The beach of Ostional is the scenery for a rarely-seen biological wonder. Around the third quarter of the moon, hundreds, and sometimes hundreds of thousands of sea turtles come to one specific mile of beach at Ostional to dig their eggs into the black, volcanic sand. The beach of Ostional is the scenery for a rarely-seen biological wonder. Around the third quarter of the moon, hundreds, and sometimes hundreds of thousands of sea turtles come to one

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 mass emergences or "arribadas", the Spanish word for arrivals.

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.

Turtles nest at Ostional year round, but the 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 largest "arribada" thus far recorded in Ostional, took place in November 1995 when a calculated 500 000 females came ashore.

The turtles generally ride in on the high tide at night but during an arribada they start arriving around 4 p.m. and keep coming until 7 a.m. the next morning.

Used to a life in the ocean, the turtles awkwardly drag their heavy bodies over the beach until they get over the high tide line. Flicking clouds of sand, they dig a nest with their flippers to deposit about 105 white, ping pong-shaped eggs.

Over the course of a five-day arribada nesting turtles will leave up to 10 million eggs on the beach of Ostional

Amazingly, Ostional is the only beach in the world where egg poaching is legal. Scientists found out that most of the eggs deposed in the first nights of an arribada are destroyed by subsequent turtles who dig their nests. Therefore, since 1987, the government of Costa Rica allows on an annual, temporary suspension of the international ban on turtle-egg taking that the community of Ostional may harvest the doomed eggs on the first two dawns of an arribada. In return, the community must protect the turtles, clean debris from the beaches and patrol day and night for poachers.

The baby turtles hatch within 45-54 days depending on incubation temperatures, which will also determine if they will become male or female. They face varying degrees of success in each of the clutches that are laid in large groups to increase their success of surviving.

In general the baby turtles hatch at night, but it may also happen that you are sitting in the afternoon on the beach and suddenly, next to you the sand becomes live and small heads pop up.

As soon as the hatchlings have struggled out of the sand, the race to the ocean begins. With eyes barely opened, the mini turtles smell the breeze and instantly know the right direction.

Women and children from the community of Ostional accompany the hatchlings as they clamber toward the sea, protecting them from dogs and vultures.

If you also want to help the small turtles you shouldn't carry them all the way to the beach as they need the run to develop their lungs. You can carry them a piece of way over the hottest stretch of sand and let them run the rest just trying to provide them some shade and keep the vultures away.

Having reached the ocean, the mini turtles still aren't safe - the next cast of predators awaits them under water.

Most hatchlings don't reach maturity, but those who make it will remember the smell of their beach. After 10 - 15 years they will return to their place of birth and again lay their eggs into the black sand of Ostional.

Duration: 3 to 4 hours

What to wear: Hiking shoes, pants and T-shirt

What to Bring: Camera (during the night no pictures are allow it) insect repellent.  A small flashlight with red lens, this is soft on their eyes and will not distract the turtles as much as white light.

Included: Air-conditioned round trip transportation, entrance fee to the park and guide.

Cost: $30 per person

Regulations and policies: All tours must be reserved with 24 hours in advance for the proper schedule of activities. Cancellation of a tour must be within 24 hours. Reef Travel does not have any responsibility or liability for any accident that could occur on such activity.