Epic flights, adventurous sea journeys, and exhausting road trips all play a key part in the lives of many species. These empires travel in search of food, shelter, or a mate. But booking and organizing travel is no easy feat when those plans involve hundreds - even thousands - of individuals. In this episode, we examine caribou, elephant seals and monarch butterflies.

pt. 1. Migration: Caribou -- pt. 2. Migration: Elephant Seals -- pt. 3. Migration: Monarch Butterflies.