The fate of a blue butterfly
by Eric Sorensen | © Washington State University
A century or so ago, late spring in Oregon’s Willamette Valley saw waves of delicate blue and brown butterflies across a million acres of prairie, lighting on equally delicate lupines to lay their eggs.
At least we can imagine it that way. The region has long since been settled and farmed, and the prairies were the first to go. With them went the vast number of Fender’s blue butterflies and their host plant, the Kincaid’s lupine. The butterfly appeared to the eye of science only briefly, first in 1929, and occasionally until 1937. Then it vanished. Scientists assumed it was extinct.
In 1988, Paul Severns, age 12, collected three males and three females. The next year, Oregon entomologist Paul Hammond spotted a Fender’s blue while hiking outside Corvallis. Severns’s discovery went unnoticed; his reference book didn’t say the species was extinct. Hammond’s sighting made The New York Times.
Over the following years, scientists, conservationists, and land managers set to salvaging pieces of the original prairie, less than half a percent of which remains. In 2000, the U.S. Fish and Wildlife Service put the butterfly in the “endangered” column of the endangered species list, meaning it is at risk of going extinct. The Kincaid’s lupine was listed as “threatened.”
Cheryl Schultz, an associate professor in the School of Biological Sciences at WSU Vancouver, has now spent almost two decades following the Fender’s blue, mostly in five-minute spurts. She started out watching them with no known pattern in mind. But over time she has found ways to describe their flight with a mathematical formula, using it to come up with a way of helping make the most of their shrunken range.
“By understanding the mechanisms of how they move across the landscape,” she says, “we can ask questions like, ‘Well, what are they going to do if we restore it like this? What are they going to do if we restore it like that?’”
Schultz arrived in the Willamette Valley in 1993 as a University of Washington doctoral student. She had witnessed the spotted owl debate while in college and was intrigued by the potential of science to explore “the gray areas” overlooked in the good-vs.-bad, black-vs.-white portrayals of environmental issues.
“It’s a question of finding balance,” she says. “When are the species declining and how? What’s impacting them? How do we work within the system to say, ‘What kind of changes can we do so we can protect the species, but also work with the human populations that are there?’”
Schultz concentrated on the math of conservation biology and learned about population viability modeling—which populations can sustain themselves, which might crash. She was interested in corridors linking areas of habitat when she came upon the story of the Fender’s blue butterfly and realized it offered a specific, narrow set of questions.
As you might imagine, she spent a lot of time simply looking at the butterflies. One thing making that possible is they’re weak flyers. If you don’t confuse it with the similar-looking silvery blue butterfly, you can spend a day tracking one as it flies about at eye height, oblivious to the observer. You might even spend a butterfly’s lifetime—9.5 days, on average—following one. Typically, Schultz would spend five minutes on one’s trail, dropping small flags every time it landed or every 20 seconds on the wing to get a flight path.
Schultz and her students saw that at the edge of a Kincaid’s lupine patch the butterflies seemed to notice they were leaving their habitat. Sometimes they would come back, displaying a bias to return that could be described in a mathematical formula.
One thing became clear: The Fender’s blue would not profit by having corridors to link larger sections of habitat. The corridor under consideration, a six- to eight-foot-wide lupine-strewn stretch along Amazon Creek near Eugene, would not work.
“What we found was, no, they won’t stay in a corridor,” says Schultz. “They won’t stay in an area that narrow.”
But an analysis of settlement records in the valley showed it used to have patches of prairie, and often many of them, and they were frequently less than half a kilometer apart.
Measurements by Schultz and her students found butterflies could fly half a kilometer in a lifetime if they were in lupine habitat, and almost two kilometers if they got outside of it.
She suggested “stepping stones” of habitat linking larger refuges. Over several generations, butterflies from different populations could intermingle. They could mix their genes and prevent interbreeding. If one population went extinct, its habitat could be recolonized by individuals from another population.
“It makes it more feasible that the butterflies will be able to fly back and forth,” says Ed Alverson, stewardship ecologist for The Nature Conservancy, which has ten sites in the valley with the butterfly, the Kincaid’s lupine, or both. “That’s an example of how the research feeds into the conservation process.”
Several of the areas Schultz identified as stepping stones are now designated critical habitat. They’re being restored under a management plan she helped design. But the butterflies aren’t yet out of the woods, so to speak. In 2003, she said only one of 16 populations had a better than 90 percent chance of making it through the century. Now, she says, their odds have probably improved, “but we haven’t done the analysis yet.”
Meanwhile, Paul Severns, whose 1988 discovery of Fender’s blues is largely unacknowledged, has received an Oregon State University PhD in the genetics of Kincaid’s lupine. He’s now a postdoc in Schultz’s lab working on another imperiled butterfly, the Taylor’s checkerspot.
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