The Miraculous Monarch Migration

During an early September evening, the annual migration of Monarch butterflies paid us a personal visit. For 90 minutes, frequently at the rate of at least 50 per minute,  Monarchs  zigged and zagged like birds above the pine trees, skimmed close to the sand dunes and skittered low along the shallow shore of Lake Michigan. Some passed almost within arm’s reach.

This was the first leg of a 3,000 mile roundtrip relay race to a mountain region of moderate temperatures in central Mexico, where Monarch butterflies from all across North America huddle up in clusters and “rest” for the winter on the branches of the native oyamel fir trees, which are sacred to locals.

While it is a “super-generation” of Monarchs which makes the southern trip in the autumn, several generations team up for the return trip to Michigan and other summer destinations in the US and Canada. They stop every few days to mate and lay eggs. In a few days the black, gold and white larvae hatch and feed on milkweed, then form chrysalises, and finally transform into adult butterflies which fly the next leg of the epic northern migration.

The Monarch — apparently named by early American settlers to honor King William, Prince of Orange (acknowledging the butterfly’s dominant color) — is the only butterfly known to make a two-way migration like birds do. Departure from the north is triggered by diminishing daylight, declining temperature and the quality of milkweed plants, the Monarch caterpillar’s sole source of food.

Declining milkweed growth due to disease, as well as poisoning from human efforts to eradicate weeds and insects, is linked to declining Monarch butterfly population of the past several decades. . .which is why last month’s show along the shore of Lake Michigan was more than special. It was almost a miracle.

To monitor our annual Monarch migration along this “central flyway” — there are also Monarch migrations along an “eastern flyway” to and from the Carolinas and beyond as well as a “western flyway” along the Pacific coast — visit journeynorth.org.

JER