Master Gardener: Why Tag and Release Monarchs?

Imagine an insect that weighs less than a gram beginning a journey from Canada in late August and traveling over 2500 miles to spend the winter in the Sierra Madre Mountains in central Mexico. As daylight shortens in late summer, Monarch butterflies that were born near the Canadian border begin to migrate. This migration southward, and the northward return in spring, spans the life of more than four generations of the Monarch.

In the late 1930s Dr. Fred Urquhart, a zoologist at the University of Toronto began tracking Monarchs and experimented with tagging them to follow their movements. By 1952, he and his wife had developed a tag that would not fall off or impede the flight of the butterfly. That same year they founded the Insect Migration Association, and over the next 24 years they and thousands of volunteers tagged hundreds of thousands of Monarchs in Canada, the United States and Central America. Everything suggested that the millions of eastern Monarchs continued south of the border. But to where?

The question was answered by Kenneth Brugger, an American textile engineer living in Mexico, while out driving in the volcanic highlands west of Mexico City. In February 1973 he drove through a blizzard of orange and black butterflies, and wrote to Dr. Urquhart about the sighting. Urquhart received a research grant from National Geographic and hired Brugger to run down every rumor, follow every lead and visit every place where a tagged monarch had been captured. In January, 1975, near the town of Donato Guerra, west of Mexico City he found an estimated 15 million Monarchs on a slope of an inactive volcano in a forest of Montezuma pine, oyamel fir and cedar, on the edge of an alpine meadow. Within a year Brugger would find two other colonies, El Rosario, at 10,000 feet and Sierra Chincua at over 8,500 feet. In an August 1976 National Geographic article Urquhart wrote: “a branch, three inches thick, broke under its burden of languid butterflies and crashed to the earth, spilling its live cargo. One of them, by an incredible stroke of fortune, had been tagged.”

The tagger had been one Jim Gilbert in Chaska, Minnesota. Urquhart had his proof. Vanity Fair, “Dispatches from the Vanishing World”, November 1999

Why document this phenomenon? The primary reason is to promote the survival of the Monarch. It is threatened by habitat loss in North America and at the over-wintering sites in Mexico. Milkweed sources, the Monarch’s primary food, are declining due to development and widespread use of herbicides in croplands, pastures and roadsides. Many questions remain unanswered about the fall migration. How the Monarch manages to return to the same over-wintering spots, and how it navigates are still subjects for research. Do they move in specific directions, is the migration influenced by weather and are there yearly differences in migration patterns? Scientists and volunteers have been working to collect this data since the 1930’s to find answers to these questions. To help track population trends and migration routes, the University of Kansas established Monarch Watch, a Citizen Science program that uses volunteers to help capture and tag Monarchs.


The tag is 9 mm circle made of an all-weather polypropylene that has waterproof ink and a special adhesive that won’t hurt the butterfly. They are numbered for each tagging year with a toll-free phone number and an individual butterfly tagging number.

How do you tag a butterfly? The tag is placed over the large, mitten shaped cell, called the discal cell, on the underside of the hind wing of the monarch. This position is closer to the center of lift and gravity and will not impede flight or harm the butterfly.

After the butterfly is tagged, information including tag number, date, sex, and tagging location is recorded on data sheets and returned to Monarch Watch for analysis.


Males have an enlarged black pouch, called an alar, midway along the vein below the discal cell on each hind wing. Females have veins that appear thicker than the males but this may be due to a difference in pigmentation. You may notice that males and females differ in the anatomy at the tip of their abdomen. Females have a groove on the bottom side of their abdomen, while males don’t. The males have claspers arm-like extensions on the rear section of the abdomen used to clasp the female’s abdomen while mating. Females don’t have claspers.


Return the specimen with the tag, the tag itself or just the tag code to Monarch Watch. You should also include the location where you found the butterfly, date and circumstance of the recovery. The recovery data is posted on their website


We had more than 300 people turn out for our 2nd Annual Butterfly Festival and Fall Plant Sale with over 40 people to help with the Tag and Release Event. We captured and tagged 12 females and 12 males and sent them on their way to Mexico.

Here’s hoping they all made it safely!

Thank you to everyone that came out for the day whether it was for the plants or the butterflies. We were glad to see you all. We hope you will join us next year for the fall festival/plant sale again and look forward to seeing you in March at our 2012 spring plant sale.

October 27, 2011 – The first monarchs have reached their winter home in Mexico.

FYI: The Walker County Extension Office is now on Facebook!

WalkerCoTxAgriLife has been established to provide updates and information to Walker County residents and landowners on a timely basis. For more information on the Walker County Master Gardeners, please call (936) 435-2426 or visit our new website The WCMG website is a bounty of useful gardening information and citizens are encouraged to check it often.

If you have any questions about the information in this article or any of the Extension programs, please contact the Walker County AgriLife Extension Office at (936)435-2426, or Extension programs serve people of all ages regardless of socioeconomic level, race, color, sex, religion, disability or national origin. The Texas A&M University System, U.S. Department of Agriculture, and the County Commissioners Courts of Texas cooperating. A member of the Texas A&M University System and its statewide agriculture program.


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