Ancient marine reptiles found in warm and temperate waters globally, sea turtles play a role in marine ecosystems. Their journey from egg to adulthood is fraught with dangers. They face natural predators at various life stages, yet human activities pose some of the most pervasive threats to their continued existence.
Predators Targeting Early Life Stages
Sea turtle eggs and hatchlings face overwhelming predation pressure. On nesting beaches, various animals seek out and consume buried eggs. Common terrestrial predators include raccoons, foxes, wild dogs, and ghost crabs, which can dig up nests. Fire ants and monitor lizards also pose a threat depending on geographic location.
Once hatchlings emerge, their journey across the sand to the ocean exposes them to numerous predators. Birds such as gulls and frigatebirds often prey on hatchlings during this dash. Crabs and coyotes are also dangers on the beach. Even in the water, hatchlings are consumed by various fish and sharks. Estimates suggest that fewer than one in 1,000 to one in 10,000 sea turtle eggs reach adulthood due to intense early predation.
Predators of Maturing and Adult Sea Turtles
As sea turtles grow, their natural predators become fewer. Primary natural predators of maturing and adult sea turtles are large marine animals. Sharks, particularly tiger sharks, frequently prey on larger juvenile and adult sea turtles. Tiger sharks possess strong jaws and serrated teeth capable of cutting through a turtle’s thick shell.
Other large sharks, such as great white sharks and bull sharks, have also been recorded preying on sea turtles, though less commonly. Orcas, or killer whales, may occasionally target adult sea turtles, including leatherbacks. While adult sea turtles are generally more resilient, sick or injured individuals are more susceptible to these attacks. In coastal areas, saltwater crocodiles and jaguars have been observed preying on nesting female turtles on land.
Threats from Human Activities
Human activities are a significant source of harm to sea turtle populations. Bycatch, the accidental capture of sea turtles in fishing gear like trawls, longlines, and gillnets, is a major issue. When entangled, turtles can suffer injuries, drown, or die from exhaustion, with an estimated 40% of bycaught animals not surviving.
Habitat loss and degradation also impact sea turtles. Coastal development can destroy nesting beaches, while artificial lighting disorients hatchlings, causing them to move away from the ocean towards land, where they face dehydration, predation, or vehicle strikes. Degradation of foraging grounds, like seagrass beds and coral reefs, further reduces their food sources and shelter.
Pollution is another pervasive threat. Sea turtles often mistake plastic debris for food, leading to ingestion that can cause internal injuries, blockages, or false feelings of fullness, resulting in starvation. Entanglement in discarded fishing gear, often called “ghost nets,” can also lead to injury, impaired movement, and drowning. Chemical pollution from industrial and agricultural runoff can accumulate in their tissues, affecting organ function, reproduction, and immune systems, potentially leading to disease.
Vessel strikes, collisions with boats, are a common cause of injury and mortality, especially in high-traffic areas. Sea turtles are vulnerable to these strikes when they surface to breathe, bask, or forage in shallow waters. Climate change impacts sea turtles through rising sea levels and increased storm frequency, eroding and flooding nesting beaches. Warmer sand temperatures also skew hatchling sex ratios, producing more females and potentially affecting future reproductive success.