Sea turtles, ancient reptiles, have traversed the world’s oceans for millions of years. These migratory creatures journey across vast distances. Their lives, largely hidden beneath the waves, continue to fascinate. From tiny hatchlings to adulthood, their existence remains a subject of ongoing study, revealing the complexities of life in the marine environment.
The Mating Question Answered
Sea turtles do not form long-term pair bonds or mate for life. Instead, they engage in a reproductive strategy where both males and females typically have multiple partners during a single breeding season. Such a system is common in the marine environment, where individuals are often widely dispersed.
Mating activities occur seasonally, often in coastal waters near the nesting grounds. Females can store sperm for extended periods after mating, allowing them to fertilize subsequent clutches of eggs without needing to re-mate for each nesting event. This adaptation is significant for species that undertake long migrations and nest multiple times within a season.
Understanding Sea Turtle Reproduction
The reproductive cycle begins with males and females congregating in specific breeding grounds, typically offshore near nesting beaches. During courtship, male sea turtles approach a female and initiate contact by biting her neck and flippers. If receptive, the male mounts her back, using claws on his front flippers to maintain a grip on her shell.
Copulation takes place in the water and can last for several hours. After mating, females have the capacity to store sperm within their reproductive tracts. This allows them to lay multiple clutches of eggs over a period of weeks, potentially fertilized by sperm from one or several males from a single mating encounter. Once the mating season concludes, male sea turtles typically remain at sea, while females embark on their journey to nesting beaches.
Nesting and Hatching
After successful mating, female sea turtles journey to their chosen nesting beaches, often returning to the area where they hatched decades earlier. Upon reaching the sandy shore, the female selects a site above the high tide line. She uses her front flippers to excavate a body pit, then her hind flippers to dig a deeper, flask-shaped egg chamber.
Within this chamber, she deposits her clutch of eggs, varying from about 50 to 200 depending on the species. A female may lay multiple clutches, typically 2 to 8, within a single nesting season, with intervals of 10 to 15 days between events. Once laid, she covers the nest with sand, camouflaging its location before returning to the ocean.
The eggs incubate in the sand for 45 to 70 days, though this can extend up to 80 days depending on species, clutch size, and environmental temperature. Sand temperature during incubation determines the sex of hatchlings, a phenomenon known as temperature-dependent sex determination (TSD). Warmer sand temperatures typically produce more female hatchlings, while cooler temperatures result in more males. A temperature around 29°C (84.2°F) tends to yield an equal ratio of males and females.
When ready, hatchlings collectively emerge from the nest, often at night, in what is described as a “turtle boil.” They instinctively orient themselves towards the brightest horizon, typically the open ocean. This initial journey to the sea is a race, and once they reach the water, they enter a “swim frenzy” to move quickly away from nearshore predators. Despite the large number of eggs laid, only a small fraction, about one in a thousand, survive to adulthood.