What Eats a Leatherback Sea Turtle? A Predator Breakdown

Leatherback sea turtles face a rotating cast of predators throughout their lives, though the threats shift dramatically depending on life stage. Eggs and hatchlings are vulnerable to everything from ghost crabs and rats to fungal infections, while adults in the open ocean contend mainly with large sharks. The leatherback’s massive size offers real protection once it reaches maturity, but the journey from egg to adult is a gauntlet that relatively few individuals survive.

What Raids the Nest

A leatherback nest, buried roughly half a meter down in warm sand, contains around 80 fertilized eggs along with a number of smaller, yolkless “spacer” eggs. That clutch is a protein-rich target for a surprising variety of animals. A global review of sea turtle nest predation identified 36 species that dig into nests, about 30 of them native and 8 invasive. Ghost crabs, coconut crabs, black rats, feral pigs, monitor lizards, and raccoons all make the list.¹ The method is often the same: the predator tunnels obliquely into the sand until it reaches the egg chamber, then feeds in place or hauls eggs to the surface.

Ghost crabs and black rats are among the most widespread nest raiders. Ghost crabs are native to tropical beaches worldwide and dig their own burrows close to the high-tide line, making sea turtle nests convenient neighbors. Black rats, by contrast, are an invasive species on many nesting beaches, introduced through shipping centuries ago and now established on coastlines and islands from the Caribbean to Southeast Asia. Feral dogs and pigs pose a more localized but intense problem on beaches where they roam freely; a single feral pig can destroy multiple nests in a night.

Across all causes, roughly 65% of sea turtle eggs hatch successfully. Direct predation accounts for about 3% of egg losses, while a much larger share, around 18%, die during incubation from causes unrelated to predators, including flooding, root intrusion, and temperature extremes.¹ That 3% figure may seem small in a global average, but it masks enormous variation from beach to beach. On islands with dense rat populations or uncontrolled feral animals, predation rates can be many times higher.

Fungus in the Sand

Not all egg threats have legs. A fungal disease called sea turtle egg fusariosis, caused by species in the genus Fusarium, has emerged as a serious conservation concern. Two species in particular are implicated. Surveys of eggshells and nest sand at four major nesting beaches along both coasts of Costa Rica found that about a third of fungal cultures isolated belonged to these two species, and one of them turned up at every study location on both the Pacific and Caribbean coasts.²

Leatherback nests appear especially susceptible. Research on nesting beaches in southeast Florida found Fusarium present in leatherback nests and documented mycotic dermatitis, a fungal skin infection, in both dead and live captive leatherback hatchlings that had recently emerged.³ That finding is striking because it suggests the fungus does not just kill embryos inside the egg. It can colonize the nest environment and infect hatchlings as they crawl through contaminated sand on their way out. Whether fusariosis is genuinely increasing or simply being detected more frequently with better surveillance is still debated, but it has become a front-burner topic for turtle biologists working on nesting beaches.

The Hatchling Gauntlet

Emerging from the nest is only the beginning of the danger. Leatherback hatchlings weigh about 40 to 50 grams and measure roughly 6 centimeters in length. They typically emerge at night, which helps them avoid some visual predators, but plenty of threats operate in darkness or wait until dawn.

On the beach itself, ghost crabs are a major hatchling predator. They are fast, nocturnal, and abundant on the same stretches of sand where turtles nest. Raccoons, coatis, and feral dogs will also snatch hatchlings making their dash to the waterline. Artificial lighting near nesting beaches compounds the problem by disorienting hatchlings, causing them to wander inland instead of toward the ocean, which extends their exposure time on land.

Once in the water, hatchlings enter what biologists sometimes call the “lost years,” a poorly understood period of open-ocean drifting during which they remain small enough to be eaten by a wide range of predatory fish. Large pelagic species, including dorado, tuna, and billfish, are known to take small turtles near the surface. Seabirds such as frigatebirds and gulls also pick off hatchlings in the surf zone and shallow nearshore waters. The cumulative mortality during this early phase is enormous. By some estimates, only one in a thousand sea turtle hatchlings survives to reproductive age, though precise figures for leatherbacks specifically are hard to pin down because tracking tiny animals across open ocean for years is extraordinarily difficult.

