Ecologists return butterflies to S.F.
California ringlet has not been encountered in Presidio since ’07
“To walk in a California grassland and not see a ringlet flying around, it seems like something is off. They’re such a California grassland species.”
Jon Young, Presidio Trust wildlife ecologist
A group of ecologists, volunteers and a lepidopterist trudged up a Marin hillside in the warm sun last week, nets and coolers in hand. They scoured the grassland for a small butterfly with silvergray wings and the occasional pop of copperorange, a color scheme that helps it blend into the yellowing grasses and spring poppies.
They were collecting California ringlet butterflies to relocate to the Presidio of San Francisco, where they haven’t been seen since 2007. While it’s not the prettiest butterfly, nor the rarest, wildlife experts say the return of the fuzzy gray insect to the Presidio is a vital part of the national park’s slow transformation back into something approaching its native self.
“What it represents is an effort that we in the Presidio are taking to manage the landscape in a new way,” said Lewis Stringer, associate director of natural resources at the Presidio Trust, which manages the 1,491acre park along with the National Park Service. “There’s a recognition that with a loss of biodiversity you have to keep the common things common.”
After gingerly collecting five male and five pregnant female California ringlets in the Marin Headlands, Presidio Trust ecologists drove them across the Golden Gate Bridge and released them near Inspiration Point, an area where the Presidio Trust has been restoring serpentine grassland, the butterflies’ native habitat, for many years. The team will continue to capture and release small numbers of butterflies until they reach 100. Then they’ll repeat that each year for two more years to reestablish a population.
“There are some badger holes to avoid. It’s not just fun and games.”
Ecologist Jon Young
“Releasing them is always very satisfying and exciting,” said Presidio Trust wildlife ecologist Jon Young, who is in charge of collecting the insects. “What’s really satisfying is seeing a new generation rear on its own.”
The Presidio Trust was established 25 years ago, two years after the National Park Service took over the land from U.S. Army. Since then, trust and NPS staff and volunteers have restored and replanted grasslands, coastal bluffs, oak woodlands and tidal marshes that had been paved over with asphalt or crowded out by nonnative trees and weeds. They also reintroduced native insects and animals, including several endangered species.
They include the Western pond turtle, which recently showed a sign of a healthy population when ecologists found a baby last month for the first time since they reintroduced it to Mountain Lake in 2015, and the variable checkerspot butterfly, which now flutters all over the park after being reintroduced in 2017. Coyotes showed up on their own, as did silver digger bees, which hadn’t been seen in Presidio in significant numbers in a century.
An important reason to return native animals and plants is that complex ecosystems are more resilient to climate change, Young said. Another is just to reestablish normalcy.
“To walk in a California grassland and not see a ringlet flying around, it seems like something is off,” Young said. “They’re such a California grassland species.”
Even though the grasslands at Inspiration Point have been restored, the ringlets won’t come back on their own because they can’t fly very far — not across the Golden Gate nor from nearby San Bruno Mountain nor Candlestick Point, where there are lots of them.
“In an area where there’s a lot of grass, you’re probably going to find ringlets,” Young said.
The challenge in collecting them, though, is that ringlets don’t flit showily from flower to flower, especially the pregnant females, who tend to hunker down in the grass. That was the population Young targeted in the Marin Headlands, hoping they would lay their eggs immediately upon their arrival in the Presidio.
Young and lepidopterist Liam O’Brien, along with other staff and volunteers, also collected some males, which are far easier to find because they tend to be on the move. To coax the females out, the collectors dragged their butterfly nets slowly along the ground until one jumped up and could be caught safely. It’s a painstaking process.
“There’s a lot of running around — there are some badger holes to avoid. It’s not just fun and games,” Young said.
After catching the butterflies, the experts check their gender. The pregnant ones — that’s basically all females this time of year — can be distinguished by their slightly broader abdomens, each filled with a dozen to two dozen eggs. The collection crew places each butterfly in a clear plastic deli container, and the females go into a cooler with a bit of ice to keep them calm. That way, they don’t burn as much energy and damage their wings during transit, Young said.
After collecting the quota of five females and five males, the team headed back to the Presidio’s Inspiration Point. Once the group opened the containers, the butterflies flew out and found new spots in the grass to settle.
Some would lay their eggs right away. The females have only a few more weeks to live, if they avoid being eaten by predators. The hope is that the butterflies born of their eggs reproduce, Young said.
The Presidio Trust hopes to launch more projects like this, such as bringing back populations of California quail and redlegged frog.
“The goal is to demonstrate that these parklands can be really genuine wild places that support the kinds of species that used to be here and that are not longer here,” Stringer said. “With the crisis of biodiversity loss we’re seeing across the world, we have to be engaged this way. It’s not that hard to do.”