Monarch Larvae, Adult, and map of North America

Have you found this tag?

Monarch Alert Tag

Report your find toll free at

We place tags on the underside of monarch wings.  These tags allow us to individually identify butterflies that are later re-sighted.  Re-sighting information provides data on movement between overwintering sites, persistence at individual sites, population estimates per site, and migration patterns in spring.
If you locate a tagged monarch, please report the details about your sighting to Monarch Alert.

Interested in tagging Monarchs?
Send an email to request tags.

Download the Data Sheet

Download the Tagging Instructions



Help the Western Monarch

Did you know: Danaus plexippus, the monarch butterfly, overwinters in California and Mexico. During winter, California's monarch population can top 100,000. The exact numbers fluctuate from year to year. 

migrationProject Monarch Alert is a citizen-based research project backed by graduate student researchers and faculty from Cal Poly in San Luis Obispo.  We focus on the demography and population fluctuations of western monarch butterflies, through sampling of overwintering populations in San Luis Obispo and Monterey Counties.

The program rests on a solid foundation of research set by Dennis Frey, Ph.D., Emeritus Professor of Biology, Cal Poly, and by the Ventana Wildlife Society.  We appreciate all of their previous (and ongoing efforts) and acknowledge their essential contributions to this program.


Science on the SPOT: Monarch Meetup

Stu Weiss, Chief Scientist at the Creekside Center for Earth Observation, has been studying monarch butterflies for over two decades. Weiss uses a technique called hemispherical photography to analyze monarch butterfly overwintering habitat.  Read More ->

link to video on tree plantingPacific Grove Monarch Habitat Enhancement

In March, 2011, Cal Poly students, faculty and Monarch Alert researchers joined the City of Pacific Grove in planting trees in the city's Monarch Sanctuary. Watch the effort on YouTube

Button for link to Backyard Monarch Butterfly Garden Survey

Have a Butterfly Garden?

We Need Your Help!
Please complete our online survey about butterfly gardens and whether Monarch Butterflies breed in backyard gardens.

Support Monarch Alert

The Monarch Alert Project depends on private support from grants, foundations and citizen scientists like you.

Details on Giving to Monarch Alert
Give Online Now

Monarch Joint Venture

MonarchNet News, a citizen science newsletter produced by Monarch Joint Venture, will be published every other month and posted on the organization's website in the Resources section.

Prior Sponsor

Monarch Alert was funded by a generous donation from Pacific Grove, CA resident, Helen Johnson.

Read more about Helen ...

Helen Johnson