From Iowa to Mexico: The Monarch Migration

Each year, millions of monarch butterflies leave the northern US and travel thousands of miles to the forests of central Mexico, and here in Iowa, we have a front-row seat to this incredible migration.

Jacklyn Wolken, Conservation Technician

The end of summer in southern Iowa brings a sense of wonder, with thousands of monarch butterflies passing through on their journey to Mexico. At Des Moines County Conservation, one of our favorite activities is helping track their travels through monarch tagging. Each year, we catch and tag around 150-200 monarchs.

Every fall, millions of monarchs leave the northern US and begin their migration to the oyamel fir forests of Mexico. Here in southern Iowa, we usually see migrating monarchs arriving in the second half of August, drifting through prairie habitats rich with blooming wildflowers like New England aster, saw-toothed sunflower, boneset, goldenrod, and purple coneflower.

How Do You Tag Such a Small Creature?

The first step is to catch one! Patience and a little sneakiness are required since monarchs have sharp eyesight. Once a butterfly is caught, we record key details:

Where and when it was tagged
Whether it was raised in the wild or reared
Its gender
The unique tag number assigned

Then comes the tag itself; a small, lightweight sticker with a unique code. The tag is carefully placed on the discal cell, a mitten-shaped area of the wing close to the body. This spot ensures the butterfly isn’t unbalanced and hardly notices the tag at all. Once tagged, the monarch is released to continue its incredible journey.

Why Tag at All?

The process may sound simple, but each tiny tag carries big importance. By tagging monarchs, scientists uncover vital information about migration and survival. Each tag helps answer big questions, such as:

Where the monarchs in Mexico come from
What the timing and pace of their migration looks like
How many survive the long journey south

Together, these discoveries give scientists a clearer picture of what monarchs need to thrive and help guide efforts to protect them for generations to come. In fact, two monarchs tagged here in Des Moines County were recovered in Mexico several years ago.

Why Don’t We Tag Earlier in the Summer?

Not all monarchs are built for migration. Most monarch butterflies seen in Iowa from March through mid-August live only 3–5 weeks. Their main purpose is to move north, lay eggs, and then die, passing the torch to the next generation.

By late August, however, a special “super generation” emerges. Unlike their short-lived parents, these monarchs can live for up to nine months. They are the ones that make the epic flight to Mexico, overwinter in the mountain forests, and begin the journey north again in spring.

Here’s how the cycle works:

The super generation begins migrating south in late summer and spends the winter in Mexico.
In early spring, they head north, reaching the southern U.S. where they lay eggs and die.
The next generation hatches, goes through metamorphosis, and flies further north, where they lay eggs and die. These butterflies live about 3–5 weeks.
This cycle repeats for 3–4 generations, moving further north each time.
By late summer, the new super generation emerges, and the cycle begins again.

Migration is guided by seasonal cues, shorter days and cooler temperatures signal to the super generation that it’s time to start flying south.

How You Can Join In

We’d love for you to experience monarch tagging firsthand!

All About Monarchs Program – September 14 at 11:00 a.m. at Big Hollow’s Hickory Shelter. At this free program, participants will learn about the monarch life cycle, migration, and tagging efforts, and even try catching and tagging a butterfly. Please wear long pants, closed-toe shoes, and be prepared to stomp through the prairie.
Ladies Adventure Group Monarch Tagging – September 16 at 9:30 a.m. at Huron Flats. Open to women 18 and older, this program offers the same hands-on experience as the All About Monarchs program in a supportive, women-led group. This is a free event but RSVP is required.

You can also stop by Starr’s Cave Nature Center to see monarch eggs and caterpillars we’re raising. Once they emerge from their chrysalises, we tag and release them too!

How You Can Help Monarchs

Even small steps make a big difference:

Plant milkweed! This is the only plant monarchs lay eggs on, and caterpillars eat.
Grow pollinator-friendly flowers like goldenrod, joe pye weed, boneset, saw-toothed sunflower, and asters, especially those blooming late summer through fall. These plants provide nectar to fuel their long journey.
Avoid using pesticides and herbicides that harm butterflies, other pollinators, and the plants they depend on.
Join citizen science projects by tagging monarchs or reporting recovered tags.
Learn and share resources from groups like Monarch Watch and Journey North.

Monarchs connect Iowa prairies to Mexico’s mountains in one of the greatest migrations on Earth. By tagging, planting, or even just learning, you’re helping keep that journey alive. We hope to see you at the All About Monarchs program this September!

published Tuesday, August 26, 2025