Monarch Butterfly Migration (Danaus plexippus)
With thanks to the National Park Service
Dependent on habitats in Canada, the United States, and Mexico, the monarch butterfly illustrates the need for international ecological cooperation and conservation.
The monarchs' migration spans generations. During the summer breeding season, monarchs live only 2-5 weeks. Each successive generation—and there may be as many as four within the breeding season—continues the northward journey. The last generation of the year migrates south to the oyamel fir forests of Mexico.
On their northward journey, the monarchs feed on the nectar of many flowers, but lay their eggs only on certain varieties of milkweed plants. Designated as noxious weeds in some areas, however, milkweeds are often eradicated.
The monarch's winter habitat in Mexico's fir forests is shrinking. Because all monarchs gather in only a few locations during the winter, the overall population is especially vulnerable to disruptions, deforestation, or harsh weather.
Traveling between 50–100 miles a day, the monarch's migratory journey may be 3,000 miles long and take two months to complete. The last generation of a breeding season must attempt the entire reverse journey back to Mexico. These tiny travelers weigh less than a gram and may live as long as nine months.
Monarch Butterfly Fall Migration Patterns. Credit: Base Map, USGS National Atlas, USFWS.