By David G. James

Since 2012, I have had the pleasure of working with citizen scientists to conduct a monarch tagging program in the Pacific Northwest to determine where our relatively small population migrates to every fall. It was long suspected they overwintered along the California coast but the evidence for this was confined to a single butterfly tagged by Bob Pyle on the Washington side of the Columbia River Gorge that was later found in Santa Cruz, California. Since 2012, we have tagged 31,153 monarchs in Washington and Oregon and recovered 219, most of them in California, a recovery rate of 0.71%. Most of the details of the tagging and recoveries made by our program are presented in two papers (James et al. 2018, James & Kappen 2021).

However, while we are now confident that all monarchs in Oregon migrate to California in the fall, and about 98% of Washington monarchs do the same, we are still uncertain as to where most Idaho monarchs migrate to. Since 2012, we have tagged 11,096 monarchs in Idaho but have only recovered 12 (0.11%). Of these, only 2 were found in California (0.02%), with most of the remainder found in Idaho south of release points at distances of up to 100 miles. In James & Kappen (2021), we conjectured that most migrating monarchs from Idaho move south to south-east ending up in Arizona or Mexico. However, after 13 years of tagging monarchs in Idaho with sticky paper tags, we are no closer to solving this mystery…..until now.

For years monarch researchers have dreamed of being able to tag monarchs with a transmitting device by which we could follow the migration of individuals. If you think of monarch migration as being a book, then paper tags allow us to see the opening page and the final page, with what happens in-between, a mystery. Electronic tagging of individuals would allow a real-time insight into migration dynamics. I know I dreamed this dream 50 years ago when I tagged monarchs in Australia and spent hours hand-writing paper tags! Well, the magic day has arrived and viable electronic tagging of monarch butterflies is a reality!

Cellular Tracking Technologies (CTT) (https://celltracktech.com/) based in New Jersey, began working in 2015 on BluMorpho, a tiny solar-powered transmitter light enough for a monarch to carry. Within a decade, they achieved this goal. The other game-changing advance was making every device that is Bluetooth-enabled into a BluMorpho receiver. Thus, every Bluetooth-enabled smartphone is a data receiver for any BluMorpho-tagged monarch within a quarter of a mile. In the fall of 2025, BluMorpho transmitters, weighing 60 mg each, were attached to 400 monarchs and released at locations from Canada to Cuba. Very excited and amazed monarch researchers and enthusiasts watched spellbound as routes of individual monarchs appeared daily on their cell phones via the Project Monarch app. Some BluMorpho-tagged monarchs released in Canada reached the Mexican overwintering sites in November, proving that they could fly all the way to Mexico with their 60mg tag. Independently, a study looking at the impact of electronic tags twice the weight of BluMorpho tags on different butterfly species, concluded that tags below 20% of butterfly body weight are unlikely to affect flight performance (Heitzler et al. 2025). BluMorpho tags weigh < 10% of the weight of a migrating monarch.

Can BluMorpho help us solve the Idaho monarch mystery? I think the answer must be a resounding yes! Only one problem remains. Currently, BluMorpho tags cost $200 each and while we don’t need thousands of tags as we did for paper tags (witness the data achieved from 400 BluMorpho-tagged monarchs in the eastern US during fall-winter 2025 https://celltracktech.com/pages/project-monarch-collaboration-2025), it would be prudent to have at least 100 to gain enough data to at least begin solving the mystery.

Enter Patrick Adair and his monarch conservation organization Wings Rising (https://www.wingsrising.org/) and a plan we hatched to Adopt-A-Monarch! If you want to help us solve the Idaho monarch mystery you can adopt a monarch and name it by donating $200. You will also get the excitement of being able to track your monarch on your cell phone! Just go to http://adoptamonarch.org and follow instructions. With the help of BluMorpho tracking technology and generous monarch advocates, we WILL solve this last remaining mystery of Pacific Northwest monarch migration!

Literature Cited

James, D. G., James, T. S., Seymour, L., Kappen, L., Russell, T., Harryman, B. & Bly, C. 2018. Citizen scientist tagging reveals destinations of migrating monarch butterflies, Danaus plexippus (L.) from the Pacific Northwest. Journal of the Lepidopterists Society, 72: 127-144.

James, D. G. & Kappen, L. 2021. Further insights on the migration biology of monarch butterflies, Danaus plexippus (Lepidoptera: Nymphalidae) from the Pacific Northwest. Insects, 12: 161.

Heitzler, S., Dallmoller, S., Hinneberg, H., Murillo-Hiller, L. R., & Gottschalk, T. K. 2025. Radio telemetry of butterflies: Practical insights and critical tag-weight thresholds. Movement Ecology, 13: 86.