Manta Ray; Characteristics, Species, Behavior, Feeding | Sea Life, Islands and Oceania

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MANTA RAYS

Reef manta ray (Manta alfredi) in Thailand

Once referred to as devil fish and first described in 1798, manta rays are docile, plankton-eating fish with a wing span of up to seven meters (23 feet) and can weigh 2400 kilograms (5,300 pounds). The world’s largest rays, they are found in tropical and sometimes warm temperate waters. Little is known about their breeding habits and life span. Scientist aren't even sure how many species there are. [Source: David Doubilet, National Geographic, December, 1995]

The lifespan of manta rays in the wild is 25 to 30 years. Although manta rays have been reported to live at least 40 years, not much is known about their growth and development. Re-sightings of individuals (identified by unique patterns of spots around their gill slits) have been recorded for spans of up to thirty years. While mortality rates are high among juveniles, adult mortality is low, probably due to their large size and a lack of predators. [Source: Kourtney Simpkins, Animal Diversity Web (ADW) /=]

Mantas have few natural predators except perhaps large sharks and orcas (killer whales). Occasionally mantas are spotted with shark bite marks. The relatively large number of scars found on juveniles compared to adults suggests that they endure more frequent attacks due to their smaller body size. Remoras often accompany manta rays, inside their mouths or clinging to their pectoral fins.. Because reef manta rays have the capacity to consume large quantities of plankton, they may have a top-down effect on the structure of the marine communities that they inhabit.

Websites and Resources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Fishbase fishbase.se ; Encyclopedia of Life eol.org ; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems

Manta Ray History

While some small teeth have been found, few fossilized skeletons of manta rays have been discovered. Their cartilaginous skeletons do not preserve well, as they lack the calcification of the bony fish. Only three sedimentary beds bearing manta ray fossils are known, one from the Oligocene (33.9 million to 23 million years ago) in South Carolina and two from the Miocene (23 million to 5.3 million years ago) and Pliocene (5.4 million to 2.3 million years ago) in North Carolina.

Giant oceanic manta ray (Manta birostris) at a cleaning station

Manta rays belong to the subfamily Mobulinae, which some suggest are the most morphologically advance and most highly evolved of all living sharks and rays (elasmobranch fishes). Bruce Barcott wrote in National Geographic, “Generations ago those hornlike cephalic fins earned mantas the name devilfish. Their terrifying size and bat shape fed an aura of mystery and menace, and mantas were vilified as ferocious monsters. That changed in the 1970s, when scuba divers found mantas to be gentle creatures. Sometimes they even permitted humans to catch joyrides on their broad backs. [Source: Bruce Barcott, National Geographic, July 2009]

Scientific knowledge about mantas remains surprisingly thin. In 2008, a leading expert proposed splitting the species in two: smaller resident mantas...that remain near shore, and larger transient mantas that roam the world's tropical and semitropical oceans. And researchers are just beginning to learn more about those cephalic fins. "When you approach a manta, it will unroll a cephalic fin and wave it back and forth as if it's scanning," says Robert Rubin, a California-based marine biologist who's studied mantas in Mexico for decades. "Mantas are essentially flat sharks, and we know some sharks have electrical receptors in their faces. The hypothesis is that mantas use those fins to pick up electrical signals from other animals moving in the water."

Manta Ray and Mobula Species

There are two species of manta rays: 1) giant manta rays (Manta birostris) and 2) reef manta rays (Manta alfredi). Giant manta rays are generally larger than reef manta rays, have a caudal thorn, and rough skin appearance. They can also be distinguished from reef manta rays by their coloration. Reef manta ray (Manta alfredi) are also known as Alfred manta, Inshore manta ray; Manta ray and Prince Alfred's ray). They range in length from 150 to 550 centimeters (59.06 to 216.54 inches). /=\ [Source: NOAA]

Munk's devil ray (Manta munkiana) breaching

Manta rays belong to the mobula family. There are eight mobula species:
1) Giant oceanic manta ray (Manta birostris)
2) Reef manta ray (Manta alfredi)
3) Devil fish (Manta mobular)
4) Lesser devil ray (Manta hypostoma)
5) Munk's devil ray (Manta munkiana)
6) Shortfin devil ray (Manta kuhlii)
7) Bentfin devil ray (Manta thurstoni)
8) Chilean devil ray (Manta tarapacana)

