What is the largest land carnivore?

The polar bear, up to about 700 kilograms, though the Kodiak brown bear runs it close and the two are genuinely difficult to separate on record weights. Polar bears are classified as marine mammals, which is the more interesting fact - they hunt almost exclusively from sea ice, and their scientific name, Ursus maritimus, means sea bear.

Their fur is not white. Each hair is a hollow transparent tube, and the animal looks white for the same reason snow does, by scattering light; the skin underneath is black. Bears kept in humid zoo climates occasionally turn green when algae colonise the inside of those hollow hairs.

The diet is almost pure fat - mainly ringed seal blubber, which is the most energy-dense food available and the only thing that supports an animal that size in the Arctic. That is also the vulnerability. A polar bear cannot outswim a seal in open water; it needs ice to wait beside a breathing hole. As the ice season shortens, bears spend longer on land fasting, and the body condition of the western Hudson Bay population has been declining measurably for decades. Their livers are also so rich in vitamin A that eating one can kill a person, which Arctic explorers discovered the hard way.