Green sea turtles, named for the greenish tint of their body fat rather than their shell, are large marine reptiles found in tropical and subtropical waters worldwide. They are unique among sea turtle species due to their distinct dietary habits, which undergo a significant transformation throughout their lives. Understanding their diet provides insight into their ecological role and habitat requirements.
Dietary Shift Through Life Stages
The diet of a green sea turtle changes considerably from hatching to adulthood. As hatchlings, they begin with a predominantly carnivorous diet, consuming small organisms found in the open ocean. This early diet includes worms, small crustaceans, aquatic insects, fish eggs, hydrozoans, and jellyfish, often found within pelagic drift communities like Sargassum clusters.
As green sea turtles mature into juveniles, their feeding habits gradually shift to become more omnivorous, incorporating plant matter alongside animal prey. They may still consume invertebrates, sponges, crabs, and discarded fish, but they also begin to graze on seagrass and algae. This transition prepares them for their adult diet, which is almost exclusively plant-based.
Primary Food Sources of Adults
Adult green sea turtles are primarily herbivores, making them the only sea turtle species with a strictly plant-based diet at this life stage. Their main food sources are seagrasses and various types of marine algae.
Common seagrasses consumed by adult green sea turtles include turtle grass (Thalassia testudinum), known for its broad, flat leaves, as well as shoal grass (Halodule wrightii) and manatee grass (Syringodium filiforme). They also graze on a wide range of algae, such as green algae, red algae, sea lettuce (Ulva lactuca), and red moss. Their jaw structure is specifically adapted for this diet, featuring finely serrated edges that function like shears to tear tough vegetation and scrape algae from surfaces.
Foraging Behavior and Habitat
Green sea turtles exhibit specific foraging behaviors and utilize distinct habitats to find their food. Mature turtles spend most of their time in shallow, coastal waters, including inshore bays, lagoons, and shoals that contain abundant seagrass beds. They are often observed grazing on algae attached to coral rocks and consuming strands of seagrass.
These turtles display high fidelity to specific foraging sites within seagrass beds, often returning to the same areas for sustenance. They primarily feed during the day, with some instances of nighttime feeding observed when light conditions are sufficient. The presence of healthy seagrass meadows and coral reef systems is important for their survival, as these environments provide both food and protection.