Monarch Migration and Metamorphosis | Incredible Animal Journeys | National Geographic

In Texas, the monarch is close to exhaustion. With her last reserves, she's seeking out the perfect spot to lay her eggs. Using her amazing sense of smell, she's on the hunt for milkweed, the only food her babies will eat. It's a plant which was once abundant. But now over three quarters of the state is farmland, choked by pesticides and weed killers. For a butterfly, it's effectively a desert.

It's not just farms that have replaced wild landscapes. Reaching the suburbs of Austin, she's running on empty. But incredibly, in flight from over 400 feet away, she's found the needle in the haystack. This backyard has exactly what she needs for her eggs. She lays hundreds on milkweed specially planted to help migrating monarchs. But she'll never meet her babies. Before they even hatch, she takes her last breath. Her mission is complete.

This is the true miracle of the monarch migration. It's not a marathon. It's a relay race. After about four days, her caterpillars hatch in the perfect nursery, surrounded by food. And that's all this little bug has on her mind. Milkweed is poisonous, yet she's not only immune. She's using it for her own defense, storing the deadly chemicals in her body. She makes herself toxic, wearing bright colors as a warning signal.

In just two weeks, she'll eat and grow. And eat. And grow. Until she's 3000 times bigger. Spinning sticky silk to hang from, she forms a chrysalis. Over the next ten days, she breaks herself down into a kind of genetic soup. Before putting herself back together and emerging as a butterfly. She's her mother's daughter, born with the same mission and the same built-in G.P.S.