Monarch’s Incredible Migration About to Begin!
Each year, between August and November, we need only look skyward to witness one of nature’s most incredible migrations. Tens of millions of Monarch butterflies that spend the summer east of the Rocky Mountains fly to Central Mexico. Here, about 70 miles west of Mexico City, Monarchs survive the winter in 12 mountaintop fir forests at 10,000 feet elevation.
The Monarch is the only butterfly that migrates north and south very long distances as many birds do. This unique annual pilgrimage was only recently discovered, in 1975. Conservationists have worked ever since to protect this natural spectacle of evolution and adaptation, which depends both on protecting ecological health in the USA and conserving the relatively small land area in Mexico where all of our eastern Monarchs spend the winter (except for a small additional population in Florida).
The Monarch’s journey is even more amazing when you understand the details of their “multi-generation” migration cycle. Unlike migratory birds, no single Monarch makes the entire round trip because their normal eight-week lifespan is too short. The Monarchs that overwinter in Mexico do not reproduce until after they start heading north, usually reaching Texas and Oklahoma, sometime in February and March. Their offspring (“second generation”) continue heading north throughout their two month life, as do the third and fourth generations, each generation making it further north until they reach northern USA and Canada. Millions and millions of Monarchs are produced along the journey north. As fall and cold weather approaches, the last generation of the summer enters into a special non-reproductive phase, which allows these individuals to live seven months, or more. It is these longer living, fourth generation Monarchs that return to Mexico to repeat the cycle. The mystery to scientists is how do these butterflies separated by three generations know how to return to the same 12 mountaintops in Mexico!
The female Monarchs lay their eggs on a variety of milkweeds, whose leaves the caterpillars feed on for two weeks after hatching from a four-day incubation period. Next, after a two-week pupal stage, the adult emerges from its chrysalis. The adults feed on nectar from milkweeds, butterfly weed, golden rods, and other plants. If you wish to attract Monarchs to your property planting milkweeds is the best idea, as it feeds both adults and caterpillars. You can easily learn to recognize the eggs, caterpillars, and chrysalis on the milkweed plants. Look for them!
Of the 142 species of butterflies that live in New York State, the Monarch is my favorite. So, it is disappointing to me that there seems to be very few this summer at Teatown or in the Hudson Hills and Highlands? Leave a comment below if you have noticed the same paucity of Monarchs this summer and share your observations about migrating Monarchs. Who will be the first to spot a migrating Monarch this season?
Now that August is here, I will be keeping an eye to the sky for Monarchs. You can tell when they are migrating (as opposed to flying for nectar or mating), because they seem to be moving in a purposeful straight path. Also, if you follow a migrating Monarch toward sunset – and if you are lucky – you might discover a roosting tree with dozens, even hundreds, of resting butterflies. If you want to learn more about Monarchs and follow a citizen-scientist project to track their migration visit the Journey North and Monarch Watch websites. Better yet, take your family on a trip to Cape May, New Jersey, in September and October to witness thousands of these winged jewels heading south. Enjoy the Monarch migration — it is a miracle that unfolds each year right before our eyes!