The Giant manta ray is also known as the giant oceanic manta ray. It is the world’s largest ray with a wingspan of up to nine meters (29 feet). They are filter feeders and eat large quantities of zooplankton. Giant manta rays are slow-growing, migratory animals with small, highly fragmented populations that are sparsely distributed across the world. These fish reach seven meters (23 feet), can weigh 2400 kilograms (5,300 pounds) and live to be 40 years old. In U.S. waters they can be found off New England, the Mid-Atlantic, Pacific Islands, and the Southeast [Source: NOAA]

A 2009 study — that analyzed the differences in morphology, including color, meristic variation, spine, dermal denticles (tooth-like scales), and teeth of different populations — found there are two distinct species: 1) the more coastal M. alfredi found in the Indo-Pacific and tropical East Atlantic, and 2) the larger, open-ocean M. birostris found throughout tropical, subtropical and warm temperate oceans. A 2010 study on mantas around Japan confirmed the morphological and genetic differences between M. birostris and M. alfredi. A third possible species, preliminarily called Manta sp. cf. birostris, reaches at least 6 meters (20 feet) in width, and inhabits the tropical West Atlantic, including the Caribbean. [Source: Wikipedia]

Munk's devil ray (Scientific name: Mobula munkiana) are also known as manta de monk, mobula rays pygmy devil ray, smoothtail mobula and Munk’s pygmy devil ray. Known for forming massive schools with thousands of members and leaping three meters (10 feet) out of the water, they are is found in tropical parts of the eastern Pacific Ocean, ranging from the Gulf of California to Peru, as well as near offshore islands such as the Galapagos and Cocos islands. The species was first described in 1987 by the Italian ecologist Giuseppe Notarbartolo di Sciara and named for his scientific mentor, Walter Munk. See Mobula Rays Under Ray Species ioa.factsanddetails.com

Habitat and Where They Are Found

range of Giant oceanic manta ray (Manta birostris)

The giant manta ray is found worldwide in tropical, subtropical, and temperate bodies of water and is commonly found offshore, in oceanic waters, and in productive coastal areas. The species has also been observed in estuarine waters, oceanic inlets, and within bays and intercoastal waterways. As such, giant manta rays can be found in cool water, as low as 19°C (66̊F) , although temperature preference appears to vary by region. For example, off the U.S. East Coast, giant manta rays are commonly found in waters from 19̊ to 22°C (66̊ to 72̊F) , whereas those off the Yucatan peninsula and Indonesia are commonly found in waters between 25̊ to 30°C (77̊ to 86̊ F) .[Source: NOAA]

Reef manta rays live in tropical, marine environments. You can typically find them in reefs or other coastal areas (within a few kilometers of land) in tropical and subtropical latitudes. They are often sighted near coral and rocky reefs in atolls and bays, likely due to the high densities of zooplankton associated with these areas. [Source: Kourtney Simpkins, Animal Diversity Web (ADW) /=]

Reef manta rays are found primarily in the Indian and Pacific Oceans, including coastal waters surrounding Australia, Japan, South Africa, Thailand and Hawaii, as well as the Red Sea. Although they have been found in the Atlantic Ocean, such sightings are rare. While it is known that they tend to avoid deep or open waters, the exact depth range in which they can be found has not been ascertained. /=\

Manta rays are regularly seen off Yap, a north Pacific island in Micronesia; off the Kona Coast of Hawaii; and near San Benedicto, one of the Revillagigedo Islands, 400 kilometers (250 miles) south of Mexico's Baja, California. Yap is one of the few places in the world where manta rays are encountered on nearly a daily basis. In the winter the manta rays come to Manta Ridge in Mili Channel for cleaning. Divers usually hold on to a ledge 30 feet below the surface and watch them cruise by. It is not unusual for divers to see six or seven manta rays at one time. In Hawaii, boats sometimes use light to attract clouds of plankton, which in turn attract manta rays.

