October 4, 2006--Milkweed Rest Stops

First there was an unexpected, out-of-context hummingbird visiting our terrace, then a few weeks ago while heading east on 9th Street in search of the perfect sushi bar, fluttering its way among the blossoms in a street-side flower box was a glorious Monarch Butterfly. I didn’t know at the time that it was sucking in a last taste of nectar before taking off on a 3,000 mile trip to its winter mating grounds in northwestern Mexico.

It was about to join millions and millions of other Monarchs on their annual migration. A migration that takes them from Canada to Mexico and then part way back. They get all this accomplished during just the brief six to nine months that they live. (See NY Times article linked below.)

That winter home in Mexico consists, amazingly, of only 14 acres. Talk about threading the navigation needle. And they find their way back and forth without anything approaching a brain the size of migratory birds.

How do they get the job done? What secrets are hidden in the rudimentary ganglia that constitute all the neurological capacity they have to funnel their way to Texas, between the ridges of Mexico’s Transvolcanic Mountains, and then locate that tiny grove?

Though we have pretty good knowledge about the inner workings of the atom and the “creation” of the universe, though we may have landed men on the moon and perfected Smart Bombs, about how the Monarch Butterflies do their thing, though this has been and continues to be carefully studied, we as yet do not know. It remains one of nature’s enduring mysteries.

Theories abound—some say they have the olfactory capacity to smell the remains of Monarchs that died along the way the previous year—sort of a charnel pathway—but that is controversial since butterfly bodies do not contain the “odiferous fatty acids” that would be required for the smell of their dead bodies, sorry, to last a year.

Others claim that they find their way like birds, orienting themselves by observing the stars, by utilizing the earth’s magnetic field, or by following familiar landmarks on the ground; but this too is disputed since they do not have, as you know, the brains of birds.

So it must be that they are guided by sunlight, by the direction of the sun as it moves through the angles of the seasons. This is the best theory thus far since Monarchs appear to set out on their migration when the sun in their latitude drops to about 57 degrees above the southern horizon.

One thing though is clear, with just those very few neurons, well before homo sapiens (us) in the 1700’s developed the capacity to measure longitude, the lowly Monarch had that ability.

There is one very nice coda to this story—because of global warming (that is not the nice part) the season for wildflowers is shifting. This has dangerous implications for the Monarchs since as they travel, like the rest of us, they need to stop for nourishment—in their case by pausing to grab some milkweed. But since there is less and less milkweed around, friends of the Monarchs have recruited people along the flight path to plant milkweed patches. Thus far, more than 1,000 have—in private gardens, schoolyards, city parks, and even golf courses!