by Guest Blogger Kevin H. Posey
The Monarch Butterfly is the only butterfly species in North America that migrates, but not all Monarchs migrate. Some prefer to live out their month-and-a-half lifespan in Central America, where cold temperatures aren’t a threat. For those that make the trip, life can be shortened by a hungry bird or the front of a pickup truck, but they usually live longer than their more sedentary cousins.
Migration opens up opportunities for survival. Since they spend more time traveling and eating than reproducing, migrating butterflies tend to be stronger. Plus, the migration allows them to escape feeding grounds heavily infested by the protozoan parasite, Ophryocystis elektroscirrha. If a butterfly is already badly weakened, it won’t be strong enough to make the migration and the rest of the migrating population will be spared infestation.
Curiously, only North American Monarchs show any inclination to migrate. For those in tropical portions of Africa and Asia, the constant warmth provides little incentive to venture forth. Monarchs in Europe often arrive by accident, as a wave of Monarchs did in the UK in 1995. Storm systems crossing the Atlantic Ocean from North America give them air currents to ride. Unfortunately for these accidental migrants, the Alps and Pyrenees, both of which run on an east-west axis, are too great a barrier for Monarchs to cross once winter comes.
Luckily for North America’s Monarchs, our mountain ranges run north-to-south. That means a nice, low-altitude flight through valleys between mountains, rather than an improbable trip at high-altitude competing with Delta Airlines flights stacked up on approach to Atlanta. Mind those turbines!
One of the butterflies’ preferred routes is through Cades Cove, a valley located in the western half of the Great Smoky Mountain National Park. This park is located near the southern end of the Appalachian mountain chain, which stretches from Maine to Georgia in a line parallel to the Atlantic coast. Monarch butterflies are in abundance here during the fall months because their preferred food, milkweed, grows in abundance here. Outside the park, farmers kill milkweed because, well, it’s a weed.
With such a concentration of migrating butterflies passing through, this is the best opportunity for scientists and volunteers from the Great Smoky Mountains Association to catch and tag them. The National Park Service is fully supportive of this, as a lot of information remains to be discovered about the when, where, and why of this fluttery trek.
Strangely, it was only within the last fifty years that the notion of butterfly migration became widely accepted. The idea of such a seemingly-fragile creature flying thousands of miles seemed absurd, so authoritative texts like the tenth edition of A Field Guide to the Butterflies of North America, East of the Great Plains (1951) contained the assumption that they somehow overwintered. Yet when scientists such as Fred Urquhart tried tagging butterflies in the US, only to have them show up in Mexico, there could be no other explanation: the Monarchs were migrating.
So just how does one tag a butterfly? Shoot them with a tranquilizer and clip a transponder on them? No, a butterfly isn’t a bear. A simple sticker featuring a serial number will do the job. It goes on a large cell located in the center of a wing’s underside.
But tagging them isn’t the real challenge, catching them is. Don’t believe me? See how far you can run through a briar patch at 20 MPH. Best not to wear shorts.
As it turns out, Monarch butterflies don’t mess about. They race across meadows, stopping only briefly at a flower or milkweed. This is the only chance to snare them in a net. When they eat, they don’t notice the butterfly wrangler, sneaking up on them like Elmer Fudd on a certain wascally wabbit. Be vewy, vewy quiet…
You can try to catch them in flight, but only those gifted with solid baseball skills can pull this off. Heads up to any Major League recruiters: there’s a park ranger in the Smokies who might be of interest. I watched him snag a fast one right out of the sky, even though it was well over his head.
The weapon of choice is a big, billowy net on a pole about 6 feet long (a bit over 2 meters). Swinging it about endlessly amuses the tourists. If you really want to give them a laugh, run and swing the net, then fall into a briar patch. It’s surprisingly easy to do. Never mind how I know that.
Once they land on a flower and are distracted by their meal, the preferred technique is to swing the net from the side. If you start high and swing down, you’ll probably just catch a lovely milkweed. However, the side attack will almost certainly involve hitting multiple stems en route to the one the butterfly is on. It will quickly figure out something’s up and depart, leaving you with a freshly flattened semi-circle in the meadow. Too much of this and the park service won’t need to mow, as you’ll have done their job for them.
If after 6 hours you manage to catch one (I caught two, which would make me smug if it weren’t for a young woman who snared SEVEN), the next trick is to keep it in the net. This means cinching the net with one hand while still holding the pole with other. Then you have to somehow do both while also reaching through the net’s pinch point to grab the butterfly.
The butterfly will not cooperate with any of this. It will flutter about furiously. I say furiously because one of mine seemed less panicky than determined to fight me for daring to interrupt his meal. I know there are Killer Bees, but Killer Butterflies? Our guide, Wanda DeWaard, showed us the only way to get them to stay still: by grasping the tops of the largest part of their wings along veins on the edge. They feel like cartilage. This edge gives Monarchs more resiliency than many butterflies, as they aren’t damaged if you hold them gently here. The tops of the wings will have symmetrical dots on the rear part if they are male. Females are dot-free.
The stickers are tiny, perhaps half a centimeter in diameter, and crammed with numbers. They go on either wing’s underside on a large, orange, discal cell bounded by black markings. They aren’t heavy enough to affect flight and don’t cause health problems for the butterfly.
The numbers on the sticker correspond to those on a sheet of paper, on which the time, date, location, and gender of the butterfly is recorded. This is entered into a database which allows for quick retrieval if the butterfly is unlucky enough to be caught again. If it’s recaptured, we learn how quickly it traveled and to where it went. One butterfly captured on the day I was there turned out to be a recapture…from two days ago. Apparently, he was in no hurry.
After all the tagging is done, the nice thing to do is find a bloom to put the butterfly on before letting go. They may sit there, a bit stunned from everything that just happened. Or they may rocket over to a nearby tree, where they may feel safer from milkweed-smashing humans.
I wish I could report that my butterflies were caught again and new info was learned about the migration. Alas, my butterflies apparently learned how to avoid capture and now, many months beyond their normal lifespan have probably gone to that great butterfly conservatory in the sky. But I’ll bet they warned their kids to beware of clumsy giants with nets in the Great Smoky Mountains.