Polar Bears

Polar Bears

2005

Polar bear or Ursus maritimus , sympathetic white Teddy bear and formidable predators , is one of the most remarkable animals in the world . Among North America 's largest land carnivores , polar bears are taller than grizzlies and can weigh more than 1 ,500 pounds . Their claws are needle sharp for traction on the ice and for subduing seals , their canines longer than those of grizzlies and ideally suited to tearing apart flesh . Polar bears are strong enough to pull a beluga whale out of the water , patient enough to

wait hours above a seal 's blowhole , and canny enough to hide their black nose with a paw as they stalk an unwitting seal . They are capable of killing humans and have done so often . Like sharks , they are attuned so perfectly to their environment that we humans can only be clumsy and ineffective interlopers in their world . Moreover , even to most animals , a of life on the Arctic 's frozen seas sounds pretty grim . Not only is it dark for much of the year , bur icy winds , subzero temperatures , and fierce blizzards are the rule . For the polar bear , however , that environment is a happy home In fact , of all the Earth 's bears , only the polar bear lives exclusively in the Arctic region , justly earning such nicknames as the sea bear , the ice bear , and lord of the Arctic

Because its polar bear 's life is so intimately connected to oceanic environments , scientists consider Ursus maritimus a marine mammal and place it in a group that includes whales , sea otters , and walruses Exactly how the polar bear adapted to the sea ice is something of a mystery , though in scientific circles it is generally accepted that it evolved from the grizzly bear line . This might have happened during the mid-Pleistocene period 200 ,000 to 250 ,000 years ago (Struzik , 39 , when a population of grizzly bears became isolated by an advancing ice sheet Secluded in an environment filled with seals and no other predatory competitors , these opportunistic feeders discovered a wide-open niche and evolved into the modern polar bear

As generations of sea bears adapted to their new environment and life as pure carnivores , their bodies went through dramatic change . Teeth became sharper for shearing of hide and flesh claws became shorter sharper , and strongly curved , to permit a better grip on ice and prey . Most noticeably , their fur became a creamy white , to better blend with ice and snow . Polar bears also have black skin , and blubber , a thick layer of fat below the skin that provides insulation for their bodies and allows them to withstand arctic temperatures . Now North America 's largest land carnivore , adult males average around 1 ,000 pounds but may weigh up to 1 ,700 pounds and , standing on hind legs reach more than 11 feet tall . Adult females , though considerably smaller , may reach 700 pounds . Evolutionary changes also are evident in other aspects . For instance , most female polar bears have...