The period between October and March at Playa Grande, Costa Rica, is dominated by one of the world’s most significant annual wildlife migrations. This stretch of sand, located on the Pacific coast, is recognized as a globally significant site for the conservation of the Leatherback Sea Turtle, the largest marine reptile species. The seasonal cycle begins with the arrival of adults and concludes with the emergence of their offspring. All activity occurs within the protected boundaries of the Las Baulas National Marine Park, drawing international attention to the region’s seasonal rhythm.
The Peak Season for Leatherback Nesting
The October-to-March window marks the arrival of adult female Leatherback Sea Turtles (Dermochelys coriacea) to the shores of Playa Grande for their reproductive cycle. These animals, which can weigh up to 700 kilograms (over 1,500 pounds), are protected upon arrival within the park’s boundaries. The nesting season begins in October and typically runs through the end of February, peaking between November and February.
Female leatherbacks emerge from the Pacific Ocean under the cover of darkness, usually coinciding with high tide to minimize the crawl distance to a suitable nesting spot. After digging a deep, flask-shaped nest chamber, the turtle lays a clutch of approximately 50 to 200 eggs. A single female may return to the beach multiple times during the season, nesting every ten days.
Playa Grande represents one of the few remaining nesting sites for the Eastern Pacific population of this endangered species. The concentration of nesting activity underscores the beach’s importance to the Leatherback’s survival. The act of egg-laying is an energy-intensive process that can take several hours. Afterward, the female covers the nest and returns to the ocean.
The Subsequent Hatching Phenomenon
Following the nesting period, the focus shifts to the next generation incubating beneath the sand. The eggs remain in the nest chamber for an incubation period ranging from 45 to 70 days. This duration is influenced by sand temperature, which also determines the sex of the hatchlings.
The emergence of the young turtles begins in late December or early January and continues through March, sometimes extending into May. Guided by instinct, these hatchlings erupt from the sand and immediately begin their journey toward the ocean. This spectacle occurs just before sunrise or after sunset, taking advantage of cooler temperatures.
The hatchlings must use their limited energy to cross the beach, heading toward the brightest horizon, ideally the reflection of the moon or stars on the water. This scramble is a moment of high drama, as the young turtles face natural predators like birds and crabs. Only a small fraction of the hatchlings will survive to adulthood and return years later to reproduce on this beach.
Seasonal Climate and Visitor Logistics
The October to March period brings a change in weather to the Guanacaste region, moving from the end of the rainy season into the height of the dry season. October and November mark the transition, sometimes experiencing lingering rain showers. By December, the weather becomes noticeably drier and sunnier, and by March, the area is typically hot and arid, characterized by high temperatures that can reach 33°C (92°F).
Visiting Playa Grande at night to witness nesting or hatching is controlled as part of conservation efforts within Las Baulas National Marine Park. Independent access to the beach is prohibited between 6:00 PM and 6:00 AM during the nesting season to protect the turtles from disturbance. Observing the turtles is only possible through guided tours led by certified local guides or park rangers.
The park enforces strict viewing protocols to minimize human impact on the nesting process. Regulations mandate that visitors must not use flash photography or bright white lights, relying instead on red-light flashlights for navigation. The number of visitors allowed on the beach each night is restricted, with limited group sizes. Reservations well in advance are a necessity for anyone hoping to witness this unique biological event.