The Schaus swallowtail, one of the world’s rarest butterflies and now confined to a mosquito-infested hardwood island hammock in Biscayne National Park, is marking three decades on the endangered species list this spring with a valiant go at survival.
Scientists have begun releasing captive-bred butterflies, caterpillars and larvae on Elliott Key, where in 2012 one survey detected just four lonely bachelors.
The new releases were bred from four females scientists discovered, to their surprise, on the island last year during the butterfly’s remarkably short life. In the wild, they live barely two weeks. The team managed to collect 100 eggs from the females before letting them go, said University of Florida butterfly expert Jaret Daniels. They tricked the eggs into hatching and laying even more eggs at a Gainesville lab and plan on releasing 200 to 300 of the brown and yellow-banded butterflies in the coming weeks, he said. Altogether, they stockpiled more than 1,000 larvae.
“If we don’t do this, who knows what the history of the Schaus will be,” Daniels said. “They could go extinct in the next five years and we just can’t take that chance.”
Butterflies, the great shape-shifters of the insect world, have long captured the hearts of scientists like William Schaus Jr., the 20th century entomologist who discovered the hand-sized butterfly south of Miami in 1911 and amassed a collection of 200,000 butterflies and moths now housed at the Smithsonian’s National Museum of Natural History. But as butterflies vanish — last year federal wildlife managers announced that two species were likely extinct — they are commanding more attention as a potential indicator of habitat loss and the increasing threat of climate change.
“When you start losing entire suites of butterflies, you know we’re not managing the habitat correctly,” said Mark Salvato, a biologist for the U.S. Fish and Wildlife Service.
Two other rare Florida species, the Florida leafwing and Bartram’s scrub-hairstreak, are expected to be added to the endangered species list this summer, said Salvato, who has spent two decades studying the butterflies and shepherded their designation onto the list.
The listing also helps the butterflies by giving scientists the power to protect their habitat and manage thousands of acres of pine rocklands where they live. Only 10 other endangered species in Florida, including the American crocodile and Cape Sable seaside sparrow, have such protected habitats.
And that matters because butterflies are keenly dependent on their surroundings.
“The species is like the canary in the coal mine,” said Linda Evans, president of Miami Blue, the local chapter of the North American Butterfly Association, which organizes volunteer surveyors to track butterflies. “They’re the species we’re going to see changes in first.”
Florida has roughly 160 species of butterflies, Salvato said. About 25 are considered in peril, the largest concentration of butterflies at risk in the U.S. The tiny Miami blue first signaled that fragile state about 10 years ago when the species dwindled to a single population in the lower Florida Keys, he said. Efforts to save it led to the creation in 2007 of the Imperiled Butterfly Working Group, a collection of scientists, activists and government agents devoted to tracking species in harm’s way.
“It became quite obvious that there were a whole bunch of butterflies that needed that same type of attention,” Salvato said.
The ruby-colored leafwing and gray-and-white-tipped hairstreak, which both live in pine rocklands, landed on the group’s radar as their habitats disappeared. Both can be found in Everglades National Park and eat the same plants. But the larger leafwing is more vulnerable because it requires more habitat. While the fast-moving hairstreak still flutters from Homestead north to the area around Zoo Miami, the leafwing disappeared from the mainland in the late 1980s or early ‘90s, Salvato said. Then came Hurricane Wilma in 2005.
Historically, butterflies could withstand the ravages of storms. But habitat loss accompanied by other dangers like mosquito spraying and poaching can amount to a near-fatal blow, Salvato said. Hurricane Andrew nearly wiped out the Schaus. Wilma similarly decimated the leafwing.
“That was the tipping point,” he said.
The few remaining leafwings now reside in pine rocklands in the National Key Deer Refuge spread between Big Pine and No Name keys.
Salvato doesn’t believe a single “smoking gun” is killing off the butterflies, but a combination of factors unique to each species. Fire, he said, could be the key with leafwings and hairstreaks. Fires historically burned their pine rockland habitats seasonally, making way for tender, new sprouts that caterpillars prefer. If wildlife managers can begin burning the rocklands again, he said, they may be able to bring back the butterflies.
“It takes a while to understand why butterflies fail. Sometimes people do a release and it sticks and we never get to the reason why,” he said.
Or the butterflies, like a brief revival of the Schaus in the 1980s and ’90s after a boost from the Gainesville breeding program, can start out strong but eventually succumb.
“You can perpetuate them for a while, but unless you fix the cause,” he said, “they gravitate back to where you started.”