Following Monarchs to Mexico

You've been studying monarchs for 45 years. How did you come to focus your work on the monarch?

I began with an interest in whether or not the monarch was truly an unpalatable butterfly, as was assumed in the 19th- and 20th-century scientific literature. The historical hypothesis held that the monarch derives its unpalatable qualities from bitter substances in its larval foodplant (milkweed). When I tasted the "milk" of the Florida sandhill milkweed, I almost threw up.
 
Then, while a grad student at Yale University, the late Professor G. Evelyn Hutchinson asked me to present a lecture on monarch migration. I soon combined the two research thrusts and eventually determined that monarchs are indeed toxic to birds because of heart poisons that they sequester as larvae from the milkweeds.
 
I gained some notoriety, summed up on a T-shirt emblazoned "Brower's Barfing Blue Jays." My colleagues and I then determined that some milkweeds had no cardiac glycosides in them, and produced monarchs that were palatable to the jays. When Fred and Norah Urquhart published their 1976 article in National Geographic, they mentioned that birds were apparently eating many monarchs.

This set off a lightbulb in my brain and provided an opportunity to test our hypothesis in the natural environment. A post-doc colleague and I visited the Sierra Chincua colony in January 1977. We confirmed that grosbeaks and orioles were eating up to a million monarchs over the course of the winter. My students and I then determined that some monarchs are very toxic, others are of intermediate palatability, and others are completely palatable.
 
When I first visited the Sierra Chincua Sanctuary in Michoacan, my first sight of the vast numbers of monarchs festooning the oyamel firs on that magical mountain changed my life. I instantly recognized the fragility of the whole migratory phenomenon and have spent the rest of my career providing scientific justification for the conservation of these magnificent mountain hideouts for the millions of monarchs that migrate there each winter. The aesthetics and biology of the monarch phenomenon are as unique and wonderous as anything I have could possible imagined.

What's the effect of habitat endangerment on monarch migration and survival?

There are two major threats to the migration of the monarch, which we have termed "an endangered biological phenomenon." These are 1) the ongoing destruction of the oyamel forests in Mexico due to several kinds of illegal logging and 2) the widespread chemical GMO agriculture in the U.S. and Canada that is eliminating hundreds of thousands of acres of monarch breeding habitat.
 
Are the governments of the U.S. and Mexico working together to protect this amazing phenomenon?

There are some promising new programs involving the collaboration of Mexico, the U.S., and Canada but unless the logging is stopped, the overwintering habitat is properly protected, and some sort of compromise is reached on sterilizing the North American breeding habitat, I think the monarch migration may become doomed in the near future.
 
Where do you stay when you're in Mexico to study the monarchs' overwintering?

We stay in the town of Angangueo in the Hotel Don Bruno. Bring your longjohn PJs, nights are cold.
 
Do you have any travel tips/must sees for those going to Mexico to see the overwintering for themselves?

There are many fascinating sights in this part of Mexico. I recommend spending two or three days with the butterflies, followed by a visit to the culturally rich cities of Morelia and Pátzcuaro (about a two- to three-hour drive west of Angangueo). Both cities offer fabulous opportunities for history, good food, and shopping.

Photos: top, Annie Griffiths Belt; bottom, Perry Conway