One of the year’s biggest olive ridley sea turtle arribadas kicked off on September 13 at Ostional Beach in Costa Rica’s Guanacaste province. Thousands of females have come ashore to nest, covering the sand in a dense wave of activity. As of September 20, the event moves into its closing days, with fewer turtles arriving each night.
The Ministry of Environment and Energy (MINAE), via the Tempisque Conservation Area, reports this as a major nesting push. Olive ridley turtles (Lepidochelys olivacea) show this group behavior only on select coasts, and Ostional ranks as the world’s second-largest site after Playa Escobilla in Mexico. These arribadas happen year-round, once or twice monthly, drawing 15,000 to 200,000 females over a few days along seven kilometers of beach.
Arribadas, or mass nesting events, begin when females gather offshore—sometimes for days or weeks—before surging onto the beach together to dig nests and lay eggs. This synchronized rush helps overwhelm predators but leads to overcrowded nests, where later arrivals often dig up earlier ones. Ostional stands out as one of about 15 known arribada sites worldwide, with five major locations seeing over 100,000 nests annually and others hosting smaller events.
In this latest push, tens of thousands have nested, making it one of the most significant of 2025. While hatch rates stay low due to the density, the sheer egg volume leads to thousands of baby turtles emerging later. Costa Rica manages this through a community-led system at the Ostional National Wildlife Refuge, working with the Ostional Integral Development Association and experts from the University of Costa Rica.
The refuge spans 468 land hectares and 8,000 marine hectares, guarding beaches like Ostional, Nosara, Peladas, and Guiones. Ostional sits in Santa Cruz canton, while the others fall under Nicoya canton. This setup lets locals harvest eggs sustainably in the first days of an arribada, balancing protection with economic needs.
Visitors from around the world flock here annually to see the turtles in action. Peak season wraps up soon, but arribadas continue into 2026, with strong showings expected in October and November. To catch this one before it ends, book a guided tour—night visits offer the best views, as turtles often arrive after dark.
MINAE advises reaching out to certified guides for safe access. Contact the Ostional Local Guides Association at +506 2682-0428 or 6252-7412, the Ostional Integral Development Association at +506 2682-1229 or 6108-1681, or email info@sinac.go.cr for details. Rules require sticking to marked paths to avoid disturbing nests.
