The 248-hectare Refugio Nacional Silvestre Vida Ostional begins at Punta India, about two kilometers south of San Juanillo, and extends along 15 kilometers of shoreline to Punta Guiones, eight kilometers south of the village of Nosara. It incorporates the beaches of Playa Ostional, Playa Nosara, and Playa Guiones.

The village of Ostional is midway along Playa Ostional, which has some of the tallest breaking waves in the country. The refuge, one of the world’s most important sea turtle hatcheries, was created to protect one of two vitally important nesting sites in Costa Rica for the lora, or olive ridley turtle (the other is Playa Nancite, in Santa Rosa National Park).

A significant proportion of the world’s Pacific ridley turtle population nests at Ostional, invading the beach en masse for up to one week at a time July–December (peak season is August and September, starting with the last quarter of the full moon), and singly or in small groups at other times during the year. Synchronized mass nestings are known to occur at only nine beaches worldwide (in Mexico, Nicaragua, Honduras, Surinam, Panama, Orissa in India, and Costa Rica).

Time your arrival correctly and out beyond the breakers you may see a vast flotilla of turtles massed shoulder to shoulder, waiting their turn to swarm ashore, dig a hole in the sand, and drop in the seeds for tomorrow’s turtles. The legions pour out of the surf in endless waves. It’s a stupendous sight, this arribada (arrival). Of the world’s eight marine turtle species, only the females of the olive ridley and its Atlantic cousin, Kemp’s ridley, stage arribadas. Ostional is the most important of these.

So tightly packed is the horde that the turtles feverishly clamber over one another in their efforts to find an unoccupied nesting site. As they dig, sweeping their flippers back and forth, the females scatter sand over one another and the air is filled with the slapping of flippers on shells. By the time the arribada is over, more than 150,000 turtles may have stormed this prodigal place and 15 million eggs may lie buried in the sand.

Leatherback turtles also come ashore to nest in smaller numbers October–January, most months starting with the last quarter of the moon.

You can walk the entire length of the beach’s 15-kilometer shoreline. Although turtles can handle the strong currents, humans have a harder time: swimming is not advised. Howler monkeys, coatimundis, and kinkajous frequent the forest inland from the beach. The mangrove swamp at the mouth of the Río Nosara is a nesting site for many of the 190 bird species hereabouts.

Turtle Viewing

You must check in with ADIO (Asociación Desarrollo Integral de Ostional, tel./fax 506/682-0470, adiotort [at] racsa [dot] co [dot] cr, http://ostionalcr.tripod.com), the office is beside the road on the northwest corner of the soccer field, before exploring the beach; a guide is compulsory ($7) any time of year. An entry fee of $8 is payable at the ranger station (tel. 506/682-0400) 200 meters south of the soccer field, behind the Doug Robinson Marine Research Laboratory (tel. 506/207-5966, cachi [at] biologia [dot] vcr [dot] ac [dot] cr). You watch a video before entering the beach as a group.

All vehicles arriving at night are requested to turn off their headlights when approaching the beach. Flashlights and flash photography are also forbidden. Personal contact with turtles is prohibited, as is disturbance of markers placed on the beach.

Getting There

A bus departs Santa Cruz for Ostional at 12:30 p.m. (three hours); it may not run in wet season. You can take a taxi (about $8) or walk to Ostional from Nosara.

The dirt road between Ostional and Nosara requires you to ford the Río Montaña (about 5 km south of Ostional), which can be impassable during wet season; sometimes a tractor will be there to pull you through for a fee. About one kilometer farther south the road divides; that to the left (east) fords the Río Nosara just before entering the village of Nosara and is impassable in all but the most favorable conditions; that to the right crosses the Río Nosara via a bridge and the community of Santa Marta.