The extensive Ostional Beach and Nancite Beach in Santa Rosa Nacional Park represent the two most important nesting areas for the olive ridley sea turtle (Lepidochelys olivacea) in the world. The usual laying zone, some 900 m long, is situated between the estuary of the Ostional River, which runs parallel to the beach, and a rocky point that extends into the sea. From July to November, turtles gather in great numbers, usually at night and during the waning quarter of the moon. The leatherback turtle (Dermochelys coriacea) also occasionally lay there.
In this refuge a programme of monitored egg collection of the first clutches of olive ridley turtles is underway. It is authorized and supervised by the ministry of the Environment and Energy.
The refuges's scarce vegetation is made up of mixed woodland of deciduous species, including the frangipani (Plumeria rubra). One can also see howler monkeys (Alouatta palliata) there and white-faced capuchin monkeys (Cebus capucinus). Near to the beach among cacti and other succulent plants, ctenosaurs (Ctenosaura similis) are very common. To the southeast of the mouth of the River Nosara, there is quite a large mangrove swamp where over a hundred bird species have been identified.
The area near Punta India at the northwest end is rocky and presents a large number of tidal pools that form along extensive abrasion platforms that have gradually emerged. Small fish and numerous marine invertebrates can be seen in them.
Ostional is located on the Nicoya Peninsula on the Pacific coast. It is 50 km from Nicoya via Curime-Nosara. We recommend using a four-wheel drive vehicle especially during the rainy season. In the area surrounding the refuge there are hotels, cabins and grocery stores. For information on this refuge, call (506) 680-1820.