Olive ridley sea turtles nest on a California beach for the first time ever recorded

Two olive ridley sea turtles came ashore on Southern California beaches this month and laid eggs, marking the first time any sea turtle species has been recorded nesting naturally on California soil. The first nest appeared September 16 at Seal Beach in Orange County; the second followed September 19 near the Huntington Beach Pier, a few miles down the coast. Researchers say a “super” El Nino warming Pacific waters may be why a species that normally nests thousands of miles south, in Mexico and Central America, chose beaches better known for surfers than sea turtles.

Two turtles, confirmed by their own shell patterns

Scientists distinguished the two nesting events as separate individuals rather than one turtle returning twice, comparing barnacle patterns and shell scales captured in photographs from each encounter. That photo-identification method, standard in sea turtle research, ruled out the simpler explanation and left researchers describing two distinct olive ridleys independently choosing California in the same week.

Neither turtle carried a satellite tag. No one was watching for them.

Jeff Seminoff, a marine ecologist with NOAA’s Southwest Fisheries Science Center, cautioned against assuming warm water alone pulled the turtles north. “They also use an internal compass, sort of an internal GPS in their brain,” Seminoff said. “They’ll respond to wave direction and wavelengths of those prevailing currents. They’ll respond to food availability.” Nailing down which of those cues mattered most this year, he added, is close to impossible after the fact.

A race against cold water before the eggs even hatch

Olive ridley eggs typically take 45 to 60 days to incubate, which places both California clutches on track to hatch well into November, deep into a season the species did not evolve to nest in. Seminoff, describing the risk directly, said the hatchlings’ biggest hurdles would be cold temperatures and the potential for inundation from the extreme high tides that are common this time of year — threats that nesting beaches in Mexico rarely produce this severely, since olive ridleys there typically finish nesting months before autumn storms arrive.

The Aquarium of the Pacific, which coordinates a Southern California Sea Turtle Monitoring program with the U.S. Fish and Wildlife Service and NOAA, said there may be additional turtles that have nested or will nest before the season ends. It is asking beachgoers who spot tracks or nesting activity to call its West Coast Sea Turtle Stranding Hotline rather than approach the animals directly, since disturbing a nesting turtle or an unhatched clutch can do more harm than the cold water already threatens to.

A species already listed as threatened, and endangered in part of its range

Olive ridleys carry federal protection that predates this discovery by nearly five decades. NOAA listed the species as threatened under the Endangered Species Act in 1978, with one exception carved out for the Mexican Pacific coast breeding population, which the agency classifies as endangered outright and subject to stricter fishing and take restrictions. Global numbers have fallen sharply from historic highs even as a few nesting beaches, mostly in Central America and South America’s Atlantic coast, have seen local rebounds.

That patchwork of protections exists because olive ridleys nest in roughly 40 countries, and NOAA’s conservation management for the species spans fishing-gear rules, nesting-beach protections and international agreements written for a Latin American and West African range that never previously included the United States’ Pacific coast north of Mexico. A California nest fits nowhere in that existing framework, which is part of why researchers are treating it as worth tracking closely rather than filing away as a one-time anomaly.

Olive ridleys are among the smallest sea turtles, typically 2 to 2.5 feet long and up to 100 pounds, distinguished by an olive-green, heart-shaped shell with five to nine pairs of scutes along each side. They are best known for arribadas — mass synchronized nestings in which thousands of females come ashore together over a few nights, packing beaches like Mexico’s La Escobilla so densely that later arrivals dig up earlier nests without meaning to, a behavior found nowhere else among sea turtles and never observed anywhere on the U.S. West Coast. Nothing about the two California nests resembled that pattern; both were solitary, unannounced, and caught largely by chance by beachgoers walking the sand rather than researchers stationed there to look for them.

Jeff Flocken, president and CEO of the Aquarium of the Pacific, framed the nests as a signal that conservation planning needs to catch up to shifting animal behavior rather than treat it as a one-off curiosity. “As animals adapt in unexpected ways to changes in their natural world, humans will need to adapt and make space to ensure endangered and threatened species are given a fighting chance,” Flocken said.

The aquarium opened a dedicated sea turtle rehabilitation facility, with a 4,000-gallon pool, in January 2026, months before either nest was found. It currently houses two resident olive ridleys, Theo and Lou, animals that arrived through the West Coast’s existing stranding network rather than as wild nesters. Whether the hatchlings from Seal Beach and Huntington Beach survive the colder weeks ahead will be the first real test of whether a warming Pacific can turn an odd sighting into a recurring one.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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