A new U.S. study of polar bears off Alaska's coasts says faster-moving sea ice brought on by rapid global warming is adding to the animals' physiological stress.
The study by U.S. Geological Survey researchers and others says the already at-risk bears have to burn more calories to stay within their preferred habitat as sea ice drifts.
Research ecologist George Durner says that adds to problems for polar bears in the southern Beaufort Sea.
Researchers there have documented declining body condition, reproduction and survival among polar bears as diminished sea ice gives them fewer opportunities to hunt for seals.
The study concludes that bears must kill one to three more seals per year to compensate for burning more calories on sea ice that carries bears away from their home range.