The incredible journeys of migratory animals
It's hard to imagine a creature as tiny and fragile as a butterfly undertaking epic migratory journeys. And yet, surfing air currents, the monarch butterfly can travel up to 3,000 kilometers. In summer, they're at home in northern regions of the US, but when temperatures fall, they head south to California or Mexico to overwinter. Roosting together in large numbers helps them keep warm all year.