Giant Oceanic Manta Ray Facts

An adult spans 11 to 23 feet across the wings and weighs 1,500 to 4,000 pounds, its skeleton made entirely of light, flexible cartilage rather than bone. The signature features are the two fleshy cephalic lobes projecting from the head — rolled into spirals to cut drag when cruising (the "horns" that earned mantas the name "devil fish"), and unfurled into funnels when feeding to guide plankton-rich water into the wide mouth. Inside, cartilaginous gill rakers strain out the tiny prey as water passes through the gills. The ray is strongly countershaded — dark above to vanish against the deep, white below with a unique pattern of black spots that lets researchers identify individuals. It belongs to the devil-ray family Mobulidae; its ancestors abandoned the seafloor for open water and lost the venomous tail spine of their stingray relatives, their pectoral fins becoming muscular wings for efficient gliding.

The giant manta ranges around the globe through tropical, subtropical, and temperate seas of the Atlantic, Pacific, and Indian Oceans, recorded as far north as New Jersey and southern California and as far south as New Zealand and South Africa. Unlike the coastal reef manta, it is deeply pelagic and highly migratory, spending most of its life in open water following the upwellings, current convergences, and seamounts that concentrate zooplankton, and only periodically gathering at offshore islands and reefs to visit cleaning stations or exploit seasonal feeding.

As an obligate filter feeder, the manta sits low on the food chain, living on zooplankton — krill, mysids, copepods, small shrimp, and the larvae of fish and crabs. Because plankton is patchy, mantas use specialized tactics to concentrate their intake. The most spectacular is the "barrel roll," in which the ray loops backward in tight vertical somersaults to stay inside the densest patch while water pours through its gills. Feeding in groups, they may form a "cyclone," swimming in a coordinated chain that spins a vortex drawing plankton to the center so dozens can feed at once.

Often solitary at sea, giant mantas become social at food sources and reef cleaning stations — coral outcrops staffed by cleaner wrasses that the ray lets swim into its mouth and over its gills to pick off dead tissue and parasites, a partnership vital to its health. Mantas have the largest brain-to-body ratio of any cold-blooded fish, complete with a network of vessels that warms the brain, and they show intense curiosity toward divers, often altering course to investigate bubbles. They also breach, launching their whole body clear of the water to land with a thunderous slap — perhaps to shed parasites, to signal, or simply in play.

The giant manta is extraordinarily slow to reproduce. Females don't mature until 8 to 10 years old, and mating is energetic — a "mating train" of males pursuing one female, each trying to grip her pectoral fin. Mantas are ovoviviparous: the embryo hatches from its egg inside the mother and is nourished first by a yolk sac and then by enriched uterine "milk," through a gestation of about 12 to 13 months. The mother bears a single, fully independent pup in shallow coastal water — already 4 to 5 feet across and up to 20 pounds — that swims off with no further care. A female may produce only 4 to 6 pups in a 40-year life, which makes the species exceptionally slow to recover.

The giant oceanic manta is Endangered, declining sharply worldwide. The gravest threat is targeted fishing for its gill rakers, dried and sold mainly in Asia for unproven traditional remedies; slow-swimming and gathering in predictable places, mantas are easily taken with harpoons and gillnets, and their size makes them frequent fatal bycatch in tuna nets, longlines, and ghost gear. Microplastic pollution is an insidious added threat, since filter feeders ingest plastic particles as they forage. CITES Appendix II trade controls and large marine protected areas in places like Indonesia, the Maldives, and Ecuador are central to pulling the species off its extinction path.

• NOAA Fisheries: Giant Manta Ray Species Profile
• IUCN Red List of Threatened Species: Mobula birostris