The leatherback sea turtle, the largest turtle globally, has a unique appearance. Unlike other sea turtles, it lacks a hard, bony shell, instead possessing a robust, rubbery skin covering its carapace, giving the species its name. These reptiles migrate thousands of miles between feeding and nesting grounds and can dive to impressive depths, reaching nearly 4,000 feet. The survival of this ancient species relies significantly on its specific nesting behaviors.
The Annual Nesting Season
Leatherback turtles lay eggs during a broad nesting season that generally spans from March to October across their global distribution. While this period provides a general timeframe, peak nesting months vary considerably depending on the specific geographic region. For instance, in the United States and Caribbean, the nesting season typically occurs from March through July or August, with peak activity observed in May and June. Conversely, on the Pacific coast of Costa Rica, the nesting season extends from early October through March, with its busiest period in November and December. Environmental cues, such as water temperature and daylight hours, play a role in signaling the onset of nesting behaviors for female leatherbacks.
Nesting Frequency and Intervals
A female leatherback typically lays multiple clutches of eggs within a single nesting season, depositing between four to seven clutches per season on average. The interval between nesting events usually ranges from 8 to 12 days, with a common period being 9 to 10 days. Each clutch typically contains around 85 to 100 fertilized, spherical eggs, about the size of a tennis ball. Additionally, females often deposit 20 to 30 smaller, yolkless eggs, which may help maintain air spaces within the nest. After a nesting season, females return to lay eggs typically every two to four years, allowing them time to recover and replenish their energy reserves.
Ideal Nesting Conditions
Leatherback turtles select tropical and subtropical beaches for nesting. These locations have specific conditions conducive to successful egg development and hatchling emergence. Preferred nesting beaches often feature soft, deep sand above the high tide line, crucial for the female to dig her substantial body pit and egg chamber. Some turtles also favor beaches with a deep-water approach, strong wave action, and a steep slope to the dunes, enabling easier access to nesting sites. These conditions are important for ensuring the structural integrity of the nest, protecting the eggs from inundation or extreme temperatures, and facilitating the hatchlings’ eventual journey to the sea.
The Nighttime Ritual
Nesting occurs almost exclusively at night, providing benefits such as reduced exposure to predators and lower heat stress. A female emerges from the ocean and crawls up the beach, often leaving distinctive tracks. Once she finds a suitable spot, she uses her front flippers to excavate a large depression, known as a body pit. Subsequently, she uses her hind flippers to dig a narrower, deeper egg chamber, which can extend up to 40 inches below the surface, where she deposits her clutch of eggs, including fertile and yolkless eggs. After egg deposition, the female covers the eggs with sand using her hind flippers, then uses her front flippers to camouflage the nesting site before returning to the sea.