Sharks and Other Open-Water Predators

As leatherbacks grow, the list of animals capable of killing them shrinks rapidly. An adult leatherback can reach well over 500 kilograms and stretch nearly two meters in shell length. At that size, the number of marine predators with both the motive and the equipment to attack becomes very short.

Tiger sharks and great white sharks are the only two species reliably confirmed as predators of sea turtles at sea. A large-scale analysis of over 156,000 turtle records, both live sightings and dead recoveries, found that about 3.3% showed evidence of shark-bite injuries. Stomach-content analysis of nearly 4,000 sharks from 12 species found turtle remains only in tiger sharks and white sharks, with tiger sharks emerging as the dominant predator.⁴

Tiger sharks are well suited to the task. Their teeth are broad, heavily serrated, and curved in a way that lets them saw through hard surfaces, an adaptation thought to have evolved in part for dealing with turtle shells. White shark teeth are built differently, designed to penetrate and cut with enormous force, and the leatherback’s carapace would not prevent a determined attack.⁴ That said, leatherbacks may not be a preferred target for white sharks. Most documented white shark interactions with leatherbacks come from bite-scarred carcasses washing ashore rather than from direct observation of predatory attacks, leaving open the question of whether some of those bites were scavenging on already-dead turtles.

Orcas are occasionally reported attacking leatherbacks, though documented cases are rare. Given the orca’s size, intelligence, and ability to take large marine prey, it would be surprising if they never targeted leatherbacks, but the interaction does not appear to be a common or important source of mortality for the species. Smaller sharks, despite sharing the ocean with leatherbacks, simply lack the jaw gape and bite force needed to tackle an animal that large.

Jaguars on the Nesting Beach

One of the more dramatic predator-prey interactions involving leatherbacks happens on land. In parts of Central and South America, jaguars patrol nesting beaches at night and kill adult female turtles as they come ashore to lay eggs. Tortuguero, on Costa Rica’s Caribbean coast, is one of the best-studied sites for this behavior. Research there found that jaguars consumed an average of about two leatherbacks per year, a small number compared to the roughly 120 green turtles taken annually at the same beach.⁵

Why the difference? Part of it is timing and numbers. Green turtles nest in far greater abundance at Tortuguero than leatherbacks do, so jaguars encounter them more often. Leatherbacks are also considerably larger and more difficult to subdue. A jaguar typically kills a sea turtle by biting through the skull or the soft tissue at the base of the neck, and a full-grown leatherback’s size makes that a more challenging proposition than with a green turtle.

The researchers concluded that jaguars do not represent a meaningful population-level threat to the green turtles nesting at Tortuguero, and are not the main cause of population decline for leatherbacks or hawksbills either.⁵ That framing matters for conservation. Jaguar predation on sea turtles sometimes generates alarm in local communities, but the evidence suggests it is a natural ecological interaction that the turtle populations can sustain. The forces actually driving leatherback declines are elsewhere.

How Leatherbacks Protect Their Nests

Leatherbacks are not passive about nest defense. They cannot guard their eggs after returning to the sea, but they invest heavily in concealment before they leave the beach. After depositing her eggs and filling the nest cavity, a female leatherback enters an elaborate sand-scattering phase. She does not simply pack down the sand and go. She follows convoluted paths across the beach, flinging sand with her flippers and disturbing a large area around the nest site.

Tracking studies found that nesting leatherbacks disturbed an average of about 30 square meters of beach surface during this phase, with some individuals churning up nearly 60 square meters. The center of the disturbed area was always offset from the actual nest location, and in none of 26 observed nestings did the female’s path pass directly over her own eggs.⁶ The pattern is consistent with active decoy behavior: by creating a wide zone of disrupted sand centered somewhere other than the clutch, the female makes it harder for a visual or olfactory predator to locate exactly where the eggs are buried.

This is a substantial energy expenditure for an animal that may nest several times in a season and does not eat during the nesting period. The fact that leatherbacks invest so much in camouflaging suggests that nest predation has been a strong selective pressure throughout their evolutionary history. For a species whose lineage stretches back over 100 million years, the strategy has clearly worked well enough in the context of natural predators. The question is whether it can also protect against human egg collection, which remains a problem on some beaches.

