Climate change is threatening polar bears along Hudson Bay with starvation by shortening their hunting season, according to a study by the Canadian Wildlife Service published in the journal Arctic. In the past 20 years, the sea ice season on Hudson Bay has been reduced by three weeks, giving the bears in the area less time to hunt on the ice for their main food source, the ringed seal. The shorter season has resulted in bears returning to the mainland with a lower body mass and females giving birth less often, the researchers say. Bears have also been traveling more frequently to areas populated by humans, searching for food. A significant decline in the Hudson Bay polar bear population has not yet begun, but if current trends continue, a downturn will likely be seen in the next 20 to 30 years, said Gary Cook of Greenpeace.