Polar bears live on frozen sea
The POLAR BEAR is counted as a marine mammal, because it spends most of its life on sea ice rather than land. It hunts by waiting beside holes in the ice for seals to come up to breathe, and it can smell a SEAL from more than a kilometre away. When the ice melts in summer, many bears have to go ashore and live off their fat until it freezes again.
Its fur is not actually white. Each hair is transparent and hollow, and scatters light so the coat looks white. Underneath, the bear's skin is black, which helps soak up warmth from the sun. Polar bears and penguins never meet in the wild: polar bears live only around the Arctic, and penguins almost entirely in the southern hemisphere.
Reindeer eyes change colour
REINDEER and CARIBOU are the same species, with the European name and the North American one. Their eyes change with the seasons: in the endless light of summer the reflective layer at the back is golden, and in the long dark of winter it turns deep blue, which helps them see in very low light. They are the only deer in which both males and females grow antlers.
The STOAT and the ERMINE are the same animal too. In summer it is brown with a black-tipped tail; in the far north its coat turns white in winter, except the tail tip, and in that coat it is called an ermine. The ARCTIC FOX changes colour in the same way.
Lemmings do not jump off cliffs
The idea that LEMMING swarms throw themselves over cliffs comes largely from a 1958 Disney nature film, White Wilderness, which showed lemmings plunging into the sea. The scene was staged: the lemmings were brought in and pushed. Real lemming populations do boom and crash every few years, and migrating lemmings sometimes drown crossing water, but not deliberately.
The Arctic TERN makes the longest migration of any animal, flying from the Arctic to the Antarctic and back every year — tens of thousands of kilometres — so it sees more daylight than any other creature. The SKUA steals food from other seabirds in mid-air, and the PUFFIN can carry a dozen small fish crosswise in its beak at once.
Tusks, tiny krill and the rest
A WALRUS uses its long tusks to haul its heavy body out of the water onto the ice, and its whiskers to feel for clams on the seabed. The NARWHAL and BELUGA live in Arctic waters year round, and the ORCA hunts in both polar oceans. In the south, KRILL, shrimp-like animals a few centimetres long, swarm in such vast numbers that they feed whales, seals and PENGUIN colonies. The male emperor penguin keeps his partner's single egg balanced on his feet, under a fold of warm skin, through about two months of Antarctic winter darkness, huddling with thousands of other males against the wind and eating nothing at all until the chick hatches.
The rest of the grid holds the SNOWY OWL, the WOLVERINE, the LYNX, the MOOSE and the sled-pulling HUSKY. Our Arctic page explains why the north is a frozen ocean and the south a frozen continent.