Monarchs - The Incredible Journey

​Danaus plexippus

Happy Monarch Migration Season, everyone!

Monarchs are one of the most instantly recognizable butterflies, in my opinion, unless you are looking at a Viceroy or a Painted Lady, or any number of other mimics. Because Monarch caterpillars eat milkweed, the adults are toxic to birds, so looking like a prey item that will make you sick helps similar-looking butterflies not get eaten.

But back to migration! The Monarch migration is one of the most enigmatic events in nature. When birds migrate, one individual is born, spends spring and summer in one place, travels in fall to where they overwinter, returns to the area where they were born, raises their own brood, and the cycle continues for the life of that individual. In Monarchs, it takes four generations to complete a migration.

Generation one is born somewhere in the United States, living two to six weeks, during which time they mate and lay eggs of generation two. Depending on whether these are Eastern or Western monarchs, populations one and two may venture east or north. Generations two and three tend to stay in the summer breeding grounds. Generation three lays the eggs of generation four, which is significantly larger than those of earlier generations. Gen Four enters reproductive diapause, meaning they don’t mate and lay eggs right away. They begin the migration to Mexico if they are in the east or Coastal California if they are in the west. This generation lives for nine months! The oyamel fir forests in central Mexico have become an ecotourism hotspot to see thousands, if not millions of Monarch butterflies alighting in the trees. In the spring, Gen four returns to the north, and the cycle repeats.

How does this happen? How is Gen three able to produce an enormous Gen four? How is Gen four able to live so long? How do they know where to go? I have several friends involved in Monarch research, and the short answer is, no one really knows.

One thing we do know is Monarch populations are drastically declining due to habitat loss and insecticide use. You can support Monarchs by planting native milkweed. Native is the key. Please avoid tropical milkweed. Also, don’t use insecticides. This will help not just Monarchs, but loads of other species.

Keep your eyes peeled for Monarchs heading south and wish them a successful journey!

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