A moray eel has a long, snake-like body and no scales, and moray eels live in tropical seas, on coral reefs and rocky reefs. Morays belong to the eel order Anguilliformes, which has more than 800 eel species worldwide as of November 2026, and as of November 2026, scientists count about 200 species of moray eel. A 2012 checklist of the world's moray eels recognizes 15 genera and two subfamilies. Morays range in length from about 20 centimeters, for the redface eel, to 3.75 meters, for the longtail moray, and the giant moray is reported to reach about 3 meters long. Scientists have studied morays with high-speed video, X-rays, bite measurements and field traps.

Fish swim like eels by bending the whole body into waves from side to side, and this is called anguilliform swimming. Morays have no paired fins, which means they have no pectoral fins and no pelvic fins, so they are not very stable, and it is not unusual to see one lying on its side or upside down. A moray can swim backward almost as well as forward, and this helps it back into a crevice. A fish's spine can be made longer by adding vertebrae at the front, adding them at the tail end, or making each vertebra longer, and morays have more vertebrae in the tail region of the spine than the other two major groups of eels. These extra tail vertebrae give morays enough length to tie an overhand knot with the body and use it as an anchor, and a moray can tie its body into a knot to get leverage when it eats.

A moray often hides in a crack in the rocks with only its head showing, and a giant moray lives alone in a hole in the reef. Giant morays live on reefs and in lagoons. Most moray eels hunt at night, and smell is a moray's strongest sense, so it uses smell to find food. A moray has tube-shaped nostrils on its snout that it uses to smell, and the giant moray has very poor eyesight and relies on its sense of smell to find food. A moray's lateral line pores are found only on the front part of the body.

Morays eat fish, octopuses and crustaceans, and studies of moray diets found they eat small fish, octopus, shrimp, and hard-shelled prey such as mollusks and crabs. Many moray eels have sharp teeth, and moray teeth point backward. Some morays have sharp, fang-like teeth and others have low, blunt teeth for crushing, and morays that eat fish have sharper teeth and longer skulls. Morays with blunt crushing teeth feed mostly on crustaceans, and zebra morays are thought to be the hallmark of durophagy, which means that their diet is mainly hard-shelled prey such as crabs and reef urchins. Researchers measured the bite force of 49 live California morays, each 567 to 1,192 millimeters long, and the bites ranged from about 32 to 467 newtons (N). In California morays, bite force grew faster than head size, so larger morays bite harder for their head and body size.

Most bony fish are suction feeders, and even the mudskipper, which takes prey on land, carries water in its mouth to use suction. Unlike many fish, a moray cannot pull in prey with strong suction. A moray has a second set of jaws in its throat, and high-speed video and X-rays showed that these throat jaws lunge forward into its mouth and pull prey into the throat. To see the pharyngeal jaws, which are the throat jaws, at work, UC Davis researchers took X-rays of eels eating dead goldfish. Rita Mehta was the first to video the moray's double jaws in action, as a postdoctoral researcher in Peter Wainwright's lab at UC Davis. The researchers in the 2007 Nature study found that the extendable jaws of morays are the first throat jaws known to be adapted to help catch prey, not just swallow it. A moray's two sets of jaws work like a double bite, which the Nature study compared to the way snakes swallow large prey in stages.

Before Mehta began studying California morays in 2010, no one thought many morays lived in the area. Mehta and Higgins trapped, examined and tagged 462 California morays at Two Harbors in just a few weeks. Over the years Mehta's team returned to their California moray field sites, they repeatedly trapped many eels in the same location, a tendency called site fidelity. To learn what morays eat, Mehta searched databases for reports on moray prey and catalogued stomach contents of museum specimens. The California moray eats small reef fish, octopuses, shrimps and crabs, and California morays at Catalina Island specialize on kelp bass as prey.

In the Red Sea, groupers and giant morays have been seen hunting together, and a grouper approaches a resting giant moray and shakes its head 3 to 6 times a second a few centimeters in front of it. Redouan Bshary of the University of Neuchatel and colleagues described this in the journal PLoS Biology in December 2006. In that study, groupers hunt by day in open water and giant morays are evasive nocturnal hunters, and both hunted more successfully when together than when hunting alone. Groupers signal to morays more often when the groupers are hungry, and the researchers concluded that giant morays broaden their hunting activity to daylight hours because of their interactions with groupers.

Morays lay eggs, and the eggs are fertilized outside the body. One published source recorded ripe green moray eggs measuring 1 millimeter across from a 1.1-meter female, while other sources suggest the eggs of other morays are 3 to 4 millimeters. A baby moray is a see-through, leaf-shaped larva called a leptocephalus, and muraenid leptocephali have pectoral fins that the adults lack, which are absorbed when the larva changes into a juvenile. A young moray first drifts in open water as a larva before it settles near the bottom, and spotted moray larvae can take up to a year to grow large enough to swim down to the reef.

A moray is a long, snake-like eel without scales, and its extra tail vertebrae let it tie a knot with its body. It often hides in a crack in the rocks, and most moray eels hunt at night, using smell to find food. It cannot pull in prey with strong suction, and it has a second set of jaws in its throat, which lunge forward to pull prey in. Scientists have studied morays with high-speed video, X-rays, bite measurements and traps, and they watched groupers and giant morays hunting together, where both hunted more successfully than they did alone.

Words to know

• crevice: narrow crack
• suction: pulling force
• larva: young form
• durophagy: shell-eating