Blue butterflies back in San Francisco, after Xerces extinction

Yahoo

25-03-2025

The Brief
Cal Academy of Sciences and The Presidio join conservation efforts to bring blue butterflies back to San Francisco coast.
Genetic sequencing links Silvery blue butterflies to extinct Xerces blue.
From March through May 2025 scientists hope to see new generation of silvery blue butterflies emerge after introduction to new Presidio habitat.
OAKLAND, Calif. - In the San Francisco Bay Area, the Xerces blue butterfly went extinct along the San Francisco coast some 80 years ago, but now the California Academy of Sciences and the Presidio Trust have identified a similar species of blue butterfly and are trying to introduce it back to the region where the Xerces blue butterfly was once so common.
Durrell Kapan, a senior research fellow at the California Academy of Sciences, is part of that effort and spoke with Jana Katsuyama on the Four to explain the effort:
Most butterflies…most organisms that go extinct are due to habitat loss. So California, after the gold rush, especially San Francisco, saw a lot of development. And so most people don't know that most of San Francisco was awash with dunes. Pretty much the first two-thirds away from the ocean was all dunes. That was a perfect habitat for a butterfly, a little blue butterfly, that flew, feeding on a specific host plant called deer weed. It's a pea family plant with an orange and red flower. Those plants didn't have the dunes to live in, and the butterflies didn't have the plants or the dunes, and so they went extinct.
Now you have identified butterflies that are very closely related: the Silvery Blue butterflies that are in Monterey County. How did you use genetic sequencing to identify the connection between these two species?
I'm super fortunate to have a great team here at the California Academy of Sciences. We were able to extract DNA non-destructively from a leg of one of the specimens of silvery blues that we had in the collection. And so we were able to compare the DNA from a bunch of Xerces and a bunch of silvery blue butterflies, which we hypothesized to be the closest relative, to sort of narrow down which ones were closer. And I'm super happy to be part of this team at the Cal Academy that can do that kind of work. So that's the basic story.
How were you able to restore that habitat that you said was lost, and introduce dozens of the silvery blue butterflies to San Francisco's coastline? Why is it important to bring butterflies back?
That was one year ago…about a year ago, in April. But the work on this habitat has been going on for a long time. The Presidio and the National Park Service have been restoring habitat among other groups across the city since the mid-90s. It's part of their mandated work, and only when the restoration is kind of mostly ready to go would we be interested in bringing back species that couldn't migrate there on their own, like, in this case, the silvery blue butterfly as a stand in for the extinct Xerces blue butterfly.
Why is it important to have that stand in, if you will, to be in the ecosystem, in the habitat there?
Well, the basic idea is that the butterfly presents like a single organism that does a job. The job is to feed on plants. As adults, they pollinate certain plants, they may have an interaction with ants, and they'll be prey. But that job, in this case, for the Xerces blues, is actually outsized, because that's a very, it's an inspirational butterfly. The Xerces was the first known invertebrate to go extinct in North America. It became the namesake of the Xerces Society for Invertebrate Conservation. So working on putting a blue butterfly back where Xerces used to fly is extremely inspiring for conservationists and communities, community members and others.
You mentioned that this was actually released last year. How are you tracking it? Or are you tracking the success of this?
Yeah, we're, we're tracking it pretty much since late February. It's a very small chance that eggs that were laid last spring could be close to becoming pupa into adults as early as mid-March and as late as May. So we're going out there every single sunny day to look.
That must be so exciting to be able to see that in action after all of that hard work before. Everybody thinks of butterflies as being so beautiful, but in a global sense, why is it so important to have species preservation and for all of us as individuals to try and support those populations?
So monarchs are another species which is really interesting. They're migratory, so they sample different habitats. Like the wintering habitat for the Eastern monarch is in Mexico…they increased…they doubled since last year, which was a very low number. It's like not so low, but still a low number.
They also have a monarch population in California, and they have been doing okay, and then they started to go down in 2020, to a very low number, back up to the hundreds of thousands, and then just this last year, they're down again in the low numbers. So those kind of butterflies are like canaries in the coal mine, because they sample different habitats for wintering, where they stay in these eucalyptus groves…Then in the spring, they need milkweed to migrate towards their summer habitats. They need milkweed in their summer habitats.
And then there's a supergeneration that migrates down to Mexico or onto coastal California for the winter. Those are two separate populations. They're kind of out of sync. So the monarch news is good for East right now. It's kind of dire for the west right now. But those butterflies themselves are like canaries in a coal mine, like I said. They're pollinators, they're prey, and they're amazing herbivores. So, without butterflies and other insects that eat plants, plants would be growing out of control.
A conversation with Durrell Kapan, senior research fellow at the California Academy of Sciences.
Jana Katsuyama is a reporter for KTVU. Email Jana at [e-mail]. Call her at 510-326-5529. Or follow her on Twitter @JanaKTVU and read her other reports on her bio page.