SC naturalist has tagged 53K monarch butterflies. His findings defy what’s commonly known

On a blistering-hot July day in the Cypress swamp of Francis Marion National Forest, Billy McCord blends in.

Disguised in camouflage clothing and equipped with a long-handle, wide-rimmed net, he was on the chase for monarch butterflies. The naturalist travels alone, wading into the bog, to catch the orange-winged glories and delicately affix a round sticker to the butterflies’ left hind wing, which tracks how long they’ve fluttered and how far.

On a good day, when the butterflies are migrating south, McCord can label up to 500. On a more typical day, he can net closer to 250. For comparison’s sake, he said a few people around South Carolina may “tag 200-300 a season.”

But the practice is nothing new for the long-retired state Department of Natural Resources biologist. Since the fall of 1996, McCord has tagged over 53,000 monarch butterflies in South Carolina.

His nearly three decades of tagging ventures has shed light on how monarchs move through the state, where they call home and what plants they rely on for survival. But recently published research by the DNR reveals an unusual behavior McCord has observed for years: A group of monarchs isn’t leaving South Carolina.

And McCord thinks it’s been happening for centuries.

Staying put

Known to migrate during the fall, heading to Mexico for the winter, some of the insects instead chose to stay in South Carolina.

McCord found them hugging the coast in the winter and fluttering around the state’s coastal plain swamps during the spring, summer and fall.

“People hear about monarchs going to Mexico and they think they’re going to lay in the sun and go to some nice beach,” he said. “They don’t.”

It’s nothing like that.

Monarchs head to mountains in Mexico for the winter, where the daytime high temperatures are in the mid-to-low 50s and the nighttime air cools to 40 degrees. The moisture in the air keeps the butterflies from drying out. The weather there is much like South Carolina’s coast.

McCord was the first in the state to tag a monarch during the winter., he said. He’s found them on James Island and Folly Beach, usually within a half mile from the coast and its moisture-rich air.

In 2018, eight years after he left his post at DNR, McCord teamed up with Michael Kendrick for a five-year study tracking monarchs in the state. McCord was boots on the ground, tagging the butterflies in inland swamps and on sea islands. And Kendrick, an associate marine scientist at the department, wrote and conducted data analysis.

By the end of the study, the longtime naturalist tagged 18,375 monarchs and identified aquatic milkweed as a host plant in swamps from the Pee Dee watershed south all the way to the Savannah River.

Not a month went by that McCord didn’t tag a monarch.

In the winter, the butterflies were in concentrated areas on barrier islands. But during the spring, summer and fall, they covered a broader stretch. McCord found aquatic milkweed — a host plant for monarch’s eggs and caterpillars — in 18 watersheds in the coastal plain. Monarchs were also relying on swallow-wort, what DNR called a relative to milkweed that grows near salt marshes.

“It’s really trying to understand how the monarchs here in South Carolina relate to each other,” Kendrick said. “How are these that are overwintering and along our coast, relate to the monarchs that are using these inland swamps?”

Once there’s a strong grasp on how the different monarchs that stay in the state are related to each other, Kendrick said DNR wants want to compare how other monarch groups relate to the ones in South Carolina.

Under our nose

Since the 1990s, the monarch butterfly population has dwindled by about 90%, according to the National Wildlife Foundation.

A large portion of grassland ecosystems stretching across the eastern monarch’s central migratory path have been affected, the foundation said. Pesticides and herbicides have killed the nectar-rich plants the butterflies rely on. Development has ruined their habitat. And climate change has shifted migration and weather patterns.

But McCord says the monarch population in South Carolina isn’t up against the same challenges.

“My guess is, our population that moves through this area is probably not in any kind of jeopardy and probably has not declined because they don’t have the problems of the Midwestern monarchs,” he said.

There’s no way to get a definite count, McCord noted. However, over the years, the population has stayed stable, he said.

And this has all been under our nose since McCord set out to tag the most well-known butterflies.

“These monarchs are right here and in our backyard,” Kendrick said. “We can add monarch butterflies’ populations and migration patterns as another piece of a unique fauna of South Carolina.”