The piercing orange of butterflies fluttering along the winter sea breeze on Folly Beach caught the eye of a Charleston biologist a few years back. That chance encounter led him to help discover an entire population of monarch butterflies that spend winter along the South Carolina coast. Most normally migrate annually to Mexico.
“We found wintering monarchs along 96% of the South Carolina Atlantic coastline,” said John “Billy” McCord of James Island, a longtime biologist who participated in a study from 2018 to 2022 under the South Carolina Department of Natural Resources (SCDNR). Since 1996, he has tagged more than 53,000 monarchs in his field studies of the endangered butterfly species.
The new SCDNR study was published in the peer-reviewed journal Scientific Reports in June. The findings are important because it could mean there is an Atlantic coastal population of monarchs with unique migration and breeding patterns that differ from what biologists attribute to North American monarch butterflies, McCord said.
McCord carried out year-round field work with a group of volunteers for the recently published study, which included capturing monarchs with nets along the South Carolina coastline and applying an adhesive synthetic resin-based tag with identification codes.
Locally, McCord tagged monarchs throughout barrier island and sea island habitats located near open water on Folly Beach, James Island and in Mount Pleasant.
Monarchs were also tagged in bottomland hardwood forests and cypress-tupelo swamps in parts of Charleston and Berkeley counties to help gather information about the insect’s breeding and migrating habits.
Wintering habits uncovered
Monarchs were found in December, January, February and early March from northern Myrtle Beach through the Charleston area and all the way down to Daufuskie Island, McCord said.
“Until we started studying this, nobody had scientifically recorded the presence of monarchs in coastal South Carolina during the winter,” he said.
As part of the five-year SCDNR study, he tagged 18,375 monarchs in the coastal South Carolina region and worked to recapture tagged butterflies to see how long the butterflies stayed in the area in order to help determine seasonal migration patterns.
“The monarchs that come here are most likely from east of the Appalachian mountains,” McCord said. “The ones that winter here may come from the New England area and even southern Canada. There were monarchs at Folly Beach that were tagged in Canada. I’ve also recaptured one that was tagged on the shore of Lake Erie in upstate Pennsylvania. I recovered several that were tagged in Cape May, New Jersey.”
McCord said he believes this evidence points to a separate Atlantic coastal monarch population not affiliated with the Midwestern monarch population known to migrate to Mexico in the winter. But he said more evidence needs to be collected, such as genetic specimens, and more field work needs to be carried out in Georgia and Florida to help map out the behavior of the monarchs east of the Appalachian mountains.
“We need to figure out how many populations there are and what their relationship is to each other,” he said. “That’s why genetics are important.”
Conservation required
The SCDNR study also indicated monarch butterflies live in South Carolina year-round, McCord said. This new information is most important in terms of long-term conservation law, since monarchs are classified as an endangered species.
“There’s more to be learned to fully be able to understand exactly what’s going on and to give the proper protection to monarchs,” he said.
In addition to sea island habitats in the winter, monarchs rely on inland swamp habitats in South Carolina throughout the spring, summer and fall. These habitats are replete with the aquatic milkweed a monarch population needs for laying eggs and its caterpillars need for food.
McCord said preserving the swamps that house the main food source monarchs require is of the utmost importance.
“If you kill the milkweed, then you basically get rid of monarchs,” he said. “It’s important to try to protect [swamp] areas into the future so they will still be used by monarchs. Land conservation is what we need.”
Monarchs are designated as an endangered species primarily from what’s happening in the Midwest, he said.
“The Midwestern monarch population has undergone somewhat of a crash over the past couple of decades, and that’s primarily because of ethanol [farming],” he said. “There has been something like 5 million acres or more that has been transformed from meadowland and grassland into row crops to produce ethanol.
“And at the same time, there’s a version of Roundup created that can be sprayed right over corn and soybeans, and it doesn’t kill the corn or soybeans, but it kills everything else — including milkweed. So there’s a tremendous loss of habitat for monarchs in the Midwest, which is where most of the butterflies that [migrate] to Mexico [originate].”
And since the effects of global warming are yet unknown, McCord said, the newly discovered wintering habits of Atlantic coastal monarchs may change.
“[Monarchs] may expand their wintering range farther north and reduce their range to the South because it may start getting too warm for them along the southern part of the coast. We don’t know that yet.”
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