San Francisco Chronicle

Unique Bay Area serpent is a survivor

- Reach Peter Hartlaub: phartlaub@sfchronicl­; Twitter: @PeterHartl­aub

As a research biologist with the U.S. Geological Survey, it’s been Brian Halstead’s job for years to observe the San Francisco garter snake. And he’s constantly startled by its beauty.

It has an orange-red head, turquoise chin and both colors running in stripes, along with white, across the length of its lean black body. The reptile has the shine of a tire recently sprayed with Armor All, and the bold color choices of a contestant on “RuPaul’s Drag Race.”

“It’s a snake,” Halstead says, “that even somebody who doesn’t like snakes can love.”

The San Francisco garter snake is both a stunner and a survivor, its habitat shrunk to alarming extremes by encroachin­g urban sprawl. The snake lives only in the Bay Area, its highest profile home flanked by a freeway overpass, PG&E transforme­rs and the San Francisco Internatio­nal Airport. It has been name-checked by Ronald Reagan. It’s been on a stamp.

So why don’t more people know it exists?

The San Francisco garter snake has long since been driven out of the city that shares its name. By the time the snake — which loves to hunt in the vegetation near lakes and marshes — was recognized on the federal endangered species list in 1967 and state list in 1971, it had been almost entirely eradicated by San Francisco’s rapid growth.

The reptile was first mentioned in The Chronicle in 1972, when a UC Berkeley student fought to save its habitat near Lake Merced from a 200-townhouse developmen­t. The board, including thenSuperv­isor Dianne Feinstein, voted 9-2 to build without considerat­ions.

“You are aware, I assume, that the San Francisco garter snake, unique in the world, is an endangered species (when you garter go, you garter go),” Chronicle columnist Herb Caen quipped.

But the jokes soon ended, and concern for the species’ future soared. A year later, Reagan signed wildlife legislatio­n that imposed stiffer penalties on exotic animal sellers who were trapping the attractive snake. By the 1990s fines rose to $1,500 per snake, and wildlife officials were working more aggressive­ly to preserve existing habitats and monitor the species’ numbers.

Now there’s a Snake Recovery Action Plan to protect the garter snake and California red-legged frog at the airport site, and groups including the U.S. Fish and Wildlife Service, California Department of Fish and Wildlife and the San Francisco Internatio­nal Airport are working for the snake’s survival.

I had never heard of the San Francisco garter snake until it was nominated by preservati­onists for our Total SF podcast Official Animal of San Francisco contest. It advanced to the second round; beating out well-known city residents including seagulls and penguins. But most reporting is out of date — The Chronicle last wrote a story about the snakes in 2005.

So I called Halstead, who confirmed that the snake still roams in several areas on the San Mateo County Peninsula, under protection by federal, state and regional biologists, who are constantly monitoring both the numbers and genetic health of the animals.

“It’s one of the most beautiful snakes in the world, and it happens to be restricted to one of the most urban areas in the U.S.,” Halstead said. “So that obviously brings with it some threats.”

He’s coy about exactly where it lives. (“I don’t think I can reveal the actual location,” he says after talking about one thriving habitat. “It’s mid-Peninsula.”)

The snake’s homes over the last half century include Mori Point in Pacifica, Año Nuevo State Park south of Pescadero and that spot by SFO. The snake’s dibs on the runway-adjacent land forced Caltrans to redesign a freeway offramp to the airport. The area is surrounded by locked gates now, and biologists still monitor it.

Exact numbers regionwide aren’t available, but estimates for the SFO habitat have been fairly steady over the last 15 years, ranging from 1,269 to 1,465 snakes, with 1,310 at the most recent survey in 2017. There are no wild population­s of San Francisco garter snakes outside the Bay Area.

The snakes grow up to 3 feet in length, with babies the size of earthworms. They eat frogs, insects and other small prey. Halstead talks about a recent rangewide sampling of snakes. Shrinking population­s are always a worry — a 1993 search at the SFO site counted only 79 snakes — and federal officials have considered aggressive interventi­ons, such as the removal of bullfrogs, which compete with San Francisco garter snakes for food.

But genetic health has been an increasing concern in recent years. A 2017 survey revealed a lower diversity of the snake’s genetic makeup.

“That suggests that the population­s are more isolated than they used to be, and that isolation is causing degradatio­n in the genetic diversity of the snakes,” he said. “So that in the long term, it’s definitely a cause for concern.”

Interventi­on is possible in the future — either establishi­ng new habitats or exchanging snakes from unconnecte­d habitats to strengthen the bloodlines. For now, biologists want to bring attention to the snake, in part so people leave it alone.

Halstead notes that while the snake may have been unknown to me, nature-lovers know exactly what’s out there. San Francisco Zoo officials confirm they’re currently nursing one back to health. (It’s not on display.) The Recreation and Park Department added a San Francisco garter snake tile mosaic to Louis Sutter playground in McLaren Park.

And while it’s not the official position of the USGS, Halstead said the San Francisco garter snake has his “Official Animal” vote.

“This is completely a personal thing, but it would almost be a shame to not have that as the city animal,” he said. “To have something so striking and endangered that only occurs on the San Francisco Peninsula. It’s just a really unique situation.”

 ?? Paul Chinn/The Chronicle 2005 ?? A San Francisco garter snake gets attention in 2005 at the San Francisco Zoo’s Animal Resource Center.
Paul Chinn/The Chronicle 2005 A San Francisco garter snake gets attention in 2005 at the San Francisco Zoo’s Animal Resource Center.

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