Monarch butterflies are large graceful orange and black striped butterflies that flit and float through summer gardens. They may be best known for laying their eggs on milkweed plants and the protection these plants provide for the caterpillars. As the host plant, the young caterpillars chew on the milkweed’s leaves and ingest the plant’s toxic compounds called cardiac glycosides. Stored in their bodies and wings, these chemicals make the creature toxic to predators.
The colorful bands on the caterpillar and adult’s coloration are signals to predators that these are foul tasting creatures. Some still are eaten, but the predator learns a valuable lesson as to unpalatable nature of these butterflies.
Predation is not a main stress on the monarchs, rather these beautiful butterflies face increasing impacts to their populations from habitat loss, agricultural practices and herbicides. Butterfly researchers have observed alarming declines of monarchs over the past 20 years; such precipitous drops that one of the greatest North American migrations is in jeopardy.
In the early 1990s, researchers estimated that over 1 billion monarchs migrated several thousand miles from the northern plains of Canada and the United States to the oyamel fir forests in the mountains north of Mexico City. In the forests, the monarchs would gather by the thousands, the trees decked with winged capes. Another million or so monarchs also migrated from the western edge of North America to locations in California. Monarch Watch, a butterfly conservation organization, produces a booklet describing 25 sites in San Diego, L.A., Monterey and elsewhere. In these warm winter climates, both in California and Mexico, the monarchs overwinter as adults.
In February, the monarchs starting feeding again and prepare to move northward. Adults mate before they leave; when the butterflies reach the southern U.S. they lay eggs and die. In spring, the eggs hatch and the caterpillars move through into the adult stage, and then continue into Canada and the northern U.S. These adults will migrate.
But agricultural practices in terms of herbicide use, habitat loss in both the U.S. and Mexico, and roadside mowing or spraying of milkweeds have drastically reduced the availability of host plants and nectar plants crucial during migration, but also during the caterpillar season. Since no monarch survives the entire round-trip migration – it is the next generation or the great-grandchildren generation that returns home – the survival of the caterpillars to adult stage is critical. The process of migration is an inherited trait in monarchs, since it is several generations later that return to the wintering grounds. How the butterflies know where to go is an amazing mystery of nature.
Though there are conservation organizations and government entities working towards preserving habitat and setting policies and coordinating efforts across 3 countries, there is an important role that backyard gardeners can play in this picture. It can be as simple as planting some milkweeds or nectar plants in the garden or creating a monarch pit stop.
Establishing monarch waystations, sort of like highway rest areas, can be a significant contribution towards protecting this species. Planting milkweeds native to the region is a way to provide host plants for the females to lay their eggs on. Including nectar plants suited for these butterflies for fall migration, especially asters and goldenrods, will provide important fuel for the migrating monarchs. The waystations don’t need to be huge, although fallow fields and roadside ditches shouldn’t be overlooked as good monarch habitat. A small garden plot or mixing these species within established gardens would help.
City parks and urban open spaces could also use some milkweed warriors to convince managers and planners of the importance of including these plants in their landscaping plans or to minimize the use of chemicals to control weedy plants that may be beneficial to monarchs. Sometimes the planting of a seed can be through a letter to the editor or note to local government and doesn’t require digging in the soil. I confess to a little guerrilla gardening by dropping milkweed seeds along irrigation ditches, abandoned fields and other areas where they are likely to thrive.
Last year on a return trip from the Southwest, I harvested ripe milkweed pods from various roadside ditches along some back roads. Though the air filled with white parachutes and I lost some seeds, I walked away with a bag full of pods. I planted some seeds to overwinter in the ground, and others I am germinating this spring. I plan to add these plants to my existing wildflower gardens that already attract mourning cloak, swallowtail and tortoiseshell butterflies. These gardens are full of late season rudbekia, coneflowers, asters and other nectar producing composites.
This year, I might even hang a sign proclaiming my waystation just in case the monarchs are looking for a rest stop during their long migration.