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5 Monarch Migration Facts

By Isis Howard and Kailee Slusser on 10. October 2023
Isis Howard and Kailee Slusser

Every year as it gets colder, North American monarch butterflies migrate south between August and October. Monarchs that spend the summer breeding west of the Rocky Mountains tend to migrate to California coasts, while monarchs breeding further east migrate to Mexico. The butterflies cluster together in large groups at their overwintering sites to survive the winter. Once spring begins, these butterflies migrate north to start the breeding season all over again. 

 

Map of migration patterns of the monarch butterfly in North America
This map shows the migration patterns of the monarch butterfly in North America. The area covered includes Mexico, the lower 48 states of the US, and southern Canada. Overwintering zones occur on the mid and lower west coastline of California and in a concentrated area in central Mexico. Arrows extend away from these areas to show spring migration, mostly east from the California coast and north from Mexico. From Texas east to the east coast and from Kansas south to central Mexico is generally spring breeding habitat. Southern Florida is an exception, where resident, or nonmigratory, populations live all year. Areas in west Texas, southern New Mexico, southern Arizona, Nevada, California, eastern Oregon, and eastern Washington are breeding habitat in both spring and summer. Moving east from there all the way to the east coast and north into Canada as far as Lake Winnipeg, these regions are summer breeding habitat. From these summer breeding regions, arrows extend back toward overwintering zones to indicate fall migration paths, generally moving south and west toward Mexico and California. Western Mexico contains potential but unconfirmed breeding habitat. The northern limit of milkweed prevents monarchs from breeding in many parts of the US Pacific Northwest and most of Canada. Migratory monarchs also do not breed in Baja California or in southern Mexico below overwintering zones.

 

1. It's a long journey for a small insect.

A migrating monarch can fly up to 2,500 or sometimes even 3,000 total miles before reaching its destination. A monarch can travel over 100 miles in a single day with the right conditions. These butterflies coast on air currents to move quickly and conserve energy. They often fly at elevations where we can’t even see them from the ground, at 800 to 1,200 feet high. 

 

Two monarchs flying high in the sky
Monarchs weigh less than a gram and have a wingspan of less than 4 inches. Nevertheless, they can endure international flights! (Photo: Isis Howard / Xerces Society.)

 

2. It's every monarch's first and only migration. 

Monarchs that migrate north in spring will breed and pass away far before their descendents are ready to migrate south again. None of the monarchs on the fall migration path have ever been to their destination before, and yet they know exactly where to go. Scientists believe they use cues like magnetism and sunlight to navigate directionally, but the rest is still a mystery. 

 

Hundreds of monarchs in flight
Monarchs have an amazing ability to locate the exact overwintering groves that their ancestors used, despite never having been there themselves. (Photo: Candace Fallon / Xerces Society.)

 

3. Migrating monarchs live longer than others. 

The monarchs that migrate south are the last generation born each year, and they live up to 8 months longer than their ancestors from earlier in the summer. A typical monarch life span is 2 to 6 weeks. Migrating monarchs live up to 9 months, with their lifetimes spent migrating south, sticking out the winter, migrating north again, and finally breeding in the spring. 

 

Cluster of hundreds of monarchs on a tree branch
Several months of long flights and perilous winter is a long and hard lifespan for a butterfly that would have lived just a few weeks if born earlier in the summer. (Photo: Isis Howard / Xerces Society.)

 

4. Some monarchs don't migrate. 

Monarchs are famous for their migration, but some groups don't make the journey. For example, monarchs living and breeding in southern Florida and on other continents are able to sustain life year round without migrating. Scientists aren't certain if these resident monarchs don't migrate because of mild winters, a genetic difference, or a combination of factors. 

 

Monarch on swamp milkweed blooms
Most monarchs in North America are migratory, but in other places around the world, they stay local all year long. (Photo: Stephanie McKnight / Xerces Society.)

 

5. A lot of what we know came from community science. 

We have volunteers to thank for most of the available data about monarch migrations. For decades, community scientists have been collecting data by tracking, counting, and photographing monarchs on the move and overwintering. It’s how we know that monarch populations have declined dramatically since the 1980s. 

The Xerces Society facilitates and supports several community science projects throughout the year to continue researching these animals. Anyone can get involved! 

 

Several people looking up into trees with binoculars
Community science is a form of research that invites everyone—with or without a scientific background—to participate in generating data to further understanding. This methodology harnesses the power of numbers, often enabling larger data sets over a wider geographic range in a shorter amount of time. (Photo: Isis Howard / Xerces Society.)

 

Western Monarch Count

The Western Monarch Count invites community scientists near the west coast to count western monarchs at their overwintering sites from November to January. Volunteers count the overwintering butterflies around Thanksgiving and New Year’s, which helps us understand how many butterflies migrated to the coast in the fall, how many survived the worst of the winter, and how many are likely to migrate away from the coast in spring. Winter is an optimal time to count migrating monarchs, since it is the only time of year when they are clustered together in small and specific geographic regions. 

Learn More About the Western Monarch Count

 

Western Monarch Mystery Challenge

The Western Monarch Mystery Challenge is a community science project running from February to April, when monarchs start to migrate away from overwintering sites. The goal is to fill gaps in knowledge about western monarch migrations from coastal overwintering sites to summer breeding sites. 

Learn More About the Western Monarch Mystery Challenge 

 

International Monarch Monitoring Blitz

The International Monarch Monitoring Blitz invites community scientists in the United States, Canada, and Mexico to gather data about monarchs (both eastern and western) after they have migrated into their breeding grounds for the summer, in July and August. Resulting data helps us better understand the monarch butterfly’s breeding productivity, range, and timing in North America, which also allows us to gauge monarch quantities between migrations. 

Learn More About the International Monarch Monitoring Blitz

 

Western Monarch Milkweed Mapper

The Western Monarch Milkweed Mapper is an ongoing community science project to map milkweed and monarchs in all life stages in the western United States. Western monarchs are more vulnerable than eastern monarchs. Research from this project helps us understand how and where we can better support western monarchs in their breeding grounds, so that enough butterflies can successfully migrate in fall and survive through winters.

Learn More About the Western Monarch Milkweed Mapper

 

Monarch Nectar Plant Database

The Monarch Nectar Plant Database is a collection of community science observations from any time of year about which plants monarch butterflies nectar from. The data is ranked and used to give more accurate recommendations for planting nectar plants specifically to attract and feed monarchs. This project is not directly dedicated to migration research, but monarch plant preferences are very relevant for migration paths, on which monarchs need to stop for fuel often. 

Learn More About the Monarch Nectar Plant Database

 

Authors

As an endangered species conservation biologist, Isis works in California to protect and support the western population of monarch butterflies. She manages several community science projects, including the annual Western Monarch Count and the Western Monarch Milkweed Mapper, and provides support to land managers and the public on maintaining and restoring western monarch breeding habitat.

Kailee joined Xerces from Ohio in the summer of 2022, after several years working in marketing and communications for small businesses, nonprofits, and a university. She holds degrees in visual communications management and graphic design, while her other strengths include interactive user experience and audience research.

Kailee was drawn to Xerces because her dream job has always been to amplify environmental and wildlife protection through her creative skills. Her role includes work on the website, social media channels, and various designs.

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