Why Tag a Monarch Butterfly

S urprisingly, tagging butterflies isn’t new! Tagging monarchs began in the early 1949’s to help learn the destination of monarch butterflies on their fall migration. Dr. Fred Urquhart developed a method to tag a monarch using paper tags that were glued over the leading edge of the upper wing. Today with newer technology available, tags are now lightweight and waterproof and can be placed in the dorsal (under) side of the discal cell, a mitten shaped cell in the monarch’s lower wing. When placed properly in the discal cell and then pressed lightly for several seconds afterwards, the heat and pressure force the adhesive on the back of the tag through the scales where it becomes securely attached to the butterfly’s wing. 

The big advantage of using the newer tags is they don’t interfere as much with the monarch’s flight when attached properly. If someone is lucky enough to spot a tagged monarch enroute or at their destination we can all learn where monarchs migrate each fall.

We now know that monarchs migrating through Arizona (or from Arizona) spend the winter in California or Mexico; some spend the winter in the lower deserts of Arizona and California as well. With monarch population numbers plummeting in the West, understanding more about their key migration routes is essential to enhancing viable habitat along their journey, benefitting both monarchs and other pollinators. But tagging data isn’t limited only to learning more about the migration destination. Data gathered as part of the tagging process has provided other key information as well. 

At the time of tagging, monarch gender and activity when they are captured is recorded. Most monarchs are found nectaring on flowers and as a result we’ve been able to create a key nectar resource list to aid in restoration projects in the Southwest. Taggers are also asked to rate the condition of a monarch’s wings. Are they fresh and new looking or are scales missing or wing pieces missing or damaged? Through over 74 recoveries of monarchs sighted in Mexico or California we now know that primarily monarchs with bright colored and new looking wings without blemishes at the time of tagging are most successful in migrating. More male monarchs are tagged than female monarchs, a common finding in tagging programs. This is because males are generally more active and their higher metabolism requires them to feed more. Most monarchs are tagged in the mornings or late afternoons because this is when they are most present in the field.

The Southwest Monarch Study looks at the data collected upon tagging: date, condition and tagging location. From this, we determine the sun angle, the elevation angle of the sun at its highest point (solar noon). We have learned that the sun angle determines when a monarch develops the urge to fly south. The angles are monitored for patterns over time. Through tagging and the recovery of tagged monarchs in California or Mexico, the Southwest Monarch Study has been able to determine the Peak Migration time for the Southwest states. The peak migration window alerts everyone interested in tagging to tag monarchs extensively for the best opportunity for a successful journey to the overwintering sites. 

Dr. Chip Tayler et al recently published a paper indicating a similar finding through his Monarch Watch tagging program. While it is unknown if it is the actual sun angle or something occurring at the same time, there is a distinct pattern to the monarch butterfly’s successful migration through a region. Outside of these key times, recoveries at the overwintering sites drop significantly. 

Yes, monarchs will fly through before and after these dates and in some years, there may be a weather-related delay in their arrival, but the most successful flights to the overwintering sites will occur during this time frame.

It’s easy to focus on what we’ve learned about the migration destination through tagging in Arizona. But new tagging data about monarchs that do not migrate but spend the winter in the lower deserts is also painting a new picture of the monarch’s survival resiliency. Monarchs lose the urge to migrate in late November or early December when the sun angle decreases considerably from day to day. With warming temperatures in Fall, it is possible late monarchs arrive in the lower deserts or eclose from a chrysalis during this time frame and so lack the urge to continue to migrate. 

Monarchs tagged during November and December in the greater Phoenix, Tucson, Parker and Lake Havasu areas often are seen still flying through the winter months. Breeding monarchs normally only live for two to six weeks but nonbreeding monarchs can live up to nine months. Seeing winter tagged monarchs alive and active the same locale three months after tagging indicates they are likely non-breeding monarchs. In his early studies in Arizona, Dr. Fred Urquhart reported both breeding and nonbreeding monarchs in the deserts of Arizona so this finding is not unique or surprising. Through tagging during winter, the Southwest Monarch Study Community Scientists are able to document a monarch’s longevity and activity during this time now as well.

Join us on Sunday, September 19 or Saturday, September 25, and become a Community Scientist to tag monarchs at Bubbling Ponds in Cornville! We ask you preregister at info@swmonarchs.org as each event is limited to 15 participants. We’ll provide the nets and data collection sheets and guide you through a fun morning of learning more about the amazing monarch butterfly during their Peak Migration. How to tag? Visit https://swmonarchs.org/upcoming-events.php for more information and what to bring. Jump ahead and watch videos about tagging at this informational link:  https://swmonarchs.org/tagging.php

Gail Morris

Southwest Monarch Study Coordinator