A male polar bear waits for an ice sheet to form to allow migration in an area about 300km (186 miles) north of the Canadian town of Churchill in this picture taken November 17, 2009. Climate change has turned some polar bears into cannibals as global warming melts their Arctic ice hunting grounds, reducing the polar bear population, according to a U.S.-led global scientific study on the impacts of climate change. Picture taken November 17, 2009. [Xinhua/Reuters]