Ask any turtle biologist from any country as to the meaning of arribada and chances are their eyes will glaze over, before they begin gushing effusively about the synchronised transition from sea to sand of thousands upon thousands of marine turtles that have a sole purpose in mind.
To those without the benefit of either a grounding in Spanish or an understanding of the basic ecology of marine reptiles, arribada simply means arrival – in this case, the arrival of olive ridley sea turtles (and, to a lesser extent, Kemp’s ridleys) to a few special beaches along the coasts of Costa Rica, Mexico and Nicaragua.
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After reaching their destination, the turtles will leave the sanctuary of the sea for a mass egg-laying event, the sheer size of which must be seen to be believed.
When does the arribada occur?
Primarily occurring in the middle of Costa Rica’s wet season, between August and November, the biggest and best arrivals tend to be dictated by the lunar cycle, with peaks occurring between the start of the third quarter (when the moon is half-illuminated) and the darkness associated with a new moon.
Where are the best places to watch the arribada?
Perhaps the most celebrated location to catch the arribada is at Ostional beach on Costa Rica’s Pacific coast, where peak events can see the arrival of around 300,000 gravid female olive ridleys in just a few days. However, other locations include:
Nancite Beach, Santa Rosa National Park
This is one of the main locations to see the olive ridley arribada in Costa Rica. Here, the biggest events will see about 75,000 females arrive on this beach from 8pm-4am.
Ostional National Wildlife Refuge, Nicoya Peninsula
While the largest known rookery for olive ridleys is in Odisha, India, the best place to see the turtles is on this black volcanic beach, which has 15km of protected shoreline.
Tortuguero National Park
Located on the northern Caribbean coast of Costa Rica, Tortuguero translates as ‘region of the turtles’. Between August and September, its beach hosts the largest nesting site for green turtles in the western hemisphere.
Corcovado National Park, Osa Peninsula
The idyllic beaches here see the arrival of smaller numbers of olive ridley, hawksbill and green turtles from July to November, depending on the species.
Grande Beach, Las Baulas National Marine Park
This beach near Tamarindo is home to the world’s second-largest nesting site of the leatherback turtle. Tours are available to watch the spectacle from October to mid-February.
What types of turtle take part in an arribada?
While the precise origins of the word ‘ridley’ are uncertain, the ‘olive’ part undoubtedly refers to the colour of the turtle’s heart-shaped shell. The ridley species are the smallest of the world’s seven species of sea turtle. Of the two, the olive ridley is the most widespread, as it can be found across the tropical regions of all three great oceans.
Considered a mostly pelagic (or open ocean) species, having been observed at more than 3,800km from land, olive ridleys do also inhabit coastal areas. Their varied diet includes crustaceans, molluscs, jellyfish and algae. They can easily live to 50 years old, reaching sexual maturity at the age of 10 to 15. And while other turtle species have been documented to ‘nest’ in groups, only the ridleys appear to do mass egg-laying.
What happens in the arribada?
Returning to the site where they too hatched, the turtles will wait in the shallows for nightfall before leaving the water in waves (both physically and metaphorically). They then move high up the beach, where each turtle digs a shallow hole before laying around 100 rubbery eggs that look like ping-pong balls.
Once the clutch is complete, the female uses her body to cover the eggs with sand and then returns to the water. Witnesses of the spectacle have said that the turtles appear to be in a trance-like state for their entire time away from the sea.
At Ostional, with so many turtles coming ashore on a relatively small section of beach, a large proportion of the earliest clutches are destroyed by the later females either trampling the eggs or unearthing them while making their own deposits. And during the incubation, even more eggs are lost to dogs, racoons, crabs and even ants.
But for those clutches left undisturbed, another wave of activity occurs around 45 days later as the hatchlings start sticking their heads out of the sand. It’s a brutal world and many of these baby turtles will simply serve as cannon fodder.
But in their favour is the beauty of the synchronous laying strategy that gradually becomes apparent – any predators lying in wait quickly become overwhelmed by the sudden emergence of a veritable army of hatchlings.
The tiny turtles’ perilous haul across the sand is akin to a marathon across the world’s most dangerous obstacle course but many make it to the water. In fact, the journey is vital for expanding their lungs and honing their homing instincts – a skill those who reach adulthood will need to return.
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What's the largest recorded arribada?
November 1995 saw the largest ever recorded arribada in Ostional, with up to 500,000 females estimated to have come ashore in a single event.
Can you touch the eggs?
Uniquely in Ostional, locals can take and sell turtle eggs during the first 36 hours of an arribada. It’s controversial but long-term studies suggest the population can sustain a controlled harvesting. In return, villagers clean the beach and patrol for poachers.
What is the turtle code of conduct?
A visit to a nesting site contributes to the conservation of turtles, but it is important to choose a reputable tour operator and guide. They will ensure small group sizes and keep you informed about the rules and regulations – such as no flash photography, wearing dark clothes and keeping at least 1.5m from the turtles.
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