Brown bears from northern hemisphere forests probably simply walked into the frozen realm of the Arctic. Meanwhile, Antarctica is a land mass, surrounded by an ocean. It's thought that ancestors of today's penguins could fly. They might have flown to Antarctica.
Antarctic penguins have very special requirements for feeding and breeding.
So in the Arctic, even if they could find the right food, penguins would be extremely vulnerable to land predators. Meanwhile, there might be some denning problems for female polar bears transported to Antarctica. But these bears might do extremely well feeding on Antarctic penguins and seals that have never known a predator on land. For today, that's our program. I'm Deborah Byrd with Joel Block for Earth and Sky.