A bear is a large mammal of the order Carnivora, family Ursidae. The adjective, ursine, is used to describe things of bearlike nature. Common characteristics of bears include a short tail, excellent senses of smell and hearing, five un-retractable claws, and long, dense, shaggy fur. Bears have a large body with powerful limbs. They are capable of standing up on their hind legs. They have broad paws, long snouts, and round ears. Their teeth are used for defense and tools and depend on the diet of the bear. Their claws are used for ripping, digging, and catching. Bears live in a variety of habitats from the tropics to the Arctic and from forests to snowfields. They are mainly omnivorous, although some have a more specialised diet, such as polar bears. They eat lichens, roots, nuts, and berries. They can also go to a river or other body of water to capture fish. Bears will commonly travel far for food. Hunting times are usually in the dusk or the dawn except when humans are nearby. Some of the large species, such as the polar bear and the grizzly bear, are dangerous to humans, especially in areas where they have become used to people. For the most part, bears are shy and are easily frightened of humans. They will, however, defend their cubs ferociously. A bear is a large mammal of the order Carnivora, family Ursidae.