The Ostional Wildlife Refuge in Costa Rica was created in 1984 to protect one of the world’s most important nesting sites of the Olive Ridley Sea Turtle. It was a destination I had been interested in visiting since 2017 as the beaches of Ostional are the location of a rarely seen biological wonder – an Arribadas.
It’s hard to describe the supernatural feeling of standing on this beach, watching turtles arrive from thousands of miles away to lay their eggs and then vanish back into the sea – never looking back.
In rainy season, the week before the new moon, hundreds – and sometimes hundreds of thousands of sea turtles, come to one specific mile of beach at Ostional to lay their eggs into the black, volcanic sand. Only Olive Ridley Turtles and their close relatives, Kemp’s Sea Turtles, synchronize their nesting in mass emergences or “Arribadas”, the Spanish word for arrivals.
We were lucky enough to visit twice. Once under the cloak of night armed with red lights, where we witnessed the entire nesting process and again two days later at daybreak, as shown in the featured photo above, to witness an actual Arribadas.
Some days, and sometimes even weeks before a mass nesting, a “flotilla” of turtles, congregates closely just offshore. After an unknown amount of time and prompted by some secret signal, the “Arribada” will begin. At first, a few dozen turtles will come out on the beach, followed by a steady stream for the next three to seven days.
We were lucky enough to witness this on a smaller, more accessible scale and from the shore, you could see heads bobbing up and down in the surf, just offshore, waiting their turn.
Olive Ridley Turtles nest at Ostional year round, but peak time is during rainy season. From August through December, Arribadas occur regularly once, sometimes even twice a month, and the numbers of nesting females are in the range of hundreds of thousands as opposed to simply thousands during the dry season. Usually the Arribadas occur during the darkest nights: a few days before the new moon, when the majority of turtles arrives between 8 pm and 4 am. We started out at 5:30 am to catch the stragglers coming up to lay their eggs.
The largest ever recorded took place in November 1995 when a calculated 500,000 females came ashore.
Visitors are only allowed onto the beach with a certified Guide. We were fortunate enough to visit with Jairos Quiros, the Director of the Ostional Tour Guide Association.
The local community in Ostional, Costa Rica, collects Olive Ridley turtle eggs as part of a unique, government sanctioned and regulated conservation project that started in 1987. This practice allows residents to harvest eggs during the first 36 hours of a mass nesting event (arribada) for both personal consumption and commercial sale.
There are several reasons for this practice.
“Doomed” Eggs Management: The primary ecological rationale is that during mass nesting events, thousands of turtles arrive simultaneously and dig up the eggs of those that nested on previous nights, or even an hour earlier, as we witnessed. The eggs collected in the first 36 hours are considered “doomed” because they would likely be destroyed by subsequent turtles or rot, spreading bacteria that infects other nests.
Improving Hatching Success: By removing the eggs laid on the first night, the community helps reduce the “Giant Omelette” effect—where broken eggs foul the beach. This actually improves the survival rate of the remaining eggs (laid later in the week) by reducing bacterial contamination. It was obvious during our visitors how bad an isue this could become as hundred, if not thousands of eggs were scattered about the surface of the beach, being gobbled up by vultures, storks and other opportunistic feeders.
Economic Sustainability and Livelihood: The sale of these eggs provides a vital source of income for the local community of Ostional. This helps to alleviate poverty and provides an alternative to engaging in illegal poaching.
Community-Based Conservation: By granting legal access to the eggs, the government incentivizes the locals to protect the beach, the nesting adults, and the hatchlings from poachers and predators. The community takes ownership of the protection of the refuge.
It’s a little sad to watch as the eggs are being collected sometimes before the mother even reaches the open ocean, but the conservationist in me recognizes the necessity.
I’m glad I got to see this with Yim. It was certainly a once in a lifetime experience.
This really showed me how Costa Rica values protecting its environment over just developing land. Programs like this don’t just save endangered sea turtles—they also support the local economy. Eco-tourism brings visitors, creates jobs, and encourages sustainable practices, so protecting nature and supporting people go hand in hand.
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