Hundreds of endangered butterflies slated to be released along California coast

Hundreds of rare, blazing orange butterflies are slated to be released in Northern California over the next two years, marking a victory for conservationists working tirelessly to restore them across the region.

In 2023, the Mendocino Land Trust received a $1.5 million grant to restore critical habitat for the Behren’s silverspot butterfly, an endangered butterfly endemic to California’s lush Mendocino coastline. So far, it’s only been discovered along the coast from Salt Point Park in Sonoma County to the Mendocino Headlands, Anna Bride, the land trust’s stewardship project manager, told SFGATE, and it faces a slew of existential threats ranging from coastal development to climate change.

Nectar plants and native grasses used to flourish in the region, Bride said, but now, habitat degradation and commercial developments are pushing the rare butterfly to extinction. As grazing farmland grew, monocrops like European beach grass and rattlesnake grass proliferated, decimating the notoriously picky butterfly’s main food source, the early blue violet.

“It’s this tiny little flower and it’s the only leaf that this caterpillar eats,” Bride said.

The new grant funding will go toward planting at least 30,000 of these bright purple flowers and restoring the butterfly population over the next four years, she explained. Last year, 180 specimens were unleashed into the wild. Project partners aim to release up to 600 of them by 2026, Christine Damiani, a Marine Land Trust project partner and entomologist at Eureka’s Sequoia Park Zoo, told SFGATE.

Bride kept project locations vague, explaining that poachers may try to kill these rare insects for profit. In 1995, the U.S. Fish and Wildlife Service famously uncovered a massive butterfly poaching operation throughout Death Valley and multiple national parks and wildlife refuges, according to the National Park Service website. Three men were prosecuted for illegally capturing thousands of rare butterflies, 14 species of which were endangered.

Now, members of the Bureau of Land Management, the U.S. Fish and Wildlife Service, the Sonoma-Mendocino Coast District of California State Parks and the Sequoia Park Zoo are involved at every stage of the Behren’s silverspot life cycle thanks to the recent funding.

For the past three years, Damiani has been carefully raising the caterpillars in a lab, which increases their chances of survival. “In the wild, caterpillars face high mortality risk from predation, disease, trampling, pesticides, and extreme environmental events,” she told SFGATE.

Each August, she begins the process by capturing Behren’s silverspot butterflies in Mendocino and taking them to the zoo, where they undergo a monthslong metamorphosis. After collecting their eggs, she puts them in a refrigeration unit over the winter, where they enter a dormant state known as diapause.

Once they awaken from their slumber, they’re transferred back to the lab and fed a gourmet diet of early blue violet leaves — thousands of which are grown and harvested at the zoo each week, she said. Then when summer rolls around, the pupae are brought back to the Mendocino coast and delicately placed in mesh enclosures, where they finally become butterflies and get released into the wild.

According to Damiani’s Facebook page, there are 1,412 caterpillars in captivity, meaning her team is poised for a busy spring season this year, though not all of those caterpillars will survive.

Damiani said that there have been only 92 Behren’s silverspot sightings over the course of 15 years, but Bride and her team are hopeful they’ll discover more when they start surveying the coast this summer. For now, she’s optimistic that the new grant funding will bolster conservation efforts and save them from extinction.

“I think it’ll make quite a big difference on the impact that we’re able to make,” she wrote.