Manta Ray Characteristics

Manta anatomy

Manta rays are recognized by their large diamond-shaped body with elongated wing-like pectoral fins, ventrally-placed gill slits, laterally-placed eyes, and wide, terminal mouths. In front of the mouth, they have two structures called cephalic lobes which extend and help to channel water into the mouth for feeding activities (making them the only vertebrate animals with three paired appendages or limbs). Manta rays are cold blooded (ectothermic, use heat from the environment and adapt their behavior to regulate body temperature). They have only a short tail with no fins or poisonous barb.[Source: NOAA]

Manta rays’ two long, mobile, cephalic fins can be rolled into a spiral while swimming or extended like a funnel to guide planktonic organisms into the ray’s mouth. Mantas take in water through their mouths and filter out organisms with a highly developed branchial sieve. Their mouths are large and terminal or subterminal, and they have very small, cuspidate or flat-crowned teeth. [Source: Monica Weinheimer and R. Jamil Jonna, Animal Diversity Web (ADW) /=]

Manta rays come in two distinct color types: chevron (mostly black back and white belly) and black (almost completely black on both sides). They also have distinct spot patterns on their bellies that can be used to identify individuals. Reef manta reefs are black in color on their back side and and cream or white colored on the bottom. Light colored patches can be found on the shoulder area, contrasting with the overall dark dorsal surface.

According to Animal Diversity Web: Reef manta rays have cephalic fin tips, or horns, that wrap around the mouth. Their central body disc is approximately two times longer than it is broad, with an average width of approximately 3.9 meters (12.8 feet) for adult females and three meters (10 feet) for adult males. The largest recorded specimen measured 5.5 meters (18 feet) in width. This is much smaller than giant manta rays which seldom smaller than 5.5 meters at maturity. Reef manta rays have a slender tail, with no distinct caudal spine. Females are larger than males. [Source: Kourtney Simpkins, Animal Diversity Web (ADW) /=]

Both the dorsal and ventral surfaces are covered in knob-like denticles, which are evenly distributed; ventral denticles are larger. They have a total of 918-1456 small, cusped teeth, which are each 1-2 millimeters in length. It is hypothesized that they have retained teeth for mating purposes, particularly as males have more pronounced teeth than females. Reef manta females are larger than males and can be identified by a simple cloaca located between their ventral fins, as well as the presence of mating scars on the pectoral fins. Males possess two claspers, which extend from their pelvic fins. Juvenile males have claspers that do not extend past their pelvic fins and which are minimally calcified. The only external way to distinguish an adult female from a juvenile is by the presence of mating scars on the pectoral fins. /=\

Manta Ray Behavior, Perception and Communication

Manta rays are generally solitary creatures who sometimes swim in small, loosely-organized schools of up to five individuals. Although the giant manta ray tends to be solitary, they aggregate at cleaning sites and to feed and mate. Although Reef manta rays are often found in groups when feeding, direct interactions between individuals seem to be limited to mating. Sometimes they swim together in formations that from the air resemble squadrons of stealth bombers.

Manta rays are diurnal (active mainly during the daytime), motile (move around as opposed to being stationary) and migratory (make seasonal movements between regions). They are most commonly seen feeding during the afternoon. They communicate with vision and chemicals usually detected by smelling and sense using vision, touch, sound, vibrations, electric signals and chemicals that can be detected by smelling. They emit an electric field using a well-developed electrosensory systems, which all rays and sharks possess.

Frank Pope wrote in The Times: Researchers say that mantas have a larger brain-to-body size ratio than any other fish and display signs of intelligence on a par with dolphins and whales, enabling them to socialise and co-operate while feeding. “I’ve seen cyclones of manta rays, with one hundred, two hundred individuals spinning together to create a vortex of water that concentrates the plankton in its centre,” said Guy Stevens, a manta biologist who works in the Maldives. [Source: Frank Pope, The Times, January 14, 2012]

With their eyes located on the sides of their head, manta rays can see in all directions. They communicate with each during courtship displays. It also has been suggested that olfaction may play a role during courtship. They are also able to detect sounds using their inner ears. [Source: Kourtney Simpkins, Animal Diversity Web (ADW)]

Manta Ray Swimming and Leaping

Unlike most other rays and skates, which tend to spend their time on the sea floor and undulate their bodies to get around, manta rays swim in the ocean like marine versions of flying dinosaurs. They use their large wing-like pectoral fins to slap and glide through the water much same way a bird flies through the sky. Like other rays, they use their broad pectoral fins rather than the tail for forward propulsion. This results in their graceful “flying” motion through the water.

