Sea turtles undertake massive reproductive efforts, with females returning to nesting beaches every few years to lay hundreds of eggs. This immense investment exists because a dramatic difference separates the number of eggs laid from the few individuals that ultimately survive to adulthood.
The Harsh Survival Rate
The percentage of baby sea turtles that survive their journey to reproductive maturity is extremely low. Estimates suggest that only one in 1,000 to one in 10,000 hatchlings will successfully reach the age where they can reproduce. This low percentage reflects the species’ natural life history strategy, which relies on mass production rather than parental care.
Survival means reaching sexual maturity, a milestone that can take anywhere from 10 to 30 years, depending on the species. The initial moments of a sea turtle’s life are the most dangerous, creating a steep decline in population almost immediately.
Threats During the Hatchling Phase
The first few hours of life present a gauntlet of dangers for hatchlings as they emerge from their nests and race toward the ocean. Natural predators such as ghost crabs, raccoons, and seabirds congregate on nesting beaches, ready to ambush the vulnerable newborns. These terrestrial threats can significantly reduce the number of turtles that make it past the high-tide line.
Artificial light sources from coastal development are a primary human-caused threat. Hatchlings instinctively navigate toward the brightest horizon, but building lights or streetlamps can disorient them, leading them inland. There, they perish from dehydration, exhaustion, or being struck by vehicles. Physical obstacles left on the beach, like tire ruts, furniture, or deep holes, can also trap or delay the tiny turtles, increasing their exposure to predators and heat.
Dangers in the Pelagic Zone
Once the hatchlings reach the surf, they begin an intense “swimming frenzy” that lasts for a day or two, propelling them away from nearshore waters. They then enter the open ocean, beginning the “lost years,” which may last for a decade or more. During this time, they drift with ocean currents.
The hatchlings often find refuge and food within floating patches of seaweed, such as sargassum, which aggregate along ocean fronts. This floating habitat provides cover from marine predators like large fish, yet it also concentrates marine debris. Young turtles frequently ingest plastic pieces, mistaking them for food, which can lead to blockages and starvation.
Hatchlings and juvenile turtles are also vulnerable to being caught as bycatch in commercial fishing gear, particularly longlines and trawls. Strong storms and changing ocean currents can also displace them from their warm-water nurseries.
The Rationale of High Mortality
The low survival rate is part of a natural biological strategy known as R-selection. This strategy is characterized by the production of numerous, inexpensive offspring with minimal parental investment. A female sea turtle can lay hundreds of eggs across multiple nesting events in a single season. This high output is an evolutionary answer to high juvenile mortality.
By producing a large number of offspring, sea turtles ensure that even a tiny percentage of survivors is enough to replace the parents and maintain the population size. The parents do not expend energy on caring for the young, instead focusing their resources on maximizing the number of eggs laid. This ancient strategy works efficiently, provided the natural causes of mortality are not intensified by human activity.