Ostional: the turtles at the end of the corridor

A short drive north of Nosara, olive ridley sea turtles come ashore in numbers that are difficult to believe until you have stood in them. The event is called an arribada — an arrival — and Ostional hosts one of the largest on earth. In the rainy months, nesting females can run into the hundreds of thousands.

The refuge that protects them is the coastal end of the biological corridor now being assembled up the Nosara River valley.

What is an arribada?

A synchronised mass nesting. Rather than coming ashore alone, olive ridleys gather offshore and then land together over several consecutive nights, in such density that the beach becomes difficult to walk without stepping between turtles.

Each event lasts roughly three to seven days. The turtles come in from sunset until around six the following morning.

When do they happen?

Regularly, and more or less monthly — sometimes twice a month — with the peak during the rainy season from August to December. Dry-season arribadas still occur but with nesting females in the tens of thousands rather than the hundreds of thousands.

They tend to fall on the darkest nights, in the days just before a new moon. The largest recorded event at Ostional brought around 500,000 females ashore in November 1995.

October, in other words, sits in the middle of the best months.

What is the Ostional National Wildlife Refuge?

Established in 1984, it protects roughly 15 kilometres of shoreline — a narrow 200-metre strand of beach, extending inland through estuaries and mangrove, plus a three-mile maritime zone offshore. Playa Guiones, about ten minutes from this estate, falls within that stretch.

The refuge exists because the nesting beach is a globally significant one, and because a beach alone does not protect a species that also needs the estuaries, the mangroves and the water beyond it.

Why is egg harvesting legal here?

Because at Ostional it is, unusually, defensible — and it is the reason the community protects the turtles rather than poaching them.

In an arribada of this density, later-nesting females dig up and destroy eggs laid in the first days. Those clutches are lost regardless. Since 1987 the government has permitted the Ostional community to harvest eggs during the first three days of an arribada. In exchange, residents protect the nesting turtles, clear debris from the beach, and patrol day and night against poachers.

It is one of the few legal sea-turtle egg harvests in the world, and it has held for nearly four decades.

How do you see one responsibly?

Go with a local guide from the community, at night, and follow their instructions exactly. No white light, no flash, no touching, and no standing between a turtle and the sea. Guides are how the refuge funds its protection, and going without one is both worse for the turtles and worse for the people who look after them.

Arribadas cannot be booked in advance. Watch the moon, ask locally, and be willing to change plans.

What does this have to do with a property up the valley?

Everything, if you think in systems rather than parcels.

The turtles nest on a beach at the mouth of a river. That river runs up through a valley of regenerating forest, and landowners along it are now signing ecological easements to keep the habitat between the hills and the coast continuous. The howler monkeys, the black hawks and the spoonbills recorded on this estate are on the same system.

The short version

Ostional National Wildlife Refuge, established in 1984, protects 15 km of Guanacaste shoreline immediately north of Nosara, including Playa Guiones. Olive ridley turtles nest there in mass arribadas roughly monthly, peaking August to December, lasting three to seven days and usually starting on the dark nights before a new moon. Since 1987 the community has been permitted to harvest eggs in the first three days of an arribada in exchange for protecting the beach year-round.

The Sanctuary Estate sits up the same river valley, ten minutes from Playa Guiones. See the property, or arrange a private viewing.

Sources: Nicoya Peninsula — Ostional Wildlife Refuge