breathing holes. It is difficult for polar bears to catch seals in the open water, and when the bears are driven to land by receding ice, food is scarce. Overhunting caused a significant decrease in polar bear populations in the 1960s, but this threat has lessened since hunting restrictions have been established. Currently, the primary threat to the survival of polar bears is the loss of sea ice due to climate change. Increasing temperatures have caused sea ice to disappear at record rates, and polar bear populations in many areas are declining.
Read more: http://www.brighthub.com/environment/science-environmental/articles/68967.aspx#ixzz1buFvX0ii
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