Small Brains and Large Distances

monarchs-sky-370_11892_1We’re home after checking out the monarch butterfly wintering area in the mountains of central Mexico. It may sound silly – visiting a butterfly sanctuary, but it’s a special event that could be wiped out one day by environmental pressures.

We visited the butterfly sanctuary on a Monday and were the only people there besides our guide and a sanctuary guard. It is a little hard to get to, it’s a two plus mile hike up to around 10,000 feet, which deters visitor traffic.

Once you’re there you’ll find a few areas about 75 feet square in which most of the pine trees have branches that seem to be sagging because the butterflies are so densely huddled in to regulate their exposure to the cold. The butterfly laden branches look more like giant thick dreadlocks than pine tree branches. There were millions of butterflies there and it’s hard to imagine the scene not long ago when there were sometimes around a billion butterflies in the migration.

The sanctuary areas are cool in the day but when the sun comes out the butterflies  begin sort of vibrating to warm up before taking to the sky in numbers you can’t imagine. It’s magical, surrounded around and above by so many butterflies flying that their thousands of beating wings make enough noise to hear.

In the Spring, the butterflies head north from Mexico to the Gulf coast of the US where they reproduce and die. The offspring then continue north. The slow trip North goes on until the  fourth generation (the great-grand kids) images it to Canada. Then, somehow, late in the Fall a long trip back to the small remote area in the mountains of central Mexico starts. Their journey is the longest migration in the insect world.

Scientists don’t know how an insect with a small brain navigates such a large distance, to a special spot in Mexico the butterfly has never been to, because no individual butterfly makes a complete round trip! Their great grandparents made the trip the year before but they died after reproducing on the Gulf coast after leaving Mexico. The how and why of the migration is still a mystery.

Many things are working against the monarch butterflies’ annual migration. Most of the flowers important to the monarchs, especially milkweed, are weeds people try to control with herbicides. And there’s occasional illegal logging within their Mexican sanctuaries disturbing the delicate temperature regulation there, making the butterflies susceptible to freezing to death. Increasing urbanization and farming along their path can cause problems. Plus being better at gliding and soaring, than flying by flapping their wings, makes butterflies need the right weather for flying, they just aren’t very efficient flyers.

Researchers didn’t even know where the monarch butterflies were migrating to until the 1970’s. With luck and the awareness of people, the Monarchs will be able to continue their amazing migration for as long as possible.