Due to climate changes, Arctic ice is breaking up earlier in the spring, and its area is decreasing. This is creating problems for polar bears that make their homes off northern Alaska and in Hudson Bay.
Polar bears off Alaska normally hunt and raise their young on ice sheets that float on the ocean. But as the ice has melted, the polar bears have been forced to spend more time on land. There, they have begun to frequent beaches, feeding on the remains of whales caught by native hunters. For polar bears, this food is less nutritious than seals that they normally catch on ice sheets. The shrinking(减少) ice has also forced more polar bears into the ocean. In the past, they only had to swim short distances between ice sheets. But as the ice has shrunk, polar bears have been forced to swim longer and longer distances in the open ocean. This poses a severe danger during rough weather, and an increasing number of drowned polar bears have been observed.
In Hudson Bay, the ice breaks up three weeks earlier in the spring now than it did 20 years ago. Polar bears in Hudson Bay fast(禁食) during the summer, waiting for ice to form in the fall to hunt. Every year, the summer gets longer, and the bears get skinnier. Over the past 25 years, the average weight of the female bears has dropped to 68 kg. This loss affects their ability to reproduce, and already the number of births has dropped by 15 percent. Unless the bears can learn to survive these climate changes, these giants of the ice may one day disappear.
