Giant Manta Ray (Mobula birostris): Facts, Size and Diet

What is a giant manta ray?

Manta rays are cartilaginous fish, related to sharks, and belong to the order Myliobatiformes, the stingrays and their relatives. They evolved from bottom-dwelling stingrays but became open-water swimmers and filter feeders. Together with the smaller devil rays, they form the family Mobulidae.

For a long time, all mantas were treated as one species. In 2009, marine biologist Andrea Marshall and colleagues showed that there are two: the larger, ocean-going giant manta (M. birostris) and the smaller, more coastal reef manta (M. alfredi). Genetic studies then showed that mantas sit inside the devil ray genus Mobula, so in 2017–2018 the genus Manta was merged into Mobula. In 2025, a third species, the Atlantic manta (Mobula yarae), was formally described from the western Atlantic.

Appearance

A giant manta has a broad, flattened, diamond-shaped body with long, pointed pectoral fins that it flaps like wings. In front of the wide, rectangular mouth, which sits at the very front of the head, are two cephalic fins. They are rolled up into horn-like spirals while swimming and unfurled to funnel food into the mouth during feeding. These “horns” earned mantas the old nickname devilfish. The eyes are on the sides of the head, the gill slits are on the underside, and behind the small dorsal fin is a whip-like tail with a small, harmless knob or spine, a leftover of the stinging barb of its stingray ancestors.

Most giant mantas are “chevron” colored: black or dark gray above, with two white shoulder patches separated by a dark band that forms a T shape, and white below. The mouth is usually dark, and dark spots are clustered on the lower belly. A minority are almost completely black. The pattern of spots on each manta’s belly is unique, like a fingerprint, and researchers use photos of it to identify individuals.

The skin feels rough because it is covered in tiny tooth-like scales called denticles, and it is coated in a protective layer of mucus.

How big is the giant manta ray?

Giant mantas are measured by their disc width, from wingtip to wingtip. Typical adults are about 4–5 m (13–16 ft) across, and the largest reliably reported reach about 7 m (23 ft). NOAA Fisheries gives a maximum of about 8 m (26 ft), and older claims of 9 m (30 ft) are not confirmed. Large adults weigh well over 1,000 kg (2,200 lb), and the heaviest are estimated at about 2,000–3,000 kg (4,400–6,600 lb).

Only a few fish, mainly the whale shark and the basking shark, are clearly bigger; see the largest fish in the world. The reef manta is usually 3–3.5 m (10–11.5 ft) wide, with a maximum of about 5.5 m (18 ft). More comparisons are in how big is a manta ray?

Habitat and range

The giant manta lives in tropical, subtropical and warm temperate seas around the world, mostly in water of about 19–30 °C (66–86 °F). It has been recorded as far north as southern California, New Jersey, northern Japan and the Azores, and as far south as Peru, Uruguay, South Africa and New Zealand. In the western Atlantic, including the Gulf of Mexico and the Caribbean, many mantas once identified as giant mantas are now thought to belong to the newly described Atlantic manta.

It is an ocean wanderer that spends much of its life far from land, but it visits coastlines, offshore islands and seamounts where currents bring cold, nutrient-rich water up from the deep. Tagged giant mantas have traveled as far as about 1,000 km (620 mi) and dived deeper than 1,000 m (3,300 ft). The largest known population, estimated at more than 22,000 animals, lives off Ecuador, including Machalilla National Park and the Galápagos. Most other regional populations studied are small, from about 600 to 2,000 individuals.

What do giant manta rays eat?

Giant mantas are filter feeders. They eat zooplankton, such as krill, copepods, mysid shrimp and the larvae of crabs and shrimp, as well as small fish. While feeding, a manta swims slowly with its mouth wide open and its cephalic fins spread, channeling water through its gills. Spongy, pinkish-brown filter plates between the gill arches trap the food while the water flows out through the gill slits.

