A river otter showed up on a trail camera at Cloverdale Ranch Open Space Preserve near Pescadero this year, and researchers say it is the first documented sighting of the species on the San Mateo Coast since the 1800s. The animal was photographed at night on three separate occasions — July 15, August 31 and September 2 — among more than 5,100 acres of coastal grasslands, forest and streams south of Half Moon Bay.
The discovery was made by Ken Hickman, an amateur naturalist from San Carlos who works with the Midpeninsula Regional Open Space District and other agencies, according to The Mercury News. Hickman set up ten trail cameras throughout the preserve and checks them about once a month; besides the otter, his cameras have also captured beavers, mountain lions, striped skunks, spotted skunks, coyotes, gray foxes, bobcats, opossums, raccoons and deer. Biologists have since verified that the animal photographed is indeed a river otter, per the same report.
As coastsidebuzz.com reported, Hickman said river otters haven’t been known to occur on the San Mateo Coast since the 1800s, when the 19th-century fur trade nearly wiped them out. The Mercury News notes that river otter populations statewide declined through that era because of hunting for their dense fur, along with development and toxic chemicals that degraded their habitat.
A Newly Protected Stretch of Coastal Watershed
Cloverdale Ranch itself has a long conservation backstory. The Peninsula Open Space Trust purchased the land in the late 1990s specifically to block a luxury home development on the property, which had formerly operated as a farm near the Pigeon Point Lighthouse, according to The Mercury News. The Midpeninsula Regional Open Space District acquired the preserve in 2023, and most of its acreage is not yet open to the public.
The land is ecologically significant well beyond this one sighting. According to the Peninsula Open Space Trust, the 5,100-acre transfer included 15 miles of streams across three critical watersheds that support rare, threatened and endangered species, and the preserve connects to more than 31,000 acres of surrounding parkland, forming wildlife corridors. The Mercury News reports that creeks near Cloverdale Ranch — including Pescadero Creek, Butano Creek and Gazos Creek — offer exactly the kind of inland waterways river otters favor.
A Decades-Long Comeback Across the Bay Area
The Pescadero find fits into a much larger pattern of recovery. River otters have made a comeback across Northern California and are increasingly sighted along San Francisco Bay, the Sacramento-San Joaquin Delta, Marin County and Sonoma County, The Mercury News reports, though they are not listed as an endangered species. Matt Sharp Chaney told the outlet that the otters’ return to places they had been absent from for many years is exciting and shows resilience, while Megan Isadore said river otters are doing well currently.
Environmental laws dating to the 1970s that supported cleaner air and water helped drive that recovery, according to the same Mercury News report. A 2015 study in the Northwestern Naturalist tallied 1,374 individual otter sightings across eight of nine San Francisco Bay Area counties in 2012 and 2013 alone, and concluded the species was recovering and likely expanding into the southern reaches of the region, including first-in-decades sightings in Alameda, San Francisco and Santa Clara counties.
Otters have still been slow to expand their range down the coast south of the Golden Gate Bridge, per The Mercury News. KQED has reported that otters have been found in nearly every Bay Area county except San Mateo, and the River Otter Ecology Project says its Otter Spotter program has logged more than 2,300 Bay Area sightings since 2012 without a confirmed record in San Mateo County. Statewide, the River Otter Ecology Project has documented more than 6,500 sightings since 2012, and researchers say otters are expanding from the North Bay and Delta into the wider Bay Area, The Mercury News notes.
Sutro Sam and the San Francisco Precedent
The best-known recent otter appearance on the ocean side of the Peninsula came in 2012, when a solitary otter nicknamed Sutro Sam took up residence at San Francisco’s Sutro Baths, according to coastsidebuzz.com. KQED similarly reported that Sutro Sam showed up at Lands End in 2012 and stayed for nearly six months. The Mercury News reports the animal was simply named Sutro Sam at the time.
Elsewhere around the Bay, otters have been spotted in marshes and wetlands near Redwood City, Newark, Alameda and other parts of San Francisco Bay, and along Coyote Creek south of San Jose, per The Mercury News. Researchers studying wetlands near Martinez found river otters had been regularly sighted there since at least 2005, including a group of nine seen in Moorhen Marsh in 2011, according to a River Otter Ecology Project study of that site.
How Did It Get There, and What Comes Next
Nobody yet knows how the Cloverdale Ranch otter arrived. Megan Isadore suggested to The Mercury News that the animal may have swum down from farther north along the ocean, or traveled up from the Bay through creeks and across the Santa Cruz Mountains. Isadore said she plans to raise funding for surveys along the San Mateo County coast that would look for footprints, scat and other evidence of additional otters, and researchers could also use environmental DNA testing in local creeks to identify animals from shed genetic material, the paper reports.
River otters typically live eight to 15 years in the wild and can reach 20 years or more in captivity, feeding on fish, frogs, salamanders, turtles, small birds and mice, according to The Mercury News. Females can have litters of up to six pups. Isadore urged anyone who spots a wild river otter to photograph it and report the sighting through her organization’s website, the River Otter Ecology Project.
