As autumn arrives, an amazing natural wonder has been taking place in our backyards. Minnesota’s State Butterfly, the monarch butterfly, has begun its long annual journey south to its winter home. The same individuals you see here in late August and September fly all the way to a small area of forested mountains in south-central Mexico. Monarchs from across eastern North America huddle together by the millions, and acres of the Oyamel fir trees they roost on turn orange with monarchs. When spring arrives, they begin the return trip north, breeding as they go. This generation will make it back to about Texas next spring before their clocks run out, but their offspring will continue breeding and the journey north. By May, the grandchildren of the monarchs that are migrating south right now for the winter will make it back to Minnesota. Next autumn, the great great-grandchildren of this autumn’s generation will fly to Mexico to complete the cycle. A similar but smaller migration of monarchs occurs west of the Rockies to and from the California coast.
How do we know all of this? Much of what we know is actually thanks to people like you! A major “Citizen Science” initiative is to “tag” migrating monarchs in autumn with small stickers. Organized by Monarch Watch, a small sticker with a unique code is attached to the underside of one of the wings. The stickers are tough but very light and do not affect the monarch’s flight. Before being released, data is recorded about whether the monarch was wild or hand reared, male or female, and the location and date. Then, citizens in the US and in Mexico are encouraged (and even paid) to look for and report tagged monarchs. Recoveries allow us to learn more about how monarchs migrate and assess population sizes. During spring and summer, you can report your monarch (and bird!) sightings to Journey North. The University of Minnesota also hosts the important Monarch Larva Monitoring Project which uses simple observations from citizens to study what factors affect the distribution, abundance, and survivorship of monarch caterpillars.
Sadly, monarch numbers have dropped more than 90% at the Mexican overwintering colonies in the last decade. The monarch migration is now considered an “Endangered Biological Phenomenon” by the International Union for Conservation of Nature. Loss of habitat and their caterpillar food plants (milkweeds) in Minnesota and the Upper Midwest, illegal logging in Mexico, and bad weather events have combined to hit the populations hard.
Beyond contributing to citizen science initiatives, you can help monarchs (and other butterflies and pollinators!) by planting milkweeds and other native wildflowers in your yard. For some plant suggestions (35 species and growing!), check out our Plant For Pollinators page. The Monarch Joint Venture has a lot of additional information on ways you can help monarchs, as well. In the meantime, keep an eye out for tagged Monarchs! Minnesota Zoo staff tagged dozens of monarchs in recent weeks, and we wish them well on their journey to Mexico!