Why the Leatherback’s Shell Is Different

Unlike every other sea turtle species, leatherbacks do not have a hard, bony shell. Their carapace is a flexible, rubbery structure made of a matrix of connective tissue over a mosaic of tiny bone fragments called osteoderms, covered by a layer of tough, oil-saturated skin. This gives them a streamlined, hydrodynamic body shape that aids deep diving and long-distance swimming, and they need every bit of that efficiency: leatherbacks undertake some of the longest migrations of any reptile, crossing entire ocean basins between feeding and nesting grounds.

The trade-off is reduced armor. A hard-shelled turtle like a loggerhead or green turtle can retract somewhat into its shell, and the shell itself can deflect glancing bites from smaller sharks. A leatherback’s flexible carapace offers less mechanical protection, which may be part of why tiger sharks, whose teeth are specialized for cutting tough material, are the most frequently identified turtle predator at sea. On the other hand, the leatherback compensates with sheer size. Very few marine predators can grapple with an animal that weighs as much as a large horse. The leatherback also has an unusually thick layer of subdermal fat, which helps with thermoregulation in cold water but may incidentally make it harder for a shark to inflict a quickly fatal wound.

Bycatch and the Scale of Human-Caused Mortality

Natural predation, from crabs raiding nests to tiger sharks attacking adults, is part of the ecological context leatherbacks evolved within. These pressures shaped the species’ reproductive strategy: large clutches, multiple nesting events per season, and the decoy behavior described above. What leatherbacks did not evolve to withstand is industrial fishing.

Both Pacific leatherback populations are classified as critically endangered, and the primary driver is incidental capture, or bycatch, in both small-scale and industrial fisheries.⁷ Leatherbacks are particularly vulnerable to longline fisheries targeting tuna and swordfish, as well as gill nets. They become entangled, cannot surface to breathe, and drown. They also ingest hooks baited for other species. The scale is difficult to quantify precisely because observer coverage on many fishing fleets is estimated at less than 1%, meaning the vast majority of bycatch events go unrecorded.⁷

This context matters when thinking about natural predators. A jaguar taking two nesting females a year at one beach, or sharks biting a few percent of turtles they encounter at sea, are pressures the population can absorb. They always have. The problem is additive mortality from human activity stacking on top of natural losses. When adult survival drops even modestly because of bycatch, the math breaks down for a species that takes decades to reach sexual maturity and depends on high adult survivorship to maintain population numbers. The eggs eaten by ghost crabs are ecologically normal. The nets are not.

Plastic and the Jellyfish Problem

Leatherbacks feed almost exclusively on jellyfish and other soft-bodied gelatinous animals. Their esophagus is lined with backward-pointing spines that help grip slippery prey, and they lack the crushing jaw plates found in turtles that eat crabs or shellfish. This dietary specialization creates a unique vulnerability: floating plastic bags and film look remarkably similar to jellyfish when drifting in the water column.

Ingested plastic can obstruct the gut, reduce the animal’s ability to absorb nutrients, and in some cases cause internal injuries that lead to death. While plastic ingestion is not predation in any traditional sense, it functions as a mortality source that interacts with the same population dynamics affected by natural predators and bycatch. A leatherback weakened by partial gut obstruction from plastic may be slower and less able to evade a shark, or may arrive at a nesting beach in poorer body condition, laying fewer or smaller eggs. The intersection between pollution and predation vulnerability is not well quantified, but the dietary specialization that makes leatherbacks effective jellyfish hunters also makes them disproportionately susceptible to marine debris compared to turtles with more varied diets.

Conservation efforts aimed at leatherback predation rarely focus on the natural predators themselves. Rats can be controlled on critical nesting islands, and feral animals can be excluded from beaches with fencing, but the far larger challenge is reducing bycatch in international waters where enforcement is weak and fishing fleets operate across jurisdictional boundaries. The gap between what kills leatherbacks in nature and what is actually driving the species toward extinction is wide, and the predator breakdown across their life stages helps explain why: natural predation is something their biology accounts for, while industrial-scale threats are not.