SAN JUAN ISLAND — The southern end of San Juan Island is home to a species more imperiled than the polar bears of the Arctic and the tigers of Asia.

This species is also harder to spot than those large, iconic animals. It flits by unsuspecting islanders and tourists alike in a matter of seconds, a blur of white.

It’s the island marble butterfly, an increasingly rare species that may soon become the 10th endangered species — and the second butterfly with that protection — in Washington state.

The U.S. Fish & Wildlife Service proposes listing the island marble butterfly as endangered and designating 812 acres on the island as critical habitat for the species.

The federal agency is responsible for fulfilling the purpose of the Endangered Species Act, which is to protect and restore species that are endangered, meaning at risk of extinction, or threatened, meaning at risk of becoming endangered.

Despite voluntary conservation efforts on behalf of federal, state and local agencies, the island marble butterfly population has continued to decline in the 20 years since it was discovered on San Juan and Lopez islands.

The butterfly, with wings each about the size of a quarter that are white on top and a marbled yellow and green on bottom, is now found only within the American Camp portion of San Juan Island National Historical Park.

In 2017, about 200 of the butterflies were seen during an annual survey. It’s believed many of those are the product of a captive rearing project the National Park Service has been leading since 2013.

Those who have been working to protect the island marble butterfly said it’s about time the species was listed as endangered.

“This has been a long time in coming ... This animal is really imperiled and we need the community to start paying attention to it,” San Juan Preservation Trust Stewardship Manager Kathleen Foley said.

She’s one of several who said they hope the listing will make more government funding available for ongoing efforts to save the species.

“This butterfly has been hanging on by a thread for so long,” Foley said. “I’m hopeful that whatever money and attention accompanies this listing will be enough to boost up its numbers again.”

The island marble butterfly was believed to be extinct after it disappeared in 1908 from British Columbia’s Gulf Islands.

In the years since the species was discovered in the San Juan Islands in 1998, it has disappeared from four of five locations and the population has declined from thousands to hundreds, according to the Fish & Wildlife Service’s proposal.

A habitat issue

Throughout its yearlong life cycle — just six to 10 days of which are actually spent as a butterfly — the island marble butterfly relies on a few types of flowering plants for survival. That limits its habitat to prairies and lagoons where those plants are found.

It also puts it at risk of being eaten by grazing deer, inundated by coastal flooding, trampled by park visitors or cut down by lawn mowers, according to the Fish & Wildlife Service proposal.

Being eaten — by deer as well as predatory spiders and wasps — causes an estimated 60 percent of island marble butterfly deaths, according to the proposal.

The proposal states increasing temperatures, sea level rise and more frequent storm surges associated with climate change could further impact the butterfly’s habitat.

A 2006 winter storm destroyed half of the plants where the butterflies lay their eggs in the lagoons, according to the proposal.

Meanwhile, increasing temperatures could affect the time of year when island marble butterflies emerge from their cocoons, putting them out of sync with plant growth and leaving them without a sufficient source of food.

The island marble butterfly is further at risk because its small population makes it more susceptible to being annihilated during a single incident such as a fire or flood, according to the proposal.

“The more we find out about these things it’s like, ‘Oh my God, the odds are just stacked against them,’” Foley said.

That’s why several agencies have worked to ensure the island marble butterfly has habitat available. They have fenced about 9.5 acres of habitat on San Juan Island to protect plants from deer.

Fenced areas at American Camp protect a combined 8 acres of habitat. Those areas are awash this time of year with the yellow flowers of the mustard plants where the butterflies lay their eggs and the next generation begins its arduous journey from egg to butterfly.

Fencing at San Juan Preservation Trust and San Juan County Land Bank properties protect another 1.5 acres of mustard plants and other flowering varieties the butterflies use as sources of food, including purple sea blush.

“The whole idea was to create permanent butterfly gardens, essentially,” Foley said after pointing out the types of flowers at one of the protected areas. “Now we just need to add butterflies.”

