Are Polar Bears & Brown Bears Cousins?
When is a bear not a bear? When it is its cousin!
For some time now, scientists have thought that polar bears established as their own separate species only about 150,000 years ago. Earlier studies had focused mainly on mitochondrial DNA (mtDNA), which is passed from a mother to her offspring. They had concluded that polar bears were a recently evolved type of the northern brown bear and that white fur evolved in response to their arctic habitat.
Recent studies however suggest that the evolution of polar bears and brown bears as separate species occurred nearly 600,000 years ago. Axel Janke and Frank Hailer, researchers from the Biodiversity and Climate Research Center in Frankfurt, Germany compared genetic sequences from 19 polar bears, 18 brown bears and 7 black bears in a more comprehensive study.
The Sea Bear
Polar bears also known as Ursus Maritimus (Sea Bear), live along shores and on sea ice in the Arctic. There are about 20,000 to 25,000 polar bears living worldwide today. When sea ice forms over the ocean in cold weather, many polar bears head out onto the ice to hunt seals. When the warm weather causes the sea ice to melt, polar bears are forced to move back toward shore.
Polar bears, the largest among bears, are also the largest predators on land. When they hunt, they often rest silently at a seal's breathing hole in the ice, waiting for a seal in the water to surface. Once it comes up, the bear will spring and sink its jagged teeth into the seal's head.
Amazing Fur Facts
Polar bears have fur and skin that allow them to absorb sunlight for warmth. Their blubber, or fat, insulates them in cold water. Did you know that a polar bear's fur is not white? Each hair is a clear hollow tube. Polar bears look white because the hollow hair reflects the light. They have black skin under their clear fur!
On sunny days, the tubes trap the sun's infrared heat and keeps the bear warm at 98 degrees F when they're resting. Polar bear fur is oily and water repellent. The hairs don't mat when wet, allowing the polar bears to easily shake free of water and any ice that may form after swimming.
Humans are the polar bears only predator. The polar bear's habitat is under threat with man moving into the Arctic region to mine for oil and other resources. Oil spills are particularly dangerous. Besides, human activity and the accelarating threat of global warming is reducing the ice shelves that these bears have left to make their homes.
At this time polar bears are regarded as endangered and vulnerable. Countries around the world are working to protect them.