Sunday, December 4, 2022
Dec. 4, 2022

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Will this rare butterfly found only on San Juan Island go extinct?


SAN JUAN ISLAND — The chrysalises are delicately perched on twigs, safeguarded by little more than plastic food containers stacked on shelves inside the captive rearing lab.

Barely more than a hundred of the dormant insects are the latest generation of a dwindling kind.

Next spring they will emerge and sprout wings as island marble butterflies, an endangered species found in critically low numbers and only at the national park here.

For the past decade, park researchers have used the rearing lab, in an unassuming cabin near the island’s southern tip, to raise and release on average hundreds of the butterflies.

“What if something happens to this building?” said Sara Dolan, the park’s resources stewardship program manager, as she stood outside the lab with a pair of staffers. The trio manages the lab. “It’s very challenging for us to be the stewards of this species. It’s a heavy weight.”

This butterfly went unseen for 90 years, only to resurface on San Juan and Lopez islands in 1998. Since then, they’ve suffered extensive habitat and population loss.

It’s unknown exactly how many exist in the wild.

But there’s hope the butterfly could rebound thanks to community efforts to expand habitat. Promising new research combining photography and advanced software to better identify individual butterflies could further unlock the secrets of a species facing a fragile future.

Shifting habitat

The island marble butterfly, a subspecies of the more common large marble butterfly, begins life by hatching from eggs in the spring. After a month or so eating the host plant on which they were laid, the caterpillars undergo metamorphosis and spend the next 10 to 12 months in a chrysalis. After emerging, the butterflies have a wingspan of almost 2 inches and a life span of 6 to 9 days.

The vibrant mix of green and white in the fluffy, marbled patterning on the underside of their wings has made the butterflies a recognizable but rarefied encounter for island residents.

About 80 to 90% of those released from the rearing lab survive, while only a fraction — as low as 2% — reach adulthood in the wild.

Researchers had been pushing for more than 20 years for the butterfly to be protected under the Endangered Species Act. It was finally listed in 2020, leading the federal government to designate more than 800 acres as critical habitat, mostly within the park.

Still, its chances of survival since then have only become more dire.

Until 2007, the island marble butterfly could be found at about 25 locations on Lopez and San Juan islands.

Now the species only is found at American Camp at the San Juan Island National Historical Park, a 2,100-acre property operated by the National Park Service.

Development, construction and other human activity is thought to be the largest cause of habitat decline since then, but nonnative deer, rabbits, wasps, snails and plants also pose a significant threat.

The butterfly’s habitat has been largely influenced by San Juan Island’s colonial past.

The Hudson’s Bay Co. in 1853 created a sheep farm, the island’s first nonnative settlement following millennia of Indigenous stewardship. The sheep farm would eventually become part of American Camp.

The British wrestled with Americans over control of the island, a dispute that almost triggered a war in 1859 when an American settler shot a pig owned by Hudson’s Bay.

Now, the island is home to almost 6,900 residents. Tourism has been climbing dramatically since it saw more than a quarter-million visitors in 2019, 425,000 in 2020 and 750,000 in 2021. The park expects this year’s visitors to reach 800,000.

More traffic is good for the island’s economy, but not necessarily for wildlife.

Earlier this year, someone in an off-road vehicle drove right over the butterfly’s prairie habitat. On a different occasion, someone stole large stretches of wood fencing on park lands.

Separately, just a few miles north in Friday Harbor, a man was charged in May with arson after he allegedly burned down several buildings and businesses, causing millions in damages.

Such dangers pose a logistical nightmare for Dolan and her team, and a serious threat to the butterflies.

At the rearing lab, researchers joked that it’s like keeping all your data on a single, faulty flash drive.

“It’s a super unique butterfly,” said Amy Lambert, an expert on the island marble butterfly and professor at the University of Washington, Bothell. “The study of it is complex.”

While the species is extremely limited, both in number and available habitat, efforts to help the butterflies spread elsewhere on the island — namely at a private homestead adjacent to American Camp — are ongoing. Still, without detailed knowledge of the butterfly and its life cycle, conservation and recovery will remain a vexing proposition.

“As a researcher, and someone who has worked with this animal for so long, I can’t wait for the day that we can take it off life support.” Lambert said. “How do we know when we can step back from captive rearing?”

New tool

Scientists often catch and release insects to study their behavior and physiology. But the technique, also called “destructive sampling,” is a risky method.

To understand the rare species, and potentially secure its existence, researchers need a more delicate approach.

In September, biologist Jenny Shrum was awarded a $50,000 research grant to develop the use of photo identification to help provide an accurate count of the island marble butterfly population. The same technology is often used to identify whales, bears and cattle. But butterflies and other “tiny, flying and ephemeral species” are usually faster, smaller and spend most of their time in dizzying clusters that make it extremely difficult to count or measure movement, according to the U.S. Fish and Wildlife Service.

The ability to pair photography with advanced software, so that an individual butterfly can be photographed, its wings virtually flattened or flipped, if need be, to be identified, cataloged, matched and compared, could be a game changer.

“Butterflies are an inherently difficult animal to study because they’re so fragile and, in this case, because they’re also so rare,” Shrum said.

During a trip into the field in 2020, she was able to determine that butterflies raised in the lab were mating and laying eggs in the wild, a new discovery.

Shrum hopes to use the grant money to develop this technique and find partners with shared interests. Even as researchers work to improve and expand their habitat, basic questions shroud the butterfly.

It’s unknown exactly how many are born in the wild each year, or whether that population is growing or shrinking. The fundamental fear is the possibility that, without the captive rearing lab, the species would disappear.

“All of this matters because we’re trying to encourage people to develop habitat on private land across the island,” Shrum said. Currently there is no harmless or flawless way to count butterflies, but she believes that could change soon. Researchers don’t necessarily know how habitats need to be spaced out, or what corridors the butterflies need to travel even short distances.

“It just seems like this incredible tool that could potentially answer some really important questions at a crucial time.”

Stewards’ toil

During the spring, when the island begins to warm, the butterflies skip between host plants in three places inside the park — a grassy prairie, a trio of lagoons and a dune.

Each host plant is more or less unique to each niche. Not only that, two of the plants are nonnative, making habitat “restoration” a bit of an ecological quandary.

The field mustard, a 15- to 30-inch-tall nonnative plant with vibrant, yellow flowers, is mostly found in the park’s prairies. Tumble mustard is found predominantly in the dunes, while the Virginia pepperweed , a native plant, is found around the lagoons.

Twice a year, park staff spend hours preparing the prairie habitat to give the butterfly’s host plant a better chance of survival. Earlier this month, a stretch of sunlight on the island warmed Claire Crawbuck and Trent Lieber as they raked the top layer of invasive grass and churned the soil below.

Lieber, the national park’s natural resource specialist, draws cautious optimism from the butterfly’s resilience.

“No one even knew they existed and they still managed to reappear,” Lieber said.

Crawbuck, a 28-year-old biological science technician, grew up on the island. She never expected her research to be focused on the survival of a single butterfly species.

Things have obviously changed since then. Now, she said, “they’re our babies.”