River Otters Rediscovered
Published October 1, 2026
Recently, while reviewing wildlife cameras, independent researcher and Midpen partner Ken Hickman spotted something unexpected from a wildlife camera in Cloverdale Ranch Open Space Preserve: A river otter.
"Checking wildlife cameras can be like Christmas, but river otters haven't been known to occur on the San Mateo Coast since the 1800s," explained researcher Ken Hickman. "So I knew Midpen and State Parks biologists would be as surprised and interested as I was to see the photos."
Historically, North American river otters (Lontra canadensis) ranged along the California coast as far south as Santa Barbara. However, the 19th-century fur trade nearly wiped them out, leaving severe gaps across their historic habitat.
In modern decades, their presence is much more common north of the Golden Gate in Marin and northern Alameda and Contra Costa counties. Some sightings have been made in San Mateo and Santa Clara counties, primarily in the bay wetlands. Along the ocean-facing side of the San Francisco Peninsula, the only notable sighting in recent memory was "Sutro Sam," a solitary river otter who famously took up temporary residence in San Francisco’s Sutro Baths in 2012.
“River otters can serve as vital bioindicators,” said Midpen biologist Matt Sharp Chaney. “River otters thrive in clean water and areas with abundant food supplies, meaning they can only move into aquatic systems capable of supporting complex food webs. Their presence in Cloverdale Ranch and the reclamation of their historic range offers evidence of the species recovery post fur-trade and a robust ecosystem, one healthy enough to harbor key indicator prey like coho salmon and steelhead trout.”