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| credit: Edward J. Cox |
Scientists at the US Geological Survey (USGS) say polar bears are unlikely to adapt to a terrestrial diet. Survival rates in western Hudson Bay where the lack of sea ice is forcing bears to stay on land, are dropping despite observed feeding on land. This is not surprising news. Most animals evolve biologically into relationship along with their prey. Polar bears depend heavily on
energy-rich, fatty seal meat. Their prey targets do not haul out onto land, so when their is no sea ice to provide a hunting platform, the great white bear lives on its stored fat. While polar bears have been observed feeding on land since the 1400s, caribou carcasses, the occassional whale carcass, goose eggs and berries cannot provide enough energy. The study states that all of the goose eggs in the Hudson Bay region could only support the 900 local bears for a day and a half. On land polar bears must compete with an evolved land-based preditor, the brown bear. Despite being twice their size, brown bears have been seen chasing a polar bar away from a carcass. The government study published in
Frontiers of Ecology confirms findings made earlier by Polar Bears International, a conservation group. While polar bears may be feeding on land, what they are eating is not as nutritionally valuable as seal meat. It is generally expected that two-thirds of the world's polar bears will die by midcentury if humans do not mitigate the rise in greenhouse gases.