Hawaiian sea turtles are iconic inhabitants of the islands’ marine environment. Understanding what these reptiles consume provides insight into their lives. Their diets vary considerably among species and are fundamental to their survival.
Major Hawaiian Sea Turtle Species and Their Food
The green sea turtle, Honu, is the most frequently encountered sea turtle in Hawaiian waters and is primarily herbivorous as an adult. They graze on macroalgae (seaweed) and seagrasses in shallow coastal feeding grounds, which contributes to the green color of their body fat. This diet helps them thrive in nearshore habitats, including coral reefs.
Hawksbill sea turtles, Honuʻea, possess a narrow, hawk-like beak adapted for reaching into crevices on coral reefs. This allows them to primarily consume sponges, which are often difficult for other marine animals to access. Their diet can also include other invertebrates and marine algae if sponges are less available.
Loggerhead sea turtles, Akula, are primarily carnivorous as adults, utilizing powerful jaws and massive heads to crush hard-shelled prey. Their diet typically consists of bottom-dwelling invertebrates such as crabs, conchs, and clams. They also consume whelks and horseshoe crabs, showcasing their ability to handle robust shells.
Leatherback sea turtles, Ea, are unique for their diet, consisting almost exclusively of jellyfish and other soft-bodied invertebrates like tunicates and sea squirts. They possess sharp cusps on their jaws and downward-pointing spines (papillae) lining their throats, which help them pierce and hold onto slippery gelatinous prey. This allows them to efficiently consume large quantities of jellyfish.
Olive Ridley sea turtles, Wawali, exhibit an omnivorous diet, making them highly adaptable foragers. Their varied food sources include crabs, shrimp, spiny lobsters, and jellyfish. They also consume plant material such as algae, demonstrating broad dietary flexibility.
Dietary Changes Through Life Stages
A sea turtle’s diet changes significantly from hatchling to adult. Newly hatched sea turtles, regardless of species, begin life in the open ocean, a period often called the “lost years.” During this stage, hatchlings are opportunistic omnivores, feeding on a diverse array of small prey.
Their diet in the pelagic zone includes pelagic mollusks, larval crustaceans, hydrozoans, and fish eggs. They may also consume floating seaweed and small jellyfish. As they grow, juvenile turtles transition from this open-ocean diet to coastal areas, typically when they reach the size of a dinner plate.
For some species, like the green sea turtle, this transition involves a dramatic dietary shift. While green turtle hatchlings are omnivorous, they become primarily herbivorous adults, grazing on seagrass and algae in coastal habitats. This allows them to specialize in food sources abundant in their adult foraging grounds.
The Ecological Impact of Their Feeding Habits
The feeding habits of Hawaiian sea turtles play a significant role in maintaining marine ecosystem health. Green sea turtles, through their grazing on seagrass beds, act as “lawnmowers” of the sea. This prevents overgrowth, encouraging healthy seagrass growth and providing habitat and nursery for other marine species.
Hawksbill sea turtles contribute to coral reef vitality by consuming sponges. Sponges can outcompete corals for space, so hawksbills’ diet promotes coral growth and maintains reef diversity.
Leatherback sea turtles, by feeding on jellyfish, help regulate jellyfish populations. Unchecked jellyfish blooms can negatively affect fish stocks, so leatherback predation helps prevent an imbalance in the food web.