Many female olive ridley sea turtles (Lepidochelys olivacea) are swimming from the open ocean towards the beach of Ostional, Costa Rica, Pacific Ocean to gather for an mass nesting event. The arrival of one olive ridley sea turtle (Lepidochelys olivacea) at the beach, can be the beginning of an arribada (mass nesting event) of the sea turtles. Thousands and thousands of the 50 kilogram reptiles come ashore over a period of up to a week, only interrupted by the hottest midday sun, to bury their eggs in the warm sand. It takes nearly two months for a sea turtle egg to develop in a perfect little marine reptile. The hatchlings on their way to the sea orient themselves by the brightness of the horizont above the ocean and they are always at risk of being eaten by birds, crabs or later by fish. Being in a group at least on the beach enhances the chances of the single animals to survive. As soon as the hatchling enters the water the young olive sea turtle struggles against the swell to swim away from the coast. The so-called swimming frenzy lasts for approximately 48 hours to keep the hatchlings from being washed ashore. The turtles do not feed within the first days as they live on the reserves they acquired from the yolk in their eggs. The swimming hatchlings often fall prey to e.g. fregate birds or larger fish.
The community of Ostional, Pacific coast of Costa Rica, runs a project of sustainable use of the olive ridley sea turtles (Lepidochelys olivacea). The eggs, a popular snack in Costa Rica, are harvested during the first days of a large arribada, and bagged for legal and controlled sale throughout the country. A large arribada event may include hundreds of thousands of female olive ridleys. As many nests of the early nesters are destroyed by the following turtles it seems possible to take the early eggs without influencing the future population of this species, listed as vulnerable in the IUCN red list. However, the project at Ostional is a very complex activity influencing in many ways the likewise complex and not fully studied ecology of a sea turtle. The olive ridley may be less secure as it superficially appears to be when witnessing the high numbers of nesting females at Ostional. Measured by the numbers of nests laid this beach is the most important nesting area for this species in the world.