Every year it happens, thousands of monarch butterflies migrate southward in search of a more temperate climate. In northern latitudes, the migration may have already peaked, for people in the central and southern states, it’s just beginning, and if you’re in a warm southern climate, the monarchs in your area may not migrate at all. For those living west of the Rockies, the monarch population is heading to coastal California, and if you’re east of the Rockies, the butterflies are taking a longer trip to forests high in the mountains of Mexico.
North American Monarchs are the only butterfly that migrates over such long distances, up to three thousand miles, and they do it every fall and spring. Every year, the butterflies follow the same path, often going to the same exact trees – except each butterfly only makes the two-way trip once. The butterflies that make the trip in the fall are several generations removed from the ones who made the trip the previous fall. It’s a great mystery how the butterflies find the same path each year.
Exactly why monarchs migrate is up for debate. When the butterflies reach their overwintering sites, they eat very little and don’t mate or reproduce the next spring. Migrating monarchs are larger and live longer than those that hatch any other time of the year. A typical monarch will live two to five weeks, eating and reproducing the whole time. The generation that migrates in the fall will live up to nine months and only reproduce at the very end of their life when they take the journey back north.
Sadly, resources for migrating monarchs are diminishing. Overwintering butterflies need shelter and water and logging in Mexico has damaged a number of colony sites. Monarchs need milkweed to lay their eggs on and for nectar; development and pesticide use in the US and Mexico has reduced the availability and suitability of plant life. Climate change is another threat to the monarch’s annual cycle; the butterflies prefer moderate temperatures during winter and sprint recolonization. Higher temperatures could negatively impact both the monarch population as well as the plants on which they depend.
If you have monarchs in your area, or are on a migratory path, the easiest way to attract them to your yard is to plant milkweed. It’s a one-stop-shop for the butterflies, caterpillars eat the leaves, butterflies drink from the flowers and lay their eggs in the leaves. Just remember, the caterpillars will defoliate your plants. This isn’t about looks, it’s about providing a valuable resource for wildlife. Monarch eggs are small white ovals and the caterpillars are green at first, but within a week bear distinct stripes of yellow, black and white. The chrysalis will be green at first, but turns transparent as the butterfly is ready to emerge. Keeping other nectar flowers and a water feature will add to the attractiveness of your yard.
To learn more about monarchs and their migratory cycle, check out Monarch Watch.