Sea Turtle Nesting in Guanacaste: Where to Go and How to Watch Responsibly

Guanacaste’s one dependable turtle spectacle is the olive ridley arribada at Ostional, where 15,000 to 200,000 females come ashore over a few nights, once or twice a month, all year. Near Tamarindo, guided night tours walk beaches outside the national park for olive ridleys and East Pacific green turtles, roughly mid-November to mid-April. Leatherbacks are the exception: Las Baulas National Marine Park exists for them, but SINAC’s own page says there is no turtle observation there, and the park’s leatherback tour has been suspended since 2018.

The Ostional National Wildlife Refuge covers four beaches — Ostional, Nosara, Pelada and Guiones — and protects the world’s most important olive ridley nesting site, second only to Playa Escobilla in Mexico for mass nesting. The arribadas crowd into roughly 800 metres of a seven-kilometre beach.

They happen all year, once or twice a month, and bring 15,000 to 200,000 females ashore. The rainy-season events from July to November are the big ones: Nosara’s Wildlife Conservation Association says September and October arribadas can bring up to half a million turtles and run three to four days, against tens of thousands over two or three nights from December to June. In early September 2026 the local guides’ association announced an arribada starting Friday 5 September, expected to last five to six nights with the first three busiest.

Nobody knows in advance when the next one starts. For a realistic chance, base yourself in Nosara for several nights in the rainy season and follow the guide associations.

Ostional is one of very few places on earth with a legal, regulated take of sea turtle eggs, and visitors are often startled by it. The reasoning is density: so many females nest in the same strip of sand that later arrivals dig up nests laid days earlier, and broken eggs lower hatching success for everyone. Members of ADIO may collect a share of the eggs in the first days of an arribada, under permits, environmental controls and traceability rules. In return the community protects the beach and patrols against poaching.

Outside that system, taking eggs is a crime: on 7 September 2026 two people who did not belong to ADIO were detained with 125 olive ridley eggs from about two nests. Don’t buy eggs, and don’t pick one up on the sand.

Las Baulas National Marine Park was created to protect the leatherbacks nesting at Playa Grande, Playa Ventanas and Playa Langosta, and three species still visit: leatherback, olive ridley and the black turtle. It opens daily 6am to 6pm, and in the October–February nesting season you must be off the beach by 5pm. Its two entrances take a combined 120 people, 60 per gate.

Now the part most articles skip. SINAC’s page for the park currently states, in plain Spanish, that there is no turtle observation, and that estuary visits are made with local guides, no booking needed. The leatherback nesting season runs 1 October to 15 March, but only eight nesting leatherbacks were identified in the park in 2021–22, and fewer than ten now come in a whole season — residents remember 30 to 40 a night in the late 1980s. The Eastern Pacific population has fallen by more than 98% since 1990. The park suspended guided viewing shortly before the pandemic, and the published tour procedure has carried a “suspended since 2018” notice ever since.

So if a website offers you a leatherback tour at Playa Grande, treat it as out of date. What you can do here is walk and surf the beach by day, and take a guided trip through the mangroves: the Tamarindo estuary boat safari runs two hours inside the park, from $52 per person. Dogs, single-use plastics, fires, beach vehicles and horse rides are banned, as is touching or feeding any animal.

Because the park tour stopped, guiding moved to beaches outside it. RipJack Inn at Playa Grande says tours now visit nearby protected beaches such as Playa Minas, with an official season of 15 October to 15 February — which doesn’t match the operators’ own windows, a reminder that these are ranges, not timetables. Two night tours in our catalog leave from Tamarindo:

Expect a lot of waiting and a real chance of seeing nothing. Prices are “from” prices per person in our catalog in September 2026 and change. For how a turtle night fits into a Tamarindo week, see our day trips from Tamarindo.

Hatchlings find the sea by crawling toward the brightest horizon. On a dark beach that is the water; near lights it is the road, where they are eaten, run over or die of exhaustion. Adult females misorient toward lights or crawl in circles, and many give up. SINAC puts it directly on the Ostional page: light can frighten a female into abandoning the nest she has started, leaving the eggs uncovered for predators.

Red light is less disruptive, not harmless. Conservation groups that work nesting beaches are blunt: red spectrums still have real potential to change turtle behaviour, and species react differently. The light belongs to the guide, not to you.

The crawl from nest to sea is not a formality the turtle can skip. NOAA Fisheries’ guidance is not to swim with, ride, approach, touch or interact with wild sea turtles, and to watch from far enough away that a turtle’s whole body fits between your fingers at arm’s length. Only permitted researchers handle turtles, nests or hatchlings. If an “experience” offers to put a hatchling in your hand, leave.

Two smaller habits matter more than they sound: fill in the holes you dig and flatten sandcastles, because hatchlings fall in and females get stuck, and clear chairs, umbrellas and canopies off the beach at night.

If your dates miss every turtle season, Guanacaste still has good wildlife days: a guided hiking and birdwatching walk in Nosara (1.5 hours, binoculars and telescope provided, from $65) or a safari float on the Nosara River (2 hours, from $70). Our dry vs. green season guide helps you pick dates.