Rescue effort hopes to head off extinction of Minnesota butterflies

The future of an imperiled Minnesota butterfly may depend on how it handles life inside a Sanyo cube refrigerator. That's where more than 300 Dakota skipper caterpillars will spend the winter, snuggled in paper towel beds inside plastic cups, to simulate their normal home clinging to snow-covered prairie grasses.

The Minnesota Zoo's experiment to create an "insurance population" of Dakota skippers represent a small but heroic effort to counterbalance whatever is killing them in the wild.

On Oct. 23, the U.S. Fish and Wildlife Service announced that the Dakota skipper is now a threatened species. Another prairie butterfly that's even worse off, the Poweshiek skipperling, has been added to the endangered list.

The populations of these butterflies have collapsed over the past 15 years, and they have disappeared from 75 to 96 percent of the places where they were known to flutter and crawl. No one knows whether habitat disturbance, pesticides, climate change or something else is blame, but they may be a memory by the time we find out.

Once so common that no one bothered counting it, the Poweshiek skipperling was last seen in Minnesota in 2008. Maybe 500 hang on in isolated spots in Michigan, Wisconsin and Manitoba.

"It's a catastrophic decline that has to rank it as one of the most endangered species on earth," said Erik Runquist, a biologist who runs the zoo's prairie butterfly conservation program.

Biologists say the Earth is experiencing the sixth mass extinction in its history. Unlike the asteroids, volcanoes and other impersonal phenomena implicated in previous die-offs, this one is on us.

Minnesota's contribution to this tragedy is happening on its prairie, a rich and diverse ecosystem that has been nearly plowed into oblivion. Only 1 percent of native prairie survives, in patches between acres and acres of corn and soybeans.

Still, biologists thought that they had adequately protected enough of these places at least to sustain the two butterfly species. As they walked through the prairies, they were alarmed at what wasn't there.

"There's plenty of nectar, plenty of larval food plants, and the species are just gone," said Phil Delphey, a Fish and Wildlife Service biologist.

It's a particularly tricky task to save these butterflies, because the entire species has to renew itself every year. Bad weather or changes to its habitat could wipe out a local population forever.

This year, the zoo and the Minnesota Department of Natural Resources received a total of $625,000 from the Minnesota Lottery's environmental fund for the captive breeding program, increased habitat monitoring and genetics research.

Over the last two summers, the butterfly biologists traveled to a secret spot in South Dakota, timing the trip to coincide with the butterfly's two weeks in winged form. They captured some females, brought them back to a motel room and waited while they laid eggs inside paper cups.

Their job done, the females were released back to the prairie, while the eggs were spirited to the zoo in Apple Valley. They hatched into larvae. Some will spend the winter hibernating in plugs of prairie dropseed and little bluestem inside plastic tubes, which are currently stored in an outdoor enclosure.

The rest sleep in the fridge marked "No food" in the program laboratory.

If all goes well, when spring turns to summer, the insects will turn into inch-long, fuzzy orange butterflies ready to breed and flit among the waving grasses. The project will only succeed, though, if they have somewhere to go back to.

These butterflies lack the drama of monarchs, the utility of honeybees and the charisma of moose, other local species in trouble. They have value as pollinators, and their decline could indicate bigger problems with what we're doing to the land, but neither of those points will likely save them.

The most persuasive argument for keeping them around is the irrevocable alternative.

"The world is a lonelier, smaller place without them," Runquist said.

Contact James Eli Shiffer at james.shiffer@startribune.com or 612-673-4116. Read his blog at startribune.com/fulldisclosure.