Green sea turtles (Chelonia mydas) are large marine reptiles inhabiting tropical and subtropical oceans across the globe. Adult green sea turtles are primarily herbivorous, consuming seagrasses and algae, which gives their body fat a distinctive greenish hue. These turtles undertake extensive migrations between their foraging grounds and nesting beaches throughout their lives. Different stages of their life cycle present varying levels of vulnerability to predators, with threats evolving as the turtles grow from eggs to mature adults.
Predators of Eggs and Hatchlings
The earliest life stages of green sea turtles, from eggs to hatchlings, represent their most vulnerable period. Nests, typically laid on sandy beaches, are susceptible to a wide array of terrestrial predators. Mammals such as raccoons, foxes, skunks, opossums, wild dogs, feral pigs, mongooses, and rats often consume the eggs. Crabs, including ghost crabs, along with various birds and even ants, also raid nests.
Once hatchlings emerge, primarily at night, they face numerous predators during their dash to the ocean. Birds like gulls and frigatebirds snatch them from the sand. Ghost crabs lie in wait to prey on the tiny turtles as they scurry towards the water’s edge. Upon entering the ocean, hatchlings become targets for various carnivorous fish. A significant percentage of hatchlings never reach the open sea, and only about 10% survive to adulthood.
Predators of Juvenile Green Sea Turtles
Juvenile green sea turtles encounter new predators in the marine environment. Sharks become a notable threat, with species like the tiger shark and bull shark known to prey on these growing turtles. Tiger sharks’ powerful jaws and serrated teeth are uniquely adapted for crushing sea turtle shells. Silky sharks have also been documented preying on juveniles.
Larger predatory fish, including barracudas and groupers, also target juvenile green sea turtles. For instance, the giant grouper (Promicrops lanceolatus) has been observed consuming juvenile turtles. As green sea turtles grow, their harder shells and increasing size deter many smaller predators. Juvenile turtles typically spend several years in the open ocean before transitioning to shallower coastal habitats.
Predators of Adult Green Sea Turtles
Adult green sea turtles have relatively few natural predators, primarily due to their substantial size and sturdy shells, which can weigh between 400 and 850 pounds. Large shark species are their most prominent natural predators.
Tiger sharks are the main predator of adult green sea turtles. These sharks often hunt near nesting beaches, where female turtles might be more vulnerable due to exhaustion after laying eggs. Other large sharks like white and bull sharks also prey on adults. In some estuarine and coastal regions, crocodiles and alligators can pose a threat. Predation on healthy adult green sea turtles is rare, given their formidable defenses.