Leatherback sea turtles (Dermochelys coriacea) are the largest living turtles and the heaviest non-crocodilian reptiles. Some individuals exceed 2 meters (6.5 feet) in length and weigh over 900 kg (1,980 lbs). Unlike other sea turtles, they lack a hard, bony shell, possessing a carapace covered by tough, rubbery skin, which gives them their name. These turtles have existed in their current form since the age of the dinosaurs and undertake extensive migrations across the world’s oceans.
What They Primarily Eat
Leatherback sea turtles are specialized feeders, primarily consuming gelatinous zooplankton, with jellyfish making up most of their diet. This includes species like lion’s mane and moon jellyfish. Despite the low energy density of jellyfish, their abundance in certain ocean areas makes them a suitable food source for these massive creatures.
To sustain their large bodies and high metabolic rates, leatherbacks must consume enormous quantities of jellyfish. An adult leatherback can consume an average of 73% of its body mass in wet jellyfish daily, equating to hundreds of kilograms of food. This significant consumption highlights their adaptation to a low-nutrient food source.
Specialized Feeding Mechanisms
Leatherback sea turtles possess anatomical adaptations that enable their specialized diet. Their mouths have sharp-edged jaws and two pointed cusps on the upper jaw, which help them grasp slippery prey like jellyfish. These features are designed for handling soft-bodied organisms instead of teeth.
A key adaptation is the presence of hundreds of backward-pointing, keratinized spines, called esophageal papillae, lining their esophagus and throat. These papillae act like a one-way filter, ensuring ingested jellyfish cannot escape. They also protect the turtle’s throat from stinging cells and help push food towards the stomach while expelling excess seawater.
Diet-Related Threats and Ecological Importance
The specialized diet of leatherback sea turtles makes them vulnerable to environmental threats, especially plastic pollution. Floating plastic bags and other debris often resemble jellyfish, leading to accidental ingestion. Studies show over one-third of leatherback necropsies reveal ingested plastic, which can cause internal blockages or punctures, leading to death. Once ingested, the backward-pointing papillae in their throats make regurgitation nearly impossible.
Despite these threats, leatherbacks play an important role in marine ecosystems. As primary predators of jellyfish, they help regulate jellyfish populations. Their feeding habits maintain the balance of marine food webs, as unchecked jellyfish blooms can negatively affect other marine life, including fish. A decline in leatherback populations could disrupt these ecological balances.