Animal migrations rank among nature's most impressive phenomena. Driven by seasonal changes, breeding needs, and food availability, these journeys can span thousands of miles and multiple generations.
The Arctic tern holds the distance record, traveling from Arctic to Antarctic and back—roughly 44,000 miles annually. Over a 30-year lifetime, a tern flies the equivalent of three round trips to the Moon.
Monarch butterflies complete multi-generational migrations. Butterflies that fly south to Mexico in autumn have never made the journey before—their great-great-grandparents did. Yet they return to the same trees their ancestors used, navigating by sun position and Earth's magnetic field.