Undulated Moray

The Undulated Moray (Gymnothorax undulatus) is a widely distributed eel of the family Muraenidae, found across the tropical Indo-Pacific from the Red Sea and East Africa to Hawaii and the Pacific islands. It is one of the more frequently encountered morays on shallow reef flats and lagoons, reaching lengths of roughly 60-100 centimeters. As individuals mature, the head often lightens to a plain yellowish tone while the body retains its distinctive wavy markings. The species is common and not considered threatened, playing a role as a mid-level predator within reef food webs throughout its broad range.

Key features for identification:

• Pale cream to yellowish body covered in dark brown, undulating, maze-like markings that give the species its name
• Head often becomes plain yellowish with small black speckles in older adults, contrasting with the patterned body
• Moderate length, typically 60 cm to just over 1 m
• Continuous dorsal, caudal, and anal fins forming a single fringe
• Tubular anterior nostrils and a pointed snout It differs from the Yellow-edged Moray by its coarser, more irregular wavy bands (versus fine dense spotting) and lack of a yellow dorsal-fin edge.

Undulated Morays occupy shallow, wave-exposed reef flats, lagoons, and rocky intertidal pools across the tropical Indo-Pacific, typically in less than 20 meters of water though they range somewhat deeper on reef slopes. They favor holes and crevices in coral rubble, dead coral, and rocky substrate where they can retreat with only the head exposed. Their range extends from the Red Sea and East African coast across the Indian Ocean to Southeast Asia, Australia, Japan, and out to Hawaii and French Polynesia, making them among the most widespread morays in the region. They tolerate warm, well-oxygenated tropical waters and strong surge typical of shallow reef environments.

This species is solitary and strongly territorial, defending a favored den and rarely straying far from it during daylight hours. It is primarily nocturnal, emerging after dark to forage for fish and crustaceans, locating prey largely by scent rather than sight. Undulated Morays can be aggressive if their den is disturbed by divers or other reef animals and will often gape their jaws in a defensive threat display. Like other morays, they rely on a secondary pharyngeal jaw to draw prey into the digestive tract. Little is documented about their spawning, but as with related species, reproduction likely involves pelagic larval dispersal (leptocephalus stage) before settlement on reefs.