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Photo from Asoc. de Desarrollo Integral de Ostional – Pag Oficial

QCOSTARICA – The beach of Ostional is the scenery for a rarely-seen biological wonder. In rainy season, the week before new moon, hundreds – and sometimes hundreds of thousand sea turtles take part in the “arribada” (the Spanish word for arrival), which is a vast group of turtles collecting to nest at the same time and place.

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.

Only olive-ridleys and their close relatives, Kemp’s Sea Turtles, the latter an Atlantic species synchronize their nesting in arribadas.

Asoc. de Desarrollo Integral de Ostional - Pag Oficial
Photo from Asoc. de Desarrollo Integral de Ostional – Pag Oficial

Some days or weeks before the mass nesting, the “flotilla”, an increasing number of turtles, congregates close offshore. After some days, prompted by some secret signal, the “arribada” will begin. At first, a few hundred turtles will come out on the beach, followed by a steady stream of animals for the next three to seven days.

In this arribaba, the Ostional Turtle Lodge on its Facebook page says they have recorded the greatest amount of visitors historically to see this phenomenon and remind that Ostional is a small town and that ADIO (Asociacion de Desarrollo Integral de Ostional) and the local guide association have not been able to handle the volume of visitation.

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“Please remember that you are visiting a national wildlife refuge” says the post.

In addition, keep in min that all visitors are required to be accompanied on the beach by a local guide. Flash photography and white lights are not allowed (red lights only). And Please take all of your trash with you, do not leave it on the beach or in town.
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 number of nesting females are in the range of hundreds of thousands as opposed to tens of thousands for the dry season months.
The arribada begins and ends abruptly. More than 150,000 sea turtles congregate offshore in shallow waters. Once the females begin moving towards the shore in droves, they do not stop, continuing through daybreak or disturbance. If the weather is extremely bad, they may delay for a time and retain their eggs until the sky clears. The arribada lasts four to eight days, bringing waves of turtles up the beach at each high tide. At Playa Ostional, 150,000 to 200,000 turtles come to nest in just four days.

With so many turtles nesting in a small area, a lot of eggs are dug up or destroyed by the females who arrive later in the arribada. Costa Rican legislation allows some egg harvesting on Playa Ostional at the beginning of the arribada to use the eggs that would otherwise be crushed.

Although the turtle is protected by law, the olive ridley is still suffering many deaths and the magnificent arribadas are getting smaller. Trawling and fishing during a single arribada can cause devastating losses for this sensitive species. The effects of such damage last a long time.

The olive ridley is a vulnerable species. It is protected by international policies and illegal to hunt.

The following photos are from the  Asoc. de Desarrollo Integral de Ostional – Pag Oficial Facebook page.

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