Tagging Monarch Butterflies

Each fall Monarch Watch distributes more than a quarter of a million tags to thousands of volunteers across North America who tag Monarchs as they migrate through their respective areas. These “citizen scientists” capture monarchs throughout the migration season, record the tag code, tag date, gender of the butterfly, and geographic location, then tag and release them. At the end of the tagging season, these data are submitted to Monarch Watch and added to their database to be used in research.

Carol Pasternak, The MonarchButterfly Crusader, is catching monarchs in Ontario in order to tag them.

Tags are tiny, lightweight, round stickers. They are a little larger than a hole-punch, about 9 mm in diameter. Each tag has a unique ID number. When a tag is recovered (found again), valuable information about migration is revealed.

The tag is placed on the underside of the hindwing of the Monarch. This tagging method places the tag close to the center of lift and gravity for the butterfly so as to not interfere with flight or otherwise harm the butterfly.

According to Monarch Joint Adventure, “The purpose of tagging Monarchs is to associate the location of original capture with the point of recovery for each butterfly. The data from these recaptures are used to determine the pathways taken by migrating Monarchs, the influence of weather on the migration, the survival rate of the Monarchs.

Tagging kits are available via the Monarch Watch Shop.

Coded tags are attached to Monarchs when they are captured before or during their southbound migration, and recovered when Monarchs are found throughout the migration or overwintering season. Citizen scientists record the date, location, Monarch gender, and unique tag number for each fall-migrating monarch that they tag and then submit these data to be used in research. The tags and tagging process do not harm the butterflies, and the data collected have the potential to answer many important questions about monarch biology and conservation.”

Tagging helps answer questions about the origins of Monarchs that reach Mexico, the timing and pace of the migration, mortality during the migration, and changes in geographic distribution. For example, by tagging Monarchs and collecting data, we have learned that these butterflies can travel at least 170 miles in a single day and that they have traveled as far as 3,000 miles. In fact, tagging led to the discovery of the monarch’s winter home in Mexico. (Read more of this fascinating story here.)

Monarchs can travel between 50-100 miles a day; it can take up to two months to complete their journey. The farthest ranging Monarch butterfly recorded traveled 265 miles in one day.

Monarch Watch, the Southwest Monarch Study, and Monarch Alert all have monarch tagging programs and are always looking for more citizen scientists; find the program that’s best for you and get involved!

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Follow the Monarch Migration

It is that time of year when Monarch butterflies are starting their long migration south to Mexico. During the next three months, millions of Monarchs will travel 2500-3000 miles across Canada and the United States headed for warmer weather in Mexico.

During their migration Monarch butterflies need to stop and refuel on flowers.

The Monarchs (Danaus plexippus) fly during the day, typically traveling alone. They do not migrate in flocks like many birds. But in the early evening, they will rest in trees. Sometimes they cluster in small groups, and sometimes they form large clusters. These clusters of Monarchs are called roosts. Most roosts last for only a night or two but sometimes these gatherings may last as long as two weeks.

Linda Cresswell took this photo in Ajax, Ontario, Canada, where she observed hundreds of Monarchs in the wildflower meadow and roosting in the oak trees. (Photo Copyright © 2020 Linda Cresswell. Used with permission.)

Why do monarchs roost? According to Journey North, “One hypothesis is that roosting behavior is an anti-predator strategy. Cool temperatures paralyze monarchs, making them vulnerable to predators. A roost provides safety in numbers. When overnight temperatures are warm, monarchs may not aggregate as tightly or roost at all. Perhaps monarchs shift to roosting behavior when cold overnight temperatures make them vulnerable.”

A small group of Monarch butterflies gathers together to rest and to protect themselves at night.

Where do Monarchs roost? Roosts are more likely found in certain habitats but are not consistently found in the same place. They vary from year to year. Roosts can often be found near nectar sources, in trees that are downwind, and near a major flyway. Flyways are typically near valley streams or depressions that provide a cool moist environment. (https://journeynorth.org/tm/monarch/FallRoosts.html)

Monarchs cluster at La Huasteca, Santa Catarina, Nuevo León, Mexico. (Photo Copyright © 2020 Omar Franco Reyes. Used with permission.)

One of the best ways to follow the fall migration is to track where they are forming roosts. Journey North keeps and posts data collected by citizen scientists on where roosts are being observed. The roost map shows where there are large concentrations of monarchs. Week by week, it reveals the fall migration pathways to Mexico and the pace of the migration.

The northern migration is tracked by an organization called Journey North. You can help track the migration of the monarch butterfly by visiting this site.
The Monarch: Saving Our Most-Loved Butterfly by Kylee Baumle