Dr. Lincoln Brower

Photo by Don Davis

Dr. Brower and Dan Slayback, his colleague who works at NASA as a Geographic Information System expert, headed down to Mexico on Thursday, 8 February. They're joining up with Lighthawk, an NGO that provides aerial flights over environmentally sensitive areas.

They're joining up with UNAM colleague, Isabel Ramirez, and are conducting extensive flights over the entire Monarch Butterfly Biosphere Reserve searching for monarch colonies. They have a manuscript in press with the Entomological Society of America that will be published in April that describes their findings of the past three years doing this aerial research.

"This year, we hope to be able to verify that monarchs are returning each year to form their colonies in almost the exact same areas that they have occupied each year dating back to 1975 when the first colony was discovered on Cerro Pelon," says Brower. "When we began our flights three years ago, we predicted that we would find overwintering colonies in many locations that seem to have the requisite geographic features:

• on large mountain massifs west of Mexico City
• on SW facing slopes
• at about 11,000 feet elevation,
• and in rich Oyamel fir forests.

Much to our surprise, we found no new colonies in flights that covered about 60% of the potential habitat. We hypothesize that the fall migrant monarchs are somehow marking the areas with some chemical that persists from the time they leave in March to the following November when their great grandchildren return. This year we will repeat our observations to see if they hold up.

"The big question is, why are they so limited when there seem to be many mountain valleys in which they could overwinter?

"The implications are astoundingly important: (1) if they are coming back to the same spots each year, how do the find them? And (2), since there are so few locations they use, protecting these precious areas from logging becomes more important than we could have imagined."