Sea turtles inhabit nearly all the world’s oceans, excluding polar regions. They play an important role in marine ecosystems, contributing to the health of seagrass beds, coral reefs, and food webs. Despite their widespread presence, sea turtles face a complex array of challenges that threaten their survival across their life stages.
Natural Predators Across Life Stages
Sea turtles encounter various natural predators throughout their development. Vulnerability decreases as they grow larger. The earliest and most susceptible stage is the egg, laid in nests on sandy beaches. Predators such as raccoons, foxes, wild pigs, dingoes, monitor lizards, and various bird species like crows and gulls often unearth and consume sea turtle eggs before they hatch. Crabs, including ghost crabs, also pose a threat to nests on land.
Hatchlings face a high risk of predation as they emerge from their nests and make their perilous journey to the ocean. Mammals like raccoons and foxes, birds, dogs, and crabs prey on them as they crawl across the sand. Once in the water, large bony fish, sharks, and seabirds pose a threat. Only about 1 in 1,000 to 1 in 100,000 hatchlings survive to adulthood due to this intense predation.
As sea turtles mature into juveniles and sub-adults, their increasing size and developing shells offer more protection. They remain prey for larger marine predators such as tiger sharks, bull sharks, barracudas, and groupers. Tiger sharks frequently prey on larger juvenile and adult sea turtles.
Adult sea turtles, due to their substantial size and hardened carapaces, have few natural predators. Large sharks, especially tiger sharks, are the primary marine threat. Killer whales also prey on leatherback sea turtles. On land, nesting adult females can be attacked by jaguars, American crocodiles, saltwater crocodiles, and wild boars.
Significant Threats to Sea Turtle Survival
Beyond natural predation, sea turtles face substantial threats from human activities. Bycatch in fisheries is a widespread danger, where turtles are unintentionally caught in fishing gear. Trawls, longlines, and gillnets lead to injuries, drowning, and high mortality rates for entangled turtles. A 2010 study estimated that 1.5 million sea turtles were caught in fisheries globally over an 18-year period.
Coastal development and habitat degradation also challenge sea turtle populations. Expansion of human infrastructure along coastlines destroys nesting beaches. This development can block turtles’ access to nesting areas and disrupt their reproductive cycles. Light pollution from coastal areas disorients hatchlings, drawing them away from the ocean and increasing their vulnerability to predators. The destruction of foraging habitats, such as seagrass beds and coral reefs, impacts their ability to find food.
Pollution represents another threat, with plastic debris being harmful. Sea turtles often mistake plastic bags for jellyfish, leading to ingestion that can cause internal injuries, blockages, or starvation. Entanglement in discarded fishing gear and other marine debris can maim, amputate limbs, restrict movement, or cause drowning. Chemical pollution and oil spills degrade marine habitats and can poison sea turtles, impacting their health and reproductive success.
Climate change alters environmental conditions for sea turtles. Rising sea levels threaten to inundate nesting beaches, reducing available areas for reproduction. The sex of sea turtle hatchlings is determined by sand temperature during incubation, with warmer temperatures producing more females. Increasing global temperatures are leading to highly female-skewed sex ratios in some populations, jeopardizing future reproductive success and genetic diversity due to a lack of males.
Direct harvesting of sea turtles for their meat, eggs, and shells continues in some regions, though it is less common and often illegal today. Hawksbill turtles were heavily hunted for their ornate shells, used for jewelry and curios. While conservation efforts have reduced this practice, illegal trade persists.