A couple visiting Kailua Beach Park discovered they were sitting atop a turtle nest when hatchlings began emerging from the sand beneath their beach towel in broad daylight.

On Sept. 16, Ben Zitney and Sarah Wagner of California were enjoying a day at the popular shoreline when the baby sea turtles appeared. They moved their towel and watched as approximately 30 baby sea turtles scrambled to the ocean.

It turned out to be a serendipitous discovery.

Researchers from the National Oceanic and Atmospheric Administration confirmed they were olive ridley turtles, which swim throughout the Pacific Ocean but nest primarily along Central American and Indian coastlines, not in Hawaii. NOAA says this is only the sixth olive ridley sea turtle nest ever to be recorded in Hawaii in three decades.

“I was ecstatic when we found the nest,” said NOAA research ecologist Alexander Gaos. “Nesting in the Pacific islands, including the Hawaiian Archipelago, is extremely rare, and I was excited about the extraordinary finding.”

Gaos and his team contacted the couple, who showed them where the site was the next day so they could excavate the nest.

The site was right along the main stretch of the popular beach park, near the vegetation line. Upon digging, the team found empty eggshells and two trapped hatchlings that they were able to release back to the ocean. The nest had contained 72 eggs, 64 of which successfully produced hatchlings, for an overall hatching success rate of 88.9%.

Traditionally, the two species that nest in Hawaii are green sea turtles and hawksbill sea turtles.

Green sea turtle hatchlings are black, and typically hatch in June and July, he said, mostly in the Northwestern Hawaiian Islands. Hawksbill turtle hatchlings are brown and typically hatch over the summer on Molokai and Hawaii island.

The olive ridley hatchlings are gray, and their peak nesting month in other parts of the world is September.

Usually, hatchlings emerge and swim into the ocean at night, but in this case it made sense to go ahead and release the two that were trapped during the day. Zitney and Wagner held the hatchlings before their release, with permission, he said, and had done the right thing by getting in touch with the proper authorities.

Why did the mother ridley choose Kailua Beach Park for her nest?

Gaos said that remains a mystery, but some turtles nest at random locations.

She likely laid her nest during the night, when the beach was mostly empty. Coming out of the ocean, the mother turtle leaves a track behind, but afterward the beach appears flat, and it would have been difficult to locate the nest visually, especially with high foot traffic. The eggs incubate for about a month and a half.

For the next few years, the hatchlings will spend their lives out in the open ocean, feeding on small invertebrates at the ocean’s surface, where they are most at risk of ingesting microplastics or getting entangled in fishing gear.

Few survive to adulthood, according to Gaos, but if they do, they typically return to the beaches where they were born to nest. They do not reach sexual maturity, however, for another 20 to 25 years.

“Every once in a while you get a turtle that roams and will nest at a random area,” said Gaos, who researched how Kauai may have been a steppingstone for turtles colonizing parts of the Eastern Pacific. “For me this is kind of a glimpse of how that process might have occurred. You get the random ridley turtle nest, some babies survive and some come back.”

The other records of olive ridley turtle nests documented in Hawaii include two on Oahu, one on Maui and two on Hawaii island.

Olive ridley turtles are listed as threatened under the U.S. Endangered Species Act, and vulnerable on the International Union for Conservation of Nature’s Red List.

Gaos said if it were not for these two visitors, this rare discovery may never have come to light. He encourages the public to report nesting events as well as marine animal emergencies to NOAA’s statewide hotline at 888-256-9840.