Ostional Wildlife Reserve
The beach of Ostional is the scenery for a rarely-seen biological wonder. The week before new moon hundreds, and sometimes hundreds of thousand sea turtles come to one specific mile of beach at Ostional to dig their eggs into the black, volcanic sand.
The black-sand beach of Ostional
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.
(See also: Sea turtles in the Wildlife Guide)
Sea turtle swimming in the ocean
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 arriving in Ostional
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 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 soon after sunset and keep coming until 6 am the next morning.
Turtle laying eggs into the sand
Used to a life in the ocean, the turtles painfully drag their heavy bodies over the beach until they get over the high tide line. There, flicking clouds of sand, they dig a nest with their flippers to deposit around 80 - 100 soft-shelled, white eggs, the size of a ping pong ball.
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 harvesting turtel eggs 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 the community of Ostional to harvest the doomed eggs on the first three days of an arribada. In return, the villagers protect the turtles, clean debris from the beaches and patrol day and night for poachers.
Small turtles hatch after around 50 days
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 are eager 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, while keeping the vultures away.
Having reached the ocean, the mini turtles still aren't safe - the next cast of predators awaits them under water.
Olive ridley sea turtle in Ostional
Most hatchlings don't reach the age of maturity which takes 10 - 15 years, but those who make it will remember their home beach.
Adventurous turtles may paddle across the Pacific ocean as far as India but their impressive natural navigation system steers them back
to their place of birth in Ostional where they will lay their eggs again into the black sanded beach, like their mother once did.
The Ostional Wildlife Reserve extends 15 km along the shoreline, including the beaches of Ostional, Nosara and Guiones. It is only a narrow, 200 m wide strand of beach, but extends inland along the estuaries of the rivers and mangrove swamps, protecting also large colonies of birds. Offshore the reserve incorporates another 3 miles stretch of maritime zone.
Vultures in Ostional preying on turtle eggs
During nesting season (Aug - Nov) solitary turtles arrive almost every night at Ostional and sometimes the rare and endangered giant leatherback turtles
and green sea turtles come to nest as well.
On a daytime walk on the beach you see lots of white shreds from broken turtle eggs and crowds of black vultures sitting in wait for hatching turtles or picking and scratching impatiently with their beaks in the sand to get to the tasty eggs.
At night, when there is an arribada, you must check in with the ranger booth at the southern end of Ostional where you pay the entrance fee of $ 10. No flashlights or flash photography is permitted.
Arribadas usually occur during the darkest nights: a few days before the new moon. The majority of turtles arrives between 8 pm and 4 am.
For taking pictures it's best to go to the beach at dawn, when the last of the turtles digg their nests. Turtle fans can stay overnight in the village of
Ostional which has a few nice and inexpensive cabina places.
How to get to Ostional:
Ostional is a short drive from Nosara. From the Beaches of Nosara, drive 2 kms until the turnoff to Santa Marta to the left. From here it is 7 kms to Ostional. A bridge leads over the Nosara river but there is only a hanging bridge for people over the Rio Montaña. Cars have to ford the river which can be impossible in rainy season. Tour operators will have a second vehicle on the other side of the river. Most hotels in Nosara arrange tours to Ostional when there is an arribada.
Coming from the north, a road goes to Ostional south-west from Santa Cruz or south from Junquillal via Marbella and San Juanillo. For most of the year this road is in rather good condition, but Sept/Oct a 4x4 is advisable.
From Santa Cruz a bus runs daily at noon time to Ostional (3 hours) and returns to Santa Cruz at 5 a.m.
As the arribadas occur during the peak of rainy season it is sometimes not possible to get to Ostional or to leave from there.