Poles apart

Animals of the Arctic and the Antarctic, and why the two faunas look nothing alike.

• Polar BearUrsus maritimus
• Emperor PenguinAptenodytes forsteri
• NarwhalMonodon monoceros
• WalrusOdobenus rosmarus
• ReindeerRangifer tarandus
• Harp SealPagophilus groenlandicus
• Vulpes lagopus
• Blue WhaleBalaenoptera musculus

About this list

The Arctic is an ocean surrounded by land; the Antarctic is land surrounded by ocean. That single geographic difference explains most of the contrast between their faunas. Land mammals walked north into the Arctic and stayed — bears, foxes, reindeer, wolves. None of them ever reached Antarctica, which has no native land vertebrates at all.

Penguins, correspondingly, are a Southern Hemisphere group and no wild penguin has ever met a polar bear.