We’ve all heard about the great monarch migration. Millions of butterflies fly to Mexico or Southern California every fall, some traveling as far as 3000 miles to escape the winter cold, and millions fly back every spring. But what is not as well known is that no butterfly makes the complete round trip.
A female monarch may fly as far as the Gulf Coast in the spring, and lay eggs on a milkweed plant there. Caterpillars will emerge from the eggs, feed on the milkweed, and pupate. It is the new butterflies that will continue the northward journey, following the emergence of milkweed throughout the summer. Meanwhile, the original female has died. Several generations are born each summer, and it is only the monarchs of the last generation that migrate south in the fall.
The monarch is fairly well protected from natural predators because of a toxin it ingests as a caterpillar when it feeds on milkweed. But it is defenseless against the changes in both its summer breeding grounds and its overwintering sites. Native milkweed, mandatory for the butterfly’s survival, is declining throughout North America, due to drought in some places and development and changing agricultural practices elsewhere. Development is also replacing the trees where monarchs winter in California. And deforestation in Mexico threatens the populations that winter there.
Efforts to protect the monarch migration will need to happen at every segment of their journey, both north and south. Follow the links at earthwiseradio.org to learn more about ongoing conservation efforts and about citizen science projects for tracking monarchs.
Web Links
Monarch Joint Venture
http://www.monarchjointventure.org/Default.aspx
Xerxes Society Monarch Information Page
http://www.xerces.org/monarchs/
U.S. Forest Service Monarch Larva Monitoring Project
http://www.fs.fed.us/wildflowers/pollinators/monarchbutterfly/citizenscience/index.shtml
Photo, taken on November 5, 2012, courtesy of William Warby via Flickr.