Rescue, raise, release

In a cabin-like facility on the outskirts of American Camp, National Park Service biologist Jenny Shrum spends much of her time during spring and summer watching island marble butterflies move through their various life stages.

Before becoming white-winged butterflies for a fleeting week or so between April and June, island marble butterflies begin as tiny orangish-red eggs. After about a week, caterpillars emerge that are about the size of the letter “l.”

After about a month of growth, the caterpillars tuck themselves into about inch-long cocoons. That’s where island marble butterflies spend the majority of their life cycle before emerging ready to take flight.

This time of year Shrum, who leads the park’s captive rearing program, collects mustard plants with the tiny eggs attached and in the rearing lab watches caterpillars emerge, grow and build their cocoons. She also waits for those that have been in cocoons for nearly a year to break out of them and spread their new wings.

At sand dunes north of South Beach on Tuesday, Shrum released five island marble butterflies that had recently emerged.

“This is the first time this critter has ever been exposed to real sunlight, real wind out of the lab,” she said while waiting for one of the butterflies to take flight.

Shrum has now released hundreds of the butterflies through the captive rearing program, which she said produced 75 butterflies in 2014 and is expected to produce about 160 this year.

By the end of the summer, about 500 lab-reared butterflies will have been released through the program.

“We’ve been bringing in more eggs and caterpillars so that we’re releasing more butterflies every year,” Shrum said.

In the lab, University of Washington graduate student Graham Crawbuck sat Tuesday hunched over a cluster of yellow flowers on a sprig of a mustard plant. On the plant he counted four future butterflies: three eggs and a recently-hatched caterpillar.

“It’s exciting to see,” Crawbuck said of the growth of the captive rearing program.

Rooting for recovery

Although she has now released hundreds of island marble butterflies, Shrum still enjoys seeing them in the field.

“I always get excited when I see them. It’s like ‘Go, buddy, go!’” she said after spotting one flying along Pickett’s Lane.

Organizations including the local San Juan Preservation Trust and international Xerces Society for Invertebrate Conservation, as well as individuals such as island resident Susan Vernon, are also rooting for the island marble butterfly to recover.

Vernon said she believes listing the butterfly as endangered was inevitable as the population continued to decline despite habitat being protected and the rearing program having some success.

“It may be down, but it isn’t out. I feel strongly — with our help — it will rebound,” Vernon said.

Xerces Executive Director Scott Hoffman Black said he hopes that’s the case and that the proposal hasn’t come too late.

“I think it is really, really important that we all get together and figure out an emergency-room strategy for this species so we can stabilize it, and a recovery plan so we can recover it and are not stuck in the emergency room forever,” he said.

Xerces twice petitioned the Fish & Wildlife Service to list the island marble butterfly as endangered, first in 2002 and again in 2012. Sixteen years, that listing may be on the horizon.

While endangered southern resident orcas and chinook salmon are considered icons of the Salish Sea, and gray wolves icons of the American West, Shrum said she sees the lesser-known island marble butterfly as an icon of the San Juan Islands and the rare coastal prairie environment in areas of American Camp.

Foley said islanders and all Washingtonians should want to see the butterfly species saved.

“It’s not found anywhere else in the world, and I think we should be taking pride and ownership of it,” she said. “It’s our responsibility to make sure it doesn’t disappear.”

Without Shrum’s long days in the field and lab this time of year, it’s unlikely the few hundred island marble butterflies remaining on San Juan Island would be there.

“This is one of the most endangered animals on the planet,” Hoffman Black said. “The captive rearing program ... that’s how we’re keeping this species afloat, is by rearing them and releasing them. It’s not a good place to be in.”

Those who said the species is worth saving also said that with as few as 200 left, there’s a lot of work ahead to bring the butterflies back from the brink of disappearing.

In comparison, there are about 17 times as many tigers remaining in Asia and about 130 times as many polar bears remaining in the Arctic, according to the Fish & Wildlife Service.

— Reporter Kimberly Cauvel: 360-416-2199, kcauvel@skagitpublishing.com, Twitter: @Kimberly_SVH, Facebook.com/bykimberlycauvel

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