A Breathtaking Swarm of 100 Million Butterflies Earths Great Seasons BBC Earth

Deep in the forests of Mexico, millions of monarch butterflies spend their winter sheltered from the cold. Once spring arrives, it is time for them to awaken and take to the skies, in what is truly an amazing spectacle.

Taken from 'Earth's Great Seasons' (2016).

The BBC's Natural History Archive celebrates the extraordinary nature of the four magnificent seasons on Planet Earth, and how animals and plants rise to the new challenges they bring. In each episode, we visit a different season, each with its own magical and dramatic personality, and reveal how different animal characters must find their own extraordinary ways to make it through.

Narrated by Andrew Scott.

Welcome to BBC EARTH! The world is an amazing place full of stories, beauty and natural wonder. Here you'll find 50 years worth of entertaining and thought-provoking natural history content. Dramatic, rare, and exclusive, nature doesn't get more exciting than this.