The Oregon silverspot butterfly used to spread its wings across much of the Northwest, from the northern California coast clear up to British Columbia, but the species has struck dire times, with their natural habitat decimated along with the plant they requiring for breeding, the early blue violet.

That's why this summer's release of nearly 450 silverspots reared at the Oregon Zoo in Portland, which culminated with the final release last week on Mount Hebo north of Lincoln City, has been hailed as such a success by zoo officials and conservationists.

"It was the perfect time of year to be out there, right in the middle of the flight season," Karen Lewis, a zoo conservation research associate, said in a statement. "Adult silverspots were flying all around us and flitting across the meadows."

Over the past month, officials from the zoo have been making daily trips to spots along the coast, taking butterfly pupae to the headlands and salt-spray meadows that they instinctively call home. It's at these release sites where the insects complete their metamorphosis, from caterpillar to butterfly, inside mesh pens designed to protect them from predators like voles and white-crowned sparrows.

Those lucky enough to emerge as adult silverspots will need to go about their business quickly, though. The silverspot has an average lifespan of about two weeks, during which they need to mate and find a suitable patch of violets to lay their eggs before they die.

Conservationists are encouraged by their progress along the Oregon coast, though. During last week's release, a newly emerged female was observed fluttering to a nearby flower where she was joined by a male just a few minutes later, "which, you know, is the whole point!" said ecologist Kaegan Scully-Engelmeyer, who manages the weekly releases.

The Oregon Zoo has been a leader in silverspot recovery efforts, with its program dating back to the late 90s. Every year, experts collect female butterflies from Mount Hebo and bring them back to the zoo so they can lay eggs in a conservation lab.

After the eggs hatch into larvae, they are kept safe at the zoo over the winter months so they can grow in the spring and be released back into the coastal meadows in the summer.

"Mount Hebo is where these pupae's parents originally came from," Lewis said. "Essentially, we're putting back what we took and adding quite a few more."

The Oregon silverspot is listed as threatened under the U.S. Endangered Species Act, but despite a drought-caused decline in the flowers they require for breeding on Mount Hebo, Lewis said she was confident that the zoo's efforts were having an impact on the imperiled species.

"The goal of the recovery program is to help each population grow large enough to be self-sustaining," she said in a statement. "If it weren't for this program, three of the five remaining silverspot populations would likely be extinct."

-- Kale Williams

kwilliams@oregonian.com

503-294-4048