Butterfly Tagging

Monarch feeding on groundsel

On Friday, the Dewees Island Conservancy sponsored a butterfly tagging program on Dewees Island with long-time island friend and fantastic Naturalist Billy McCord. Everyone I told about this responded with a befuddled, “how can you tag a butterfly?” I couldn’t wait to find out.

It turns out that we are only actually tagging monarchs, because they are the only ones that migrate. According to Kansas University’s Monarch Watch program:

In all the world, no butterflies migrate like the Monarchs of North America. They travel much farther than all other tropical butterflies, up to three thousand miles. They are the only butterflies to make such a long, two way migration every year. Amazingly, they fly in masses to the same winter roosts, often to the exact same trees. Their migration is more the type we expect from birds or whales. However, unlike birds and whales, individuals only make the round-trip once. It is their children’s grandchildren that return south the following fall.

Since butterflies are cold-blooded, they only fly when the sun can warm them. Monarchs have a genetic mutation that allows them to store fat; it also gives them the ability to shiver; to mechanically warm their muscles.  The last generation to hatch in the fall stores fat in their abdomen, in order to travel long distances and live through the winter.

This fat not only fuels their flight of one to three thousand miles, but must last until the next spring when they begin the flight back north. As they migrate southwards, Monarchs stop to nectar, and they actually gain weight during the trip! Some researchers think that Monarchs conserve their “fuel” in flight by gliding on air currents as they travel south. This is an area of great interest for researchers; there are many unanswered questions about how these small organisms are able to travel so far.

To tag them, you first catch them with a butterfly net.  Watch out for bees and wasps, who may be nectaring on the same plants.  Billy usually catches a large number before tagging them, usually out of the wind. The best place to hold a monarch is along the forewing, which has the hardiest structure. Butterflies are covered with tiny scales, and we need to be careful not to strip the scales.   Billy can actually hold butterflies between his lips; if he is going to be a while before tagging them, he places them in glassine envelopes in a cooler with an ice pack and a damp paper towel to provide humidity. Astonishingly, this calms the butterflies by metabolically slowing them down a bit. When it is time to tag them, he records their size and gender (male monarchs have a black mark which may be a scent gland of sorts on their lower wings, and the females have thicker black bars) the date, the nectar source, and the condition of the butterfly. He assigns them a condition number from 1 to 5 based on the level of degradation of the wings.  To keep track of host plants and locations, he uses sequential envelopes and if he captures a monarch on a different plant, he includes a specimen of the new plant with the butterfly in the envelope.

Occasionally, like today, he catches a mating pair. Over the years he has observed that the males in late season couplings tend to be rather tattered– as if they realize that this may be their last chance to pass on their genetic material.

To tag the butterflies, he gently slides the butterfly into a cardboard splint so that the wings are separated and held in place by a rubber band. A tiny tag, made of lightweight polypropylene with special 3M ¨ adhesive, is placed gently on the back.

When I tried this myself, I eventually learned to have the tag only touch the edges of my fingernails to avoid getting stuck to it! Kansas University, which oversees the tagging project, only requires the date, location, gender of the butterfly, and full tag number, so that’s what Lori and I enter on the data. Tags are purchased in lots of 25, and the Dewees Island Environmental program has 50 to do this season. The price funds some of the research in processing, so people who volunteer with monarchwatch actually purchase the tags they use.

When a butterfly with a tag is recaptured, the tag number is sent to Kansas University and data is collected (and published) about when and how far the butterfly has flown. The most recent assumptions have been that migrating butterflies east of the Rockies have all wintered in Mexico, but because so few of the locally tagged butterflies (3 of 18,000 have been recaptured in Mexico), Billy McCord surmises that our coastal butterflies head somewhere else… the mountains of Caribbean nations in the Dominican Republic, Haiti, or Cuba… but more science is needed to prove the theory. In addition, some of ours may actually overwinter right here. He has recaptured tagged butterflies on Folly Beach, even after a very hard freeze.

Why tag them?
The whole project seems to serve a variety of purposes. Once you have gingerly held this tiny bit of beauty, felt the incredible ability in its wings and grasping feet, and wished it well along its journey, you are more likely to care about protection. And it is apparently clear that protection is increasingly important, as threats from deforestation, pesticides, habitat loss, and even climate change may be taking their toll. The 2011 Monarch pre-migration newsletter says:

The great migrations of the 90s are a thing of the past. In the future, we can expect overwintering populations in Mexico of 2-6 hectares. The main reason for the decline is loss of habitat.
Monarch habitat has been reduced by at least 140 million acres in the last 10 years – about a fifth of the total breeding area available to monarchs has been lost. At least 100 million acres of habitat has been lost due to the adoption of herbicide resistant corn and soybeans.

What else might help?
It looks like there are a lot of ways that ordinary citizens can make a difference, even in their own yards. Dewees Island is already ahead of the game in terms of not using pesticides and using native plants for gardening. Although milkweed is the most familiar of the host plants, there is only one variety of milkweed native to the South Carolina Coastal plain, and therefore eligible for cultivating on the island. Not to worry, however, there is a vine near the dunes called swallowwort, which is the most commonly used host plant for Monarch butterflies on the island.

swallow-wort vine

In your yard off the island, think about using fewer pesticides and herbicides and about planting milkweed from seed for egg-laying and caterpillars to grow on.  Allow some groundsel, aka salt myrtle to flourish in your yard, despite its scruffy appearance.  You can actually get seeds and start an official “monarch waystation” at your home, office, or school.


Click here for information about the monarch lifecyle.

This Post Has One Comment

  1. Elizabeth Middour

    Good job, Judy! I found this article very interesting and your supporting photographs are incredible. I have always loved this time of year, when the Monarch seems to be everywhere. It is nice to know why they are here and where they are going! Elizabeth

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