Jellyfish are eaten by a surprisingly wide range of predators, from massive whales to tiny crabs. Despite being roughly 95% water and offering very little calorie density per bite, jellyfish are abundant, easy to catch, and quick to digest, making them a worthwhile meal for animals that have adapted to exploit them.
Sea Turtles, Especially Leatherbacks
Leatherback sea turtles are the most well-known jellyfish predators on the planet. These are the largest living turtles, reaching over 6 feet in length, and jellyfish make up the bulk of their diet. An adult leatherback can consume nearly its own body weight in prey each day, which for a 700- to 1,500-pound turtle means an enormous volume of jellyfish. Their throats are lined with backward-pointing spines that prevent slippery jellyfish from escaping once swallowed. Other sea turtle species eat jellyfish too, but none rely on them as heavily as leatherbacks do.
Ocean Sunfish
The ocean sunfish, or mola mola, has long been described as a dedicated jellyfish eater. It’s the heaviest bony fish in the world, sometimes exceeding 2,000 pounds, and was traditionally classified as an obligate jellyfish predator. More recent research using stable isotope analysis has complicated that picture. Smaller ocean sunfish (under about three feet long) appear to feed broadly within coastal food webs rather than relying exclusively on jellyfish. Larger adults do consume significant quantities of jellyfish and other gelatinous organisms, but the species is more of a generalist than scientists once thought.
Fish and Sharks
Several fish species regularly eat jellyfish. Grey triggerfish are among the more consistent jellyfish predators, using their tough mouths to bite through the gelatinous tissue without being deterred by stinging cells. Whale sharks, the largest fish alive, filter-feed on jellyfish along with plankton and small fish. Various species of tuna, swordfish, and butterfish have also been documented eating jellyfish when the opportunity arises, though for most of these fish, jellyfish are a supplement rather than a staple.
Seabirds
Northern fulmars are among the most enthusiastic bird predators of jellyfish. In studies of fulmar stomachs, jellyfish remains showed up in more than 40% of the birds examined. Researchers observing fulmars in the Barents Sea found that the birds feed from the underside of lion’s mane jellyfish, selectively eating the energy-rich gonadal tissue, oral arms, and tentacles while ignoring the watery umbrella (the bell). This selectivity is a smart strategy: rather than filling up on tissue that is almost entirely water, the birds target the parts with the most nutritional payoff.
Whales and Crabs
Humpback whales eat jellyfish, likely scooping them up incidentally while filter-feeding but also consuming them deliberately when they’re plentiful. On the smaller end of the spectrum, arrow crabs and hermit crabs scavenge on jellyfish tissue. For crabs, a beached or weakened jellyfish is an easy, low-risk meal since the crab’s exoskeleton provides protection from stinging cells.
Other Jellyfish
Some of the most effective jellyfish predators are other gelatinous organisms. Comb jellies of the genus Beroe specialize in eating other jellies, including invasive species. In the Black Sea during the 1990s, the arrival of Beroe ovata helped control a population explosion of the invasive comb jelly Mnemiopsis leidyi that had devastated local fisheries. The fried egg jellyfish is another species known to prey on smaller jellies it encounters while drifting.
Why Predators Bother With Such Watery Prey
Jellyfish are between 95% and 98% water by weight, which makes them one of the least calorie-dense foods in the ocean. On a dry weight basis, they do contain meaningful protein (roughly 20% to 54%) and minerals (16% to 57%), but very little fat. Their energy content ranges from about 1 to 5 calories per gram of dry weight, which is modest compared to fish or squid.
So why do so many predators eat them? Three reasons stand out. First, jellyfish are extremely easy to catch. They can’t flee, fight back effectively, or hide. The energy an animal spends catching a jellyfish is almost nothing compared to chasing a fish. Second, jellyfish digest rapidly, so a predator can eat continuously and process large volumes in a short time. Third, jellyfish are increasingly abundant in many ocean regions, sometimes forming dense blooms that offer a nearly limitless food supply for any animal willing to eat them. Predators that selectively feed on the most nutritious parts, the way fulmars target gonads and oral arms, get even more value per meal.
Humans as Jellyfish Predators
People have eaten jellyfish for over a thousand years, primarily in East and Southeast Asia. Species like the cannonball jellyfish are harvested commercially, processed with salt and alum to remove water, and served in salads, soups, or as a crunchy side dish. Prepared cannonball jellyfish contains about 95% water and 4% to 5% protein, with very few calories and almost no fat or cholesterol. The global jellyfish fishery has grown in recent decades as traditional fish stocks decline and demand for low-calorie, high-protein foods rises.