Labels

Tuesday, October 5, 2010

The Return of the King

I knew something was up when I counted 20 big, orange and black butterflies crossing Route 9 in as long as it took to fill up the gas tank the other day. The number swelled into the hundreds as I made the 7-mile drive east on Hwy 40 to Old Fort. The monarchs were on the move, and they were, to a bug, heading south.
The fact that monarchs migrate in the fall, much like birds, is common knowledge among amateur naturalists. Through tagging studies, scientists have found that monarchs, which weigh less than a paper clip, can fly more than 200 miles a day with favorable wind. Other insects, green darner dragonflies for instance, also head south to escape the killing frosts of winter. Monarchs, however, are the most-easily recognized and beloved of the migratory arthropods. Everyone knows these showy bugs at a glance. They look like they're dressed for Halloween. And most kids with a slant toward being outside learn the life cycle of the monarch: The adult females lay eggs on milkweed, which serves as the food plant for the caterpillars. The caterpillars metabolize the toxins within the milkweed, becoming rather distasteful themselves to predators. The monarch chrysalis, or cocoon, is perhaps one of the most-elegant structures in nature - like emerald rain drops inlaid with gold. The adults emerge from the chrysalis and carry forth.
If you paid attention in your high school biology class, you might also recall the popular teaching example of Batesian mimicry, in which monarchs play a key role. While monarch butterflies are boldly patterned, presumably to pronounce their unpalatable flavor to predators, the slightly smaller and unrelated viceroy butterfly is quite delicious. Natural selection, however, has bestowed the viceroy with a color pattern so similar to monarchs, that they are able to avoid predation by mimicking their larger benifactors.
Yes, the scientific community has known about monarchs for quite some time, including their need to fly south in the fall, but the distance and ultimate destination of the annual exodus of the eastern population wasn't discovered until 1976. The great wintering encampment is relegated to just a handful of sites at over 10,000 feet above sea level in Mexico's Sierra Madre mountains. Within these protected oyamel fir forests, the micro-climate allows the butterflies to survive the winter in various states of torpor. Similarly, in the West, a smaller number of monarchs fly south in the fall and winter along the Pacific coast near Santa Cruz and San Diego. Recently, researchers have become alarmed by record low numbers of wintering monarchs at the traditional spots in the Sierra Madre. An unfortunate convergence of storm damage and illegal logging has reduced the suitable micro-climate to an area about the size of two football fields. There has been some discussion of the potential extinction of the eastern monarch migration.
Happily, those fears have been set aside, at least for the short term, with the astounding number of butterflies heading south this fall. Experts are pointing to the perfect breeding conditions in the East that the monarchs enjoyed this summer for the population explosion.

The hundreds monarchs I've been seen flying along the Blue Ridge over past three weeks are but a tiny portion of the massive migration that took place along the East Coast during September. Cape May, NJ, the most-venerated site to witness fall migration of both birds and butterflies in North America, experienced a monarch flight of epic proportions. At the peak (Sept. 19), Mark Garland, Cape May resident, butterfly and bird expert, author, and most-especially to me, an old friend, estimated the flight at over 1 million. He called it indescribable - and Mark's been doing monarch research for more than 20 years.
Here in western North Carolina, we didn't see anything like the spectacle shown in the video, but, if you were paying attention, you were a witness to one of the last great mass migrations left on Earth.
The Butterfly upon the Sky, by Emily Dickinson
The Butterfly upon the Sky,
That doesn't know its Name
And hasn't any tax to pay
And hasn't any Home
Is just as high as you and I,
And higher, I believe,
So soar away and never sigh
And that's the way to grieve --

3 comments:

  1. A few years ago I went on a weekend's birding on Portland Bill on the south coast of England, some time in October. Lots of our summer visitors heading south to the Med and Africa for the winter. The highlight was a Monarch butterfly, perhaps caught in a strong westerly wind, or maybe ship-assisted. It was amazing to think of such a frail creature making it across the Atlantic!

    Interesting blog!

    ReplyDelete
  2. One of the most interesting things about monarchs is the recent discovery that the last generation to emerge in mid to late summer has a distinctly different wing structure; longer, stronger and more suited to migration. Amazingly, they are regularly spotted along the eastern Atlantic when, as you suggest, some are blown across the sea by westerly winds.
    Thanks for the comment. Glad you like the blog.

    ReplyDelete