Milkweed Sanctuary

Jeanne Filler Scott

Of all the world’s butterflies, only the monarch makes a two-way migration as birds do. Unlike other species of butterflies, monarchs cannot survive the cold winters in northern climates. The monarch knows when it is time to travel south for the winter, flying as far as 3,000 miles to reach their winter destination in the forests of central Mexico.

On our land in Kentucky, we have large patches of milkweed growing undisturbed for the monarchs and other creatures that depend on these plants. This includes other species of butterflies and moths, such as the milkweed tussock caterpillar or milkweed tiger moth. The monarchs and other insects that feed on milkweed leaves have evolved to tolerate the sticky white sap, which contains toxic chemicals to deter mammals and most insects from eating them. Other insects that rely on this plant, such as milkweed bugs and red milkweed beetles, use the toxins for defense. However, the flowers of the milkweed plant do not contain toxic chemicals, so bees, flies, and butterflies can safely feed upon the nectar.

Most monarch butterflies live for two to six weeks, but the generation of monarchs that migrates lives for six to nine months. This is because the last generation of the year does not become sexually mature as adults. They can live longer than the other generations because they overwinter in a cool location, which slows their metabolism. The butterflies cluster on trees for the winter, each tree hosting thousands of individual butterflies, which cover the branches and trunks. In the spring, they become mature, mate, and lay eggs as they migrate north, starting the first new generation of the year.

The monarch butterfly population has declined by 90 percent since the 1990s. The causes of the decline include habitat loss from intensive agriculture and urban development, and the use of pesticides and herbicides which kill milkweed, as well as other flowering plants that adult butterflies feed on. Climate change is another factor, as altered weather affects the patterns and timing of migration.