premise: The polar bear is the worlds largest land carnivore and also the largest species of bear, along with the Kodiak bear. The polar bear is on average twice as large as the Siberian tiger and adult males weigh between 350-700kg in the wild. Adult females are roughly half the size, weighing between 150-250kg. Polar bears are insulated with up to 10 cm of blubber, which causes them to overheat at temperatures above 10 C. Unlike brown bears, polar bears are unlikely to become obese in captivity, likely due to warm conditions in most zoos. Polar bears are excellent swimmers and individuals have been seen on open arctic waters as far as 300 km from land.
hypothesis: Polar bears in captivity are much larger than those in the wild.