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Butterflies in decline in South Florida?

By their nature, South Florida’s tropical butterflies have always been ephemeral creatures, coming and going with the rhythms of the life cycle and season. Now they’re just gone.

In what may be an unprecedented die-off, at least five varieties of rare butterflies have vanished from the pine forests and seaside jungles of the Florida Keys and southern Miami-Dade County, the only places some were known to exist.

Marc Minno, a Gainesville entomologist commissioned by the U.S. Fish and Wildlife Service to perform a major survey of South Florida’s butterfly population, filed reports late last year recommending that the Zestos skipper and rockland Meske’s skipper — both unseen for a decade or more — be declared extinct. He believes the same fate has befallen a third, a Keys subspecies called the Zarucco duskywing, and that two more, the nickerbean blue and Bahamian swallowtail, also have disappeared from their only North American niche.

Considering that there have been only four previous presumed extinctions of North American butterflies — the last in California more than 50 years ago — Minno finds the government response to such an alarming wave frustrating.

“There are three butterflies here that have just winked out and no one did a thing about it,’’ Minno said. “I don’t know what has happened with our agencies that are supposed to protect wildlife. They’re just kind of sitting on their hands and watching them go extinct.’’

And the list of the lost could easily grow. South Florida has one of the world’s highest concentrations of rare butterflies. At least 18 others are considered imperiled, reduced to small, isolated populations vulnerable to a host of threats from exotic ants that eat their larvae to a single tropical storm that could blow a colony into oblivion.

Federal wildlife managers insist they are doing all they can do in a state with one of the longest lists of endangered and threatened species in the nation.

“It basically comes down to resources, what we have in terms of money, staffing and those kinds of things that we aren’t always in control of,” said Ken Warren, spokesman for the Fish and Wildlife Service’s South Florida field office in Vero Beach. “We are trying to be as responsive as we can.”

State and federal agencies haven’t ignored the decline. They formed a joint group in 2007 to develop recovery strategies and have supported laboratory breeding programs for signature species like the Schaus’ swallowtail and Miami blue. The service even put a biologist full-time on butterfly problems, Warren said, a level of attention otherwise reserved for high-profile species like the manatee and Florida panther.

But so far, it hasn’t been enough to reverse troubling trends. Experts acknowledge that reviving the rich array of butterflies that once ranged along much of the coast poses significant, possibly insurmountable challenges.

“It’s hard to see for some of the species what really can be done,’’ said Jaret Daniels, assistant curator of Lepidoptera for the Florida Museum of Natural History in Gainesville, who has directed captive breeding efforts for the two others on the brink, Miami blue and Schaus’ swallowtail.

Those booster injections of new butterflies may be the last and best hope, having worked to reinvigorate populations in other states. But so far, they have fizzled in South Florida. Biologists have produced copious quantities of butterflies in protected pens but the lab-bred bugs have never managed to make it in the wild, for reasons still under study.

“With a lot of these butterflies, we don’t necessarily know the ins and outs of them,’’ said Mark Salvato, the service’s lead butterfly biologist. “There are a whole bunch of factors that could be affecting them. It’s hard to find a smoking gun.’’

South Florida’s unceasing growth has clearly hastened the decline. Many of the area’s unique subspecies, originally blown in from Cuba, the Bahamas or other Caribbean islands, developed their distinctive colors or markings in the subtropical comfort of rocky pinewoods and hardwood hammocks, ecosystems now paved over or cut into small pieces.

But there are a long list of additional suspects: Pesticide spraying for mosquitoes can kill delicate larvae. Hurricanes and tropical storms can ravage habitat. Exotic predators have more recently emerged as a major concern, with iguanas eating essential “host plants” that shelter eggs and caterpillars. In some cases, invasive predatory ants may have supplanted native varieties that once protected butterfly larvae in symbiotic relationships.

A lack of breeding partners and genetic diversity also could cripple populations. Climate change and land management may also have impacts. .

What is particularly puzzling is why many butterflies have declined in otherwise healthy habitats in places like Everglades and Biscayne National parks, protected areas where mosquito spraying is prohibited. Last summer, for instance, teams scoured Elliott Key in Biscayne Bay, once prime breeding ground for the Schaus, hunting for enough to jumpstart a new breeding effort. They found only a handful — and not one female. They’ll try again in a few months.

And the Miami blue, once common along the coast from Daytona Beach to the Dry Tortugas, has now been reduced to the Marquesas islands west of Key West.

“It makes no sense from an ecological standpoint,’’ Minno said. “They should be up in the biggest islands with the most habitat.’’

While other butterflies are also in decline globally, South Florida’s problems are acute, with roughly a third of the 100 or so varieties known to live south of Lake Okeechobee at risk, said Elane Nuehring, past president of the Miami blue chapter of the North American Butterfly Association.

“We are sort of the capital of declining species,’’ she said.

Though butterfly watching doesn’t rival bird-watching, the delicate creatures are fascinating for many people, said Daniels, calling them “as close as you can get to the panda’’ in the insect world.

Scientists also say their disappearance is more than damaging than simply erasing fluttering flecks of color from the landscape. They are part of complex food webs and rank next to bees among the most important pollinators. They also are indicators of the health of the forests and hammocks they call home, Salvato said.

“When you start to lose the butterflies, something broader is going on,” he said.

Not everyone, however, is quite ready to pronounce the missing butterflies dead — at least not yet.

The Fish and Wildlife Service, which received Minno’s extinction recommendations late last year, is pondering its next steps.

Butterflies in the past have vanished for years only to make surprise reappearances. The Miami blue, for instance, was considered unofficially extinct after Hurricane Andrew in 1992 until the discovery of a colony of 50 in Bahia Honda State Park seven years later. Those disappeared in 2001 but more were later found in the Marquesas.

The Meske’s also once before went missing for a decade, Salvato said. “It’s a very indistinct butterfly. It’s not hard to overlook.’’

Daniels agreed it’s too soon to make a pronouncement. Many of the butterflies have brief life spans and live in areas difficult to fully survey. “That’s the inherent challenge, having enough data to verify that something is gone,’’ he said.

The service’s Warren said the butterflies Minno believes are gone also fall in a bureaucratic “gray area.” None of them were yet in the official pipeline for listing. Only two, the Schaus and Miami blue, have endangered status. Two others, the Florida leafwing and Bartram’s scrub-hairstreak, have been elevated to “candidates.” The agency won’t add something just to turn around and stamp it extinct.

“There is no requirement for us to do anything as far as a formal announcement that it’s gone,’’ Warren said. “At this point, I would say the smart thing for us is to take the recommendation under consideration and give it a little time to see what happens.’’

Minno argues something is wrong when butterflies vanish before the agency charged with protecting them even begins its process of declaring them in trouble. Environmental groups have expressed similar frustrations. In 2011, the Arizona-based Center of Biological Diversity sued the Fish and Wildlife Service over a backlog of 757 species awaiting listing.

Federal wildlife managers blame the sluggish action on shortages of money and resources, estimating the cost at simply listing a species as endangered or threatened at $150,000 to $300,000. In many states, there also has been strong political resistance to additional listings from landowners and developers.

Minno is persuaded the Zestos and Meske’s skippers are gone forever. His survey was supposed to take two years, he said, but he spent six on it, logging thousands of hours in the field. Other experts also did the same. No one has spotted any of them, in any stage of life, from larvae to butterfly.

“I thought I was going to find some at some point so I just took a lot more time,’’ Minno said. “They’re just not there.’’