A Chance to Play Tag With a Royal Airborne Brigade

Tagging the monarch butterfly during its winter sojourn in Southern California may seem an exotic task, but Walt Sakai, biology professor at Santa Monica College, says he can train amateurs in an evening. And he does, once a year, in preparation for a field trip arranged through the L.A. County Museum of Natural History, where he is also a research associate.

On the recent trip to Goleta, his students gently caught and tagged about 2,000 of the small and exquisite creatures, each about half a gram in weight with a wingspan of up to 4 inches. Monarchs, which have a life span ranging from six weeks to eight months, are distinguished by their bright orange-yellow wings, bordered in a black flecked with white. While holding the monarchs still, the students used their fingernails to carefully rub off a section of scales on the forewing. Then they folded a small adhesive tag over the area. Printed on the tag was an ID number and toll-free phone number.

Months hence, when a tagged butterfly is recovered--usually because it is dead or dying--the finder is asked to call the monarch Program, based in San Diego, and provide the ID on the tab, as well as time and location of the find. This way, explains Sakai, “you can follow their migration. You can also use statistics and mathematics and estimate population size.” The ones seen on this field trip had made a trip from the Pacific Northwest, perhaps as far as southern Canada, to winter in California, alighting in fields and forests which provide their food--the nectar from the flowers of such plants as eucalyptus, lantana, and sunflower.

Their path here was a practical one. “They follow the path of least resistance,” Sakai says. They tend not to cross the Rockies because that would be too cold for them, so they zigzag down the Pacific coastline, some settling in California, some venturing as far south as Mexico. They can easily cover 1,500 miles on this journey.

The butterflies start arriving in mid-October and stay until late January to early February, at about 300 recorded sites from Mendocino to Baja California. They live in swarms from as little as a few hundred to as many as tens of thousands, pumping up the butterfly population in the region by upward of 2 million.