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manta ray in Okinawa
Terence Monmaney wrote in Smithsonian magazine: Like many shark species, a manta ray must constantly move to avoid sinking and to keep oxygen-rich water flowing across its gills. And because it is a very large animal that depends on a very small, even microscopic food source — plankton — the fish has to eat virtually all the time. Swimming through a plankton cloud, it opens its massive mouth, deploys special fins to funnel the seawater in, and filters out the tiny morsels with its comb-like gill plates. [Source: Terence Monmaney, Smithsonian magazine, October 2022]

Mantas normally swims at a slow, easy-gong pace, beating their pectoral fins up and down about 10 times a minute, but are capable of accelerating quickly to avoid predators. When they feed on plankton sometimes they rise through the water in spiraling motion, with their mouth agape, then descend and repeat the motion.

Manta rays are well-known for their ability to leap high into the air, sometimes somersaulting in the air and hitting the ocean surface with a loud crash.. Some hypothesize that this activity serves to rid the rays of parasites, while others view the behavior as playful. Manta rays have been observed gliding near the surface with the upturned tips of their pectoral fins sticking up out of the water. [Source: Monica Weinheimer and R. Jamil Jonna, Animal Diversity Web (ADW) /=]

Manta Ray Migrations and Home Ranges

The giant manta ray is a migratory species and seasonal visitor along productive coastlines with regular upwelling, in oceanic island groups, and near offshore pinnacles and seamounts. The timing of these visits varies by region and seems to correspond with the movement of zooplankton, current circulation and tidal patterns, seasonal upwelling, seawater temperature, and possibly mating behavior.[Source: NOAA]

Frank Pope wrote in The Times: Tracking studies have revealed that they travel to the ocean depths, rather than remaining on the surface where their food is concentrated. Andrea Marshall, a manta biologist based in Mozambique, said: “Not only have we tracked them across thousands of kilometers of ocean, we’ve discovered that they are incredibly deep divers. we don’t know what they’re doing down there.” [Source: Frank Pope, The Times, January 14, 2012]

Manta in the Maldives
Giant manta rays also appear to exhibit a high degree of plasticity or variation in terms of their use of depths within their habitat. During feeding, giant manta rays may be found aggregating in shallow waters at depths less than 10 meters. However, tagging studies have also shown that the species conducts dives of up to 200 to 450 meters (660 to 1,475 feet) and is capable of diving to depths exceeding 1,000 meters (3,300 feet). This diving behavior may be influenced by season and shifts in prey location associated with the thermocline.

Reef manta rays displays site fidelity (preference for a particular area), likely associated with food availability, cleaning stations where parasites are removed by reef fishes, reproductive sites, and migratory, landmarks. According to Animal Diversity Web: Daily migration distances can be up to 70 kilometers (43 miles), and annual migrations from 270-500 kilometers (175 to 315 miles). Home range size varies due to mating habits or productivity of different areas. Migrations appear to be linked to changes in temperature and zooplankton productivity. When monsoons occur, the shift in ocean currents affects which direction reef manta rays go, by allowing them to either move with the currents or encounter less difficulty navigating against them. The overall trend is that they migrate south in the summer and return north during the winter. It is also thought that the coral reefs and islands act as landmarks for the manta rays to orient themselves in their home range as well as help them navigate during migration. [Source: Kourtney Simpkins, Animal Diversity Web (ADW) /=]

Feeding Manta Rays

Unlike most rays which have their mouths on the underside of their bodies, the manta ray has its mouth at the front of its body, allowing it to feed continuously as it moves through the sea. Mantas have tiny teeth which they don’t use when feeding. They strain planktonic organisms (and sometimes small schooling fishes) from the water.

