Black bears, polar bears, and koalas are all different animals with different behaviors. Here are some of the main differences:

- **Black bears** are mostly solitary and active at night and around dawn and dusk. They are excellent climbers and can escape from threats by going up a tree. They are usually less aggressive than grizzly bears and more tolerant of people, but they can still cause injuries if provoked or threatened. They feed on a variety of plants and animals, but prefer berries, nuts, and insects.
- **Polar bears** are also mostly solitary, but they are active throughout the year. They are strong swimmers and spend over 50% of their time hunting for seals on the sea ice. They are more likely to defend themselves when threatened than black bears, especially females with cubs. They have a thick layer of fat and fur to keep them warm in the Arctic environment. They feed almost exclusively on marine mammals, such as seals and walruses.
- **Koalas** are not bears at all—they are marsupials, meaning they have a pouch to carry their young. They are mostly nocturnal and spend up to 20 hours a day sleeping in eucalyptus trees. They feed on eucalyptus leaves, which are toxic to most animals, but they have a special digestive system to cope with them. They are not very intelligent and have a small brain relative to their body size. They can be aggressive if disturbed or threatened, but they can also be affectionate if tamed or trusted.
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