The story of Holly, the cat who came home from 200 miles away, is quite amazing. Scientists don't understand how she did it, although they have some ideas to explore.
"Any animal that comes back to the right place after a long travel, or comes back to the same place again and again following a major movement, is amazing," said Martin Wikelski, a migration expert at the Max Planck Institute. (Read about great animal migrations in National Geographic magazine.)
Many animals have a built-in magnetic system, "like a regular compass," said Wikelski, who is also a National Geographic emerging explorer.