Manta rays primarily feed on planktonic organisms such as euphausiids, copepods, mysids, decapod larvae, and shrimp, but some studies have noted their consumption of small and moderately sized fish as well. When feeding, mantas hold their cephalic fins in an “O” shape and open their mouths wide, creating a funnel that pushes water and prey through their mouth and over their gill rakers. Manta rays use many different types of feeding strategies, such as barrel rolling (doing somersaults over and over again) and creating feeding chains with other mantas to maximize prey intake.[Source: NOAA]

Manta feeding
Manta rays are attracted by masses of plankton. When feeding, manta rays open their mouths wide and use their "horns" (cephalic fins) to direct food and water into their mouths. The water leaves through the manta ray’s throat through slits on either side of its head. The slits are lined with combs that catch plankton. Manta ray gills are flared to allow large volumes of water to pass through their mouth and filtering system. Manta rays are often hang out on the edges of reef channels where the changing tide carry eggs, larval fish and tiny crustaceans out to the open sea. They often follow the tides and feed virtually non-stop.

The large cephalic fins on either side of the mouth can be extended to form a funnel that scoops planktonic organisms, small fishes and crustaceans into the ray’s mouth. Manta rays have a highly developed filter system on their gill arches that traps small animals taken in with water during respiration. When feeding, their cephalic horns are extended and their swimming becomes more deliberate. Plankton is filtered using the ventrally located gill slits. Reef manta rays follow the tidal changes that concentrate zooplankton in shallower atoll channels, increasing feeding rates. [Source: Monica Weinheimer and R. Jamil Jonna, Animal Diversity Web (ADW) /=]

Manta Rays Feasting Around a Small island in the Maldives

Bruce Barcott wrote in National Geographic, In the Maldives, “there is an uninhabited island named Hanifaru. It's not much to see from the air: a spray of tropical shrubs on what appears to be a truckload of sand. Hanifaru is so small a child could walk its entire scimitar-shaped coastline in a ten-minute stroll. The island's size isn't unusual for the Maldives, a collection of 1,192 tiny islands clumped in 26 atolls encompassed by the vastness of the Indian Ocean. But several times a year, when time and tide align, manta rays from throughout the Maldives converge here to feed in a spectacular coral-reef ballet.” [Source: Bruce Barcott, National Geographic, July 2009]

From May through November, when the lunar tide pushes against the Indian Ocean's southwestern monsoon current, a suction effect pulls tropical krill and other plankton from deep water up to the surface. The current sweeps the krill into the cul-de-sac of Hanifaru Bay. If the krill stayed at the surface, they'd wash over the bay's coral walls and out to the safety of the open sea. But they can't. Instinct forces them to dive away from daylight. When they do, they get trapped deep in the bowl. In just a few hours a massive concentration of plankton builds up, a swarm so thick it turns the water cloudy.

"Just after high tide you'll see a few manta rays turn up," says Guy Stevens, a British marine biologist who's been researching the Maldives mantas for the past three years. "Then poof, a whole group will move in, and you'll get as many as 200 feeding for two to four hours in a bay no bigger than a soccer field." These massive fish (the wingspans of Maldives mantas can reach 12 feet) are dynamic filter feeders, shoveling their shoe-box mouths through krill like threshers through wheat, inhaling prey. They barrel roll when they hit a rich patch, somersaulting backward to stay in the hot spot. They chain feed, following each other in a train of open maws.

In the tight confines of Hanifaru Bay, mantas must expand their repertoire, and Stevens has identified maneuvers rarely seen by scientists. When 50 or more fish chain feed in the bay, something extraordinary happens. The head of the line catches the tail, and the chain spins into a vortex. "We call that cyclone feeding," says Stevens. "When you get more than a hundred mantas doing that, they start to spiral out. When the chain breaks down, you get chaos feeding." The stately dance in the milky waters turns into a free-for-all, with hundreds of mantas bumping into each other. Adding to the confusion are whale sharks — languid, plankton-eating giants, each about the size of a 40-foot shipping container — that show up to share the spoils. Within hours the plankton run out, the feast winds down, and the mantas plow the bay's sandy bottom with their cephalic fins to throw hidden prey back into the water column.

