Why is the Dakota skipper butterfly disappearing from the region's prairies?

MOORHEAD-The Dakota skipper butterfly has a sad, secretive story to tell.Once free to flit over millions of acres of unmolested prairie, the humble Dakota skipper's range has been drastically reduced over time.It was relatively easy in the 1970s ...
A Dakota Skipper can be seen on a flower in McHenry County, North Dakota in June 2012. Phil Delphey/U.S. Fish and Wildlife Service
A Dakota Skipper can be seen on a flower in McHenry County, North Dakota in June 2012. Phil Delphey/U.S. Fish and Wildlife Service

MOORHEAD-The Dakota skipper butterfly has a sad, secretive story to tell.

Once free to flit over millions of acres of unmolested prairie, the humble Dakota skipper's range has been drastically reduced over time.

It was relatively easy in the 1970s for Robert Dana to find the Dakota skipper, a pollinator that clings to scattered remnants of native prairie that provide its habitat.

"It wasn't difficult to find," he said. "If you could find the prairies you could find the butterfly."

Dana, an ecologist with the Minnesota Department of Natural Resources, shifted his attention from butterflies to plant species for about 20 years, ending in the mid-2000s.

As recently as 2008, when Dana's studied gaze returned to the Dakota skipper, he still found large numbers of the butterflies.

But in the years since, for reasons nobody knows for certain, the Dakota skipper has become an elusive grassland insect, considered threatened by the U.S. Fish and Wildlife Service and endangered by the Minnesota Department of Natural Resources. The shrinking size of its natural domain helps explain the butterfly's population losses, but it's not the whole story.

"Is something else going on in addition to this habitat loss?" said Marissa Ahlering, a prairie ecologist for The Nature Conservancy. "That's kind of the big unknown. What's happening?"

'Maybe they're gone'

The skipper is listed as present in 93 scattered remnants of native prairie-a third of the locations the skipper previously was known to inhabit. Its range extends from western Minnesota up to Manitoba and the southeast corner of Saskatchewan, then into North Dakota and South Dakota.

A naturalist with the Minnesota Zoo, which is working to help preserve the Dakota skipper, last week found 41 Dakota skippers on the Sisseton-Wahpeton Oyate's Lake Traverse Reservation in South Dakota, which is supplying eggs for a captive breeding program. One Dakota skipper also was spotted last week in McHenry County in northcentral North Dakota.

But those scattered, paltry sightings are a mere fraction of what could be logged even a decade ago, as the skipper's surviving populations have dwindled.

One of the most reliable sites for finding the Dakota skipper has been a patch of native prairie less than an hour's drive east of Fargo-Moorhead. Conservationists asked The Forum not to disclose the location, fearing collectors might try to bag some of the few remaining skippers.

The site is less reliable than it once was. On a recent summer morning, Dana began his second day of surveying for the Dakota skipper and had yet to find one.

Early in his vigil, a butterfly flitted by, but it was an alfalfa butterfly, which Dana dismissed as "a classic weed butterfly." He added: "There are plenty of moths out."

Although tipped that the Dakota skipper was in flight in some locations, upon arriving at his destination he found that a wildflower called the purple coneflower-the Dakota skipper's main source of nourishing nectar-wasn't quite blooming.

On the patch of prairie east of the Red River Valley, Dana is eager to learn how plentiful the Dakota skipper remains.

"We're waiting with baited breath to see if the population here takes the same path as everywhere else, which is to decline or disappear. Most places it's disappeared," he said.

The Dakota skipper favors high ground, and can often be seen fluttering around certain plant species they use for food, especially the purple coneflower. The sun was shining-skippers like to warm themselves in the sun-but the morning's stiff breeze hampered efforts, since the butterflies tend to hug the ground in windy conditions.

The adult stage for a Dakota skipper is fleeting, a two-week fling during which they take flight, mate, then die.

"I checked a lot of flowers," Dana said, discouragement creeping into his voice. "It's a bit too early. Either that or maybe they're gone."

Similar paths

The plight of the Dakota skipper largely parallels the decline of the native prairie that once blanketed the nation's midsection. In pre-settlement Minnesota, 10 million acres of prairie provided abundant habitat for an intricate web of grassland species.

"We've reduced the prairie acreage in Minnesota by more than 99 percent," Dana said. Only a few fragments untouched by the plow remain as public or private preserves.

The vast roaming herds of buffalo and elk are long gone from the prairies, leaving naturalists to track the smaller mammals, birds and insects that remain.

Detailed record-keeping of butterflies in Minnesota began in the early 1960s, and monitoring of the Dakota skipper began in the mid-1970s, when Dana was beginning his career.

Dana and others involved in prairie butterfly conservation fear the Dakota skipper could go the way of species that have disappeared, including the Poweshiek skipper, named after a county in Iowa that in turned was named after an Indian chief.

The Poweshiek skipper, also limited to native prairie remnants, now can only be found in four populations located in lower Michigan, Wisconsin and extreme southern Manitoba, said Phil Delphy, a fish and wildlife biologist with the U.S. Fish and Wildlife Service. It once also could be found in Iowa and Minnesota as well as southeastern North Dakota and northeastern South Dakota.

"It's completely disappeared from all these sites that appeared to be in pristine condition," Delphy said.

Biologists worry it could be a portent of what awaits the Dakota skipper.

"For reasons nobody has a clue about, the Dakota skipper seems to be going down a similar path," Dana said.

Theories include pesticides

Although the reason for the sharp decline of the Dakota skipper remains a mystery, suspicion falls heavily on pesticides, which drift onto remnants of native prairie from surrounding cropland.

The Minnesota Zoo, for instance, has tested grasses from several native prairies and found pesticide residue.

Another culprit could be climate change. Also, the dwindling size of the scattered surviving populations of Dakota skippers leaves them vulnerable to shocks of any kind that interfere with the success of a mating season.

The Dakota skipper isn't an impressive butterfly. It lacks the bright colors and dramatic migrations of the Monarch, for example. "They're very small, fairly cryptic-looking butterflies," Ahlering said. "They're not exactly charismatic megafauna."

Yet the Dakota skipper, because it requires biologically diverse native prairie to survive, is an important barometer of the health of the remaining patches of native grassland.

"It's kind of emblematic of high-quality prairies," Delphy said. "Every time we lose a species we lose a part of that greater prairie ecosystem. It's obviously part of our national heritage."

Finds spur hope

After a bit more searching, Dana was surprised to find a single young male Dakota skipper perching on a purple coneflower head that had blossomed last year. He marveled at the butterfly's ability to maintain its perch in the wind.

He kept looking for more than an hour, but didn't find another skipper. A colleague came to the same spot early this week and spotted a dozen Dakota skippers. A modest beginning to their survey, but enough to give Dana hope that the Dakota skipper is still fluttering over the last remnants of unspoiled prairie.