This creature is the size of a large dog. It has a pink or reddish nose, rounded ears, and three-toed paws. Its fur is predominantly white, apart from a single black striped pattern that begins at its nose and runs over its forehead along its back. Its thick fur allows it to adapt to cold temperatures, which is crucial considering its habitat.
Although never shown in the wild, there was at least one domesticated polar dog in the Southern Tribe. The mammal appeared to be quite docile, or at least lazy, as seen when it barely opened an eyelid even after all of the children surrounding it pointed to they sky and gasped in excitement when Aang "flew" on his glider.
The natural connections for this animal are to the real life polar bear, or white bear (though the fictional creature is much smaller), and to Alaskan Malamutes and other northern breeds used in Arctic dog sledding.