Manta Ray Reproduction and Offspring

Manta rays are viviparous (they give birth to live young that developed in the body of the mother) and iteroparous (offspring are produced in groups such as litters). They engage in internal reproduction in which sperm from the male fertilizes the egg within the female. Manta rays engage in seasonal breeding. Reef manta ray females mate once every one to two years. The breeding season is typically October through January. The gestation period ranges from 4 to 13 months, with the average gestation period being 12 months. The number of offspring ranges from zero to two. [Source: Kourtney Simpkins, Animal Diversity Web (ADW) /=]

On average females reach sexual maturity at age eight years when they are four to five meters wide; males do so at six years when they are three meters wide. Females typically have a year-long resting period between pregnancies, with some individuals resting for up to two years. Because not all females participate in mating at a given time, females may display cues to show their receptiveness to males.

Male reef manta start to sexually mature at 9 to 13 years old, while females need 13 to 17 years to mature. A female gives birth to only one pup every 2 to 6 years after about one year of pregnancy. Reef manta rays give birth to live young. Although capable of bearing young annually, females tend to reproduce biannually, likely due to energy constraints. It is most common for them to bear one pup, though it is possible to bear two. Young are about 1.2 to 1.7 meters wide at birth.

Although females nourish the pups before birth, there is no parental care given by either parent after birth; in fact, there are records of adults, possibly parents, attacking young shortly after birth. During the gestation embryos are nourished in the mother's uterus not by a placenta but with a protein and lipid-rich histotrophe, secreted by uterine villi.Typically, only one pup develops at a time. It is very rare to find young individuals, and it has been hypothesized that juveniles may segregate themselves from the adult population until attaining adulthood, or that newborn/juvenile mortality is quite high.

Manta Ray Mating

Manta rays have among the lowest fecundity of all rays and sharks, typically giving birth to only one pup every two to three years. They are polygynandrous (promiscuous), with both males and females having multiple partners. During the mating season males chase females and swim underneath them so their undersides face each. If a pair decides to mate the male inserts his claspers.

According to Animal Diversity Web: Rays are reported to engage in prolonged mating that may last up to four hours. According to one observation of manta rays, mating occurred right at the surface of the water, with a graceful undulating motion of their bodies, and the male alternately inserting his claspers (paired male reproductive organs) into the female. The pair did not copulate continuously, but swam about for short periods. .[Source: Monica Weinheimer and R. Jamil Jonna, Animal Diversity Web (ADW) /=]

There are five basic steps in reef manta ray mating: chasing, biting, copulation, post-copulation holding, and separating. Courting can take up to two hours, with males exhibiting their willingness to mate by swimming faster or in unison with other males, performing complex swim patterns, or breaching the water. If a female does not want to mate with a specific male she will buck and knock him off when he tries to copulate. Once a male has positioned himself with a female, he bites down on her pectoral fin and turns upside down. Scarring on females' pectoral fins suggests that lateralization occurs between the rays, with males favoring females' left pectoral fins. Copulation usually lasts 15 to 35 seconds, with the rays continuing to move through the water together. Once copulation is complete there is no further contact between mating pairs. (Marshall and Bennett, 2010) /=\

Manta Ray Hitchhikers and Cleaning Stations

In a phenomena only discovered in 1988, normally-open-ocean manta rays were observed coming to special "cleaning stations," specific rocks or areas along channels off the island of Yap in Micronesia, where small fish called wrasses removed parasites from their bodies while the manta rays fluttered in place in the current. The grooming of algae and other marine growths by wrasses is believed to help manta rays fend off life-threatening infections.

Describing the wrasses at work, David Doubilet wrote in National Geographic, "Suddenly wrasses about three inches long dart from the coral below and head for the manta. The creature then opens its enormous mouth, and a wrasse enters the white cave, picking between the gill arches that support the gills.”

Other fish such as orange clarion angelfish have also been observed cleaning parasites and marine growth off of manta rays. Jacks have been seen nipping at loose manta skin and using the bodies of mantas as covers for raids on other fish. Manta rays are often accompanied by fusilier fish. Remora often attach themselves to the manta ray body.

When approached by a diver, manta rays sometimes turn over their back so their stomachs can be scratched. On occasion groups of mantas have been observed leaping clear out of the water. When they hit the water the make a resonating slapping sound that can sometimes be heard more than a mile away. Scientist speculate that the manta rays do this to try to dislodge parasites. They probably like be scratched for the same reason.

Image Sources: Wikimedia Commons, NOAA

Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated April 2023