Across mountains, forests, oceans, deserts, and grasslands, millions of animals are constantly on the move.

They follow routes that can stretch for hundreds or even thousands of miles.

Some are visible from the ground.

Others are hidden beneath the ocean.

Some have existed for generations.

And some are so precisely followed that animals seem to know exactly where they are going.

These are Earth's great animal highways.

In The Great Animal Highways That Cross the Planet, we explore the extraordinary migration routes that connect ecosystems across the world and reveal how animals navigate an ever-changing planet.

From massive herds crossing African grasslands to birds traveling between continents, we follow the routes that animals use to find food, water, breeding grounds, and safer e ...