Average lifespan
Status: captivity: 20 years.
In the past, Manta birostris was commercially hunted from small boats. Currently this species is rarely hunted. The biggest impact that the manta ray currently has comes from tourism, with dive industries being created for tourists who want to swim along side these gentle giants. Inquisitive mantas will approach and even solicit attention from divers, apparently enjoying the stimulation provided by human contact and the bubbles from scuba exhaust. Although, it has been recorded that manta rays that frequently encounter humans will shy away from contact with humans.
Positive Impacts: ecotourism
Manta birostris have no adverse affects on humans.
Population sizes of Manta birostris are unknown. Because of their slow reproductive rate, they are very vulnerable to overfishing. However, there does not appear to be commercial harvesting at this time. The IUCN lists this species as "Data Deficient," meaning they don't have enough information to assess its conservation status.
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: no special status
The average life span of Manta birostris is 18-20 years. The Atlantic manta ray was once thought to be aggressive and harmful to humans as sailors created myths about them. The common myth was that mantas could capsize ones boat by leaping out of the water and crashing down upon it. Another common misconception is that mantas drown swimmers by wrapping around them. They are called "devil" ray because of the cephalic fins at the front of their heads, which resemble the horns of a devil. Also fishing boats reported that Atlantic manta rays would circle about their boats for long periods of time. These mantas were probably just displaying their corralling behavior during feeding.
In the past, two other species of manta, known as the "lesser" devil rays, Manta birostris (Pacific manta ray) and Manta alfredi (Prince Alfred's manta ray) were considered separate from Manta birostris. They have since been recognized as the same species, all now called M. birostris.
The name of manta is derived from the Spanish word, meaning blanket.
Manta rays are filter feeders and primarily planktivores. They often slowly swim in vertical loops. Some researchers suggest this is done to keep the rays prey within the area while feeding. Their large, gaping mouths and cephalic lobes unfurled are used to corral planktonic crustaceans and small schooling fish. Manta rays filter water through their gills and organisms in the water are trapped by a filtering device, which consists of plates in the back of the mouth that are made of pinkish-brown tissue that span between the support structures of the gills. The teeth of Manta birostris are nonfunctional during feeding.
Animal Foods: fish; aquatic crustaceans; zooplankton
Foraging Behavior: filter-feeding
Primary Diet: carnivore (Eats non-insect arthropods)
Manta rays are found in tropical and warm temperate coastal regions of the world's oceans, generally between 35 degrees north and south latitude, including the coasts of southern Africa, ranging from southern California to northern Peru, North Carolina to southern Brazil, and the Gulf of Mexico.
Biogeographic Regions: indian ocean (Native ); atlantic ocean (Native ); pacific ocean (Native )
Manta birostris, unlike most other rays, are found near the surface of the ocean and to depths of 