Mantas use several feeding styles. They may swim in straight lines through dense patches of plankton, turn repeated backward somersaults in one spot, or line up nose to tail with other mantas in feeding chains. At the surface they look like pure plankton eaters, but a 2016 study of chemical markers in the tissue of giant mantas off Ecuador suggested that much of their diet comes from deeper water, where they may feed out of sight.

Behavior and intelligence

Giant mantas usually travel alone, but they gather in groups of up to about 50 at rich feeding sites, at cleaning stations and during the mating season. At cleaning stations on reefs, a manta hovers for several minutes while small cleaner fish, such as wrasses, pick parasites and dead skin from its body and gills. Individual mantas return to the same cleaning stations again and again, which suggests a good memory for places.

Mantas have the largest brain of any fish and one of the highest brain-to-body ratios. A network of blood vessels around the brain, called a rete mirabile, helps keep it warmer than the surrounding water during deep dives. In a 2016 study, two captive giant mantas behaved unusually in front of a mirror, repeatedly moving as if checking their reflection, which some researchers see as a hint of self-awareness. The meaning of this result is still debated.

Mantas sometimes leap clear of the water and land with a huge splash. Nobody knows exactly why; the leading ideas are explored in why do manta rays jump?

Reproduction and life cycle

Giant mantas reproduce very slowly. Males mature at a disc width of about 4 m (13 ft) and females at about 4–5 m (13–16 ft), and female mantas are thought to reach maturity at around 8–10 years old or later. During courtship, a female may be followed by a “train” of several males. A male grips the tip of her pectoral fin in his mouth, turns belly to belly with her, and inserts one of his two claspers to fertilize her eggs internally.

The pup develops inside the mother for about a year. It first feeds on egg yolk, then on a milky fluid produced by the wall of the uterus. Usually just one pup is born, rarely two, and it already measures roughly 1.1–1.4 m (3.6–4.6 ft) across. Young mantas often stay in shallow, protected coastal waters for their first years. Females usually give birth only once every two to three years, so each female produces relatively few pups in her lifetime.

Giant mantas are long-lived. NOAA reports that they live at least 45 years.

Predators and threats

Because of their size and speed, adult mantas have few natural enemies. Large sharks, such as tiger sharks, great hammerheads and bull sharks, as well as orcas and false killer whales, can kill them, and many adults carry scars from shark bites.

People are a much greater threat. In recent decades, demand for manta and devil ray gill plates, sold dried in parts of Asia as a remedy with no proven health benefit, has driven targeted fisheries in countries such as Indonesia, Sri Lanka, India and the Philippines. Mantas are also caught as bycatch in gillnets, purse seines, longlines and trawls. Because they must keep swimming to breathe and cannot swim backward, they easily become tangled in fishing lines and nets. Boat strikes, plastic pollution and climate change add to the pressure.

Conservation status

The IUCN Red List classified the giant oceanic manta ray as Endangered in 2020, with a decreasing population. Some regional populations have fallen sharply where they are fished, and the slow breeding rate means they recover only over decades.

Mantas have gained protection in recent years. The giant manta was added to the Convention on Migratory Species in 2011 and to CITES Appendix II, which controls international trade, in 2013. In 2018, the United States listed it as threatened under the Endangered Species Act. Countries including Ecuador, Mexico and Indonesia ban fishing for mantas, and Hawaii banned killing or capturing mantas in 2009.

Manta rays and people

Mantas were once feared. Sailors believed they could drag boats out to sea or wrap themselves around divers. Since the 1970s, divers have shown that mantas are gentle and often curious, and today they are among the most sought-after animals in diving and snorkeling. Manta tourism is worth tens of millions of US dollars a year, so a living manta is worth far more to local communities than a dead one. They pose no real threat to people, as explained in are manta rays dangerous?

Divers can help by following simple rules: keep a respectful distance, never touch or chase a manta, and stay clear of cleaning stations. Mantas are also often confused with stingrays, although the two live very different lives; see manta ray vs stingray.