Surviving on a Wing and a Prayer
Once numbering fewer than 100, the endangered Schaus swallowtail butterfly has made a steady comeback in Florida with help from a determined scientist
- Jeff Klinkenberg
- Jun 01, 1997
Thomas Emmel hunkers on the edge of the dark and humid subtropical forest known as a hammock. The area is the part of the Florida Keys that few tourists ever see. In the steamy hammock, there is no Jimmy Buffett on the juke box. The soundtrack is provided by the whine of mosquitoes. "They're pretty serious here. You'll want to put some repellent on," Emmel advises his companions.
Emmel endures the humidity and the mosquitoes with little complaint. The wilderness coastal forests of the upper Keys are where he stalks what some entomologists call North America’s rarest butterfly, the Schaus swallowtail. A University of Florida zoologist, he has studied the insects for more than a decade and has played a major role in their return from extinction's brink. The work seldom has been easy. For the love of butterflies, he has suffered through nerve-wracking federal and state budget crises, and spent thousands of dollars of his own money. He has sidestepped rattlesnakes coiled in the shade, toxic plants that put legs and ankles at risk, and scorpions that scurry through the leaves.
Despite the dangers of working in this strangely hostile world, Emmel has remained focused on his work, which is fortunate for the endangered butterflies. He has learned their natural history and discovered their habitat needs. In 1992, before Hurricane Andrew roared through the Schaus' only known range, he initiated a captive propagation program that the U.S. Fish and Wildlife Service (FWS) hailed as a major success.
"He's an incredible teacher," says David Wesley, the deputy assistant regional director of the FWS's Pacific Northwest office, and Emmel’s former funding supervisor in Florida. "He believes totally in what he is doing."
From a few dozen butterflies that clung to existence only a decade ago, the wild population has grown to 1,000 or more. The Schaus could soon become the first invertebrate to be removed from the U.S. Endangered Species List. But some questions about the species’ future still remain, and at this writing Emmel’s project is in limbo while federal authorities decide what steps to take next to ensure the insect’s recovery.
The story of this fragile butterfly begins in 1898, when a physician named William Schaus, visiting Miami to treat yellow fever victims, noticed a butterfly he had never seen before. A passionate lepidopterist, he later named it Papilio aristodemus ponceanus, but it soon became known as the Schaus swallowtail. Although it resembles the giant swallowtail butterfly that is common in this country, the Schaus is slightly smaller, its wings spanning just over 2 inches. It evolved to maneuver in dense forests on small tropical islands, flying low and slow to weave through vegetation and spider webs. Its natural enemies include birds, lizards and spiders. To help escape them, the Schaus can do something few other butterflies are capable of doing: It can stop in mid-air and fly backwards.
The year after William Schaus described the species, its problems began in earnest. In 1912, a new railroad connected Miami with Key West. Developers rejoiced: Millions of dollars were to be made selling off the country’s remaining tropics. A hurricane destroyed the railroad in 1935, but a series of bridges brought tourists and residents by the thousands to the Keys. They inevitably built homes and resorts in butterfly habitat--areas considered prime real estate because they were usually the highest land found along the ocean.
Virtually all the hammocks vanished from mainland South Florida and the Keys during the land boom of the Roaring Twenties. Through the 1960s, the upper Keys were the best place to see the butterflies; in the 1970s, the creatures became scarce even in the undeveloped forests of Key Largo. The last healthy colonies clung to life on the islands of Biscayne National Park. In 1977, the butterfly was listed as a threatened species. In 1984, FWS authorities asked Thomas Emmel to determine the species’ true population. He found fewer than 70. That year, the butterfly was upgraded to endangered species status.
As he looked further into the situation, Emmel wondered if the Schaus’ downfall had something to do with mosquitoes. Hammocks are bug-infested places, and he was sure the demand for mosquito control was threatening to wipe out the butterflies. After World War II, DDT was applied throughout Florida, and when it was banned because of public health concerns, new potent chemicals were introduced.
In 1972, the Monroe County Mosquito Control District began spraying certain pesticides over Key Largo’s tropical hardwood hammocks, located between two of the most developed sections of the Keys. That was the year the Schaus swallowtail population began its precarious dive.
In the Keys, mosquito control officials claimed it was coincidence that the insects were dying. Environmentalists suspected otherwise--the pesticide-free islands of Biscayne National Park supported a respectable butterfly population.
In 1987, Emmel and his students began testing mosquito pesticides on a plentiful species, the giant swallowtail. They discovered the pesticides used to kill adult mosquitoes in the Keys were 400 to 4,000 times greater than what was needed to kill butterflies and other beneficial insects. Still, the bombing raids against mosquitoes continued.
Four years later, Emmel organized a statewide scientific forum in Gainesville to discuss the impact of pesticides on wildlife. Soon, state and federal agencies began lobbying the mosquito control district in the Keys to stop spraying at least on public lands, especially Crocodile Lake National Wildlife Refuge and the Key Largo Hammocks State Botanical Site, both butterfly habitats. Finally, the mosquito control district agreed to route its airplanes away from butterfly territory during spring when the insects were flying. The Schaus swallowtail population enjoyed a modest comeback.
Emmel hardly celebrated, however. For years, he had worried that a hurricane could wipe out an isolated Schaus population. He proposed a captive propagation program and the release of butterflies in their historic range. He got the necessary permits in 1992.
That June, Emmel and some students visited Elliott Key in Biscayne National Park. They caught butterflies, confined them in cages and waited patiently for them to reproduce. Emmel released the butterflies but took 100 eggs back to Gainesville. They soon hatched into caterpillars. After stuffing themselves on their only known food--the leaves of wild lime and torchwood trees that Emmel nurtured in a greenhouse--those caterpillars developed into their next stage, the inert and shell-like structure known as the pupa.
Two months later, Hurricane Andrew scored a direct hit on Biscayne National Park, the butterfly’s last wild stronghold. A few days later, Emmel visited the area. The storm had leveled all vegetation and swamped the island with 10 feet of sea water. He did not find any signs of swallowtail pupae. The following spring he returned to look for butterflies in flight. In two weeks, he counted 17.
At that point, the largest population of the Schaus swallowtail in the world was in Gainesville. In Emmel’s lab, and at the homes of students, the butterflies were emerging from a long sleep. They laid more eggs, which turned into more caterpillars, which became more pupae. By early 1995, Emmel had 2,000 pupae.
That spring, Emmel and his students carried foam boxes filled with Schaus swallowtail pupae into a thick forest in the upper Keys. While one student glued the pupae--grayish pellets about 1 inch long--on trees, another mapped their locations. Emmel wanted to keep track of each of the 764 pupae he released.
A month later, heavy rains began, triggering metamorphosis in the Schaus swallowtails. Emmel and his students returned to South Florida to search for butterflies. And for the first time since 1924, the swallowtails were seen flying on the mainland. Meanwhile, in Key Largo, the insects flitted through hammocks in numbers not seen in years.
"I was hoping we’d find even more," Emmel recalls. Two late-season cold fronts had dropped thousands of migrating warblers into the hammocks of Key Largo. Emmel believes the hungry birds ate between 60 and 90 percent of his pupae at the seven release sites. However, he and his students found good signs of reproduction: tiny pearllike eggs clinging to undersides of wild lime trees and scores of caterpillars, which would become pupae, the stage that lasts about 10 months.
Last spring, Emmel decided not to place pupae in South Florida’s hammocks; he released adult butterflies instead. "Adults should have a better chance at survival," he says. In the wild, a Schaus adult lives about five days--long enough to reproduce.
At the release, FWS staged a media day and as Emmel looked on, freed butterflies landed on the heads of bureaucrats, politicians and television camera crews. The event prompted international publicity.
Emmel, though, was secretly fuming at the time. Congressional budget cuts, two federal-government shutdowns and questions about some of aspects of his program from a new FWS official in South Florida had delayed his funding for more than a year. To keep the project going, Emmel was forced to pay for it out of his own pocket. That meant seeking donations from butterfly fanciers around the world and borrowing money from the University of Florida.
Impatient for his money and a commitment for the future, Emmel went over the heads of his federal supervisors in South Florida. In January, authorities with FWS’s Atlanta office audited Emmel’s expenses and agreed that he should be reimbursed $75,000 for past expenses. That enabled the scientist to repay his loan to the University of Florida. And Emmel was hopeful that he would recover the $18,000 of his own money he spent last year on saving the endangered butterfly.
In February, federal authorities decided to continue with the Schaus swallowtail program this year, and to leave Emmel in charge of the butterfly’s recovery effort. For the University of Florida scientist, it was welcome news.
"The butterflies that are now out there are surviving well," says Emmel. "But because their range is so confined, I’m concerned about what will happen to them if another catastrophe strikes like Hurricane Andrew. For the species to fully recover, we need to continue establishing new populations. In my view, there’s still work to be done."
Jeff Klinkenberg is a writer for The St. Petersburg Times. His most recent book is Dispatches from the Land of Flowers (Down Home Press, 1996), a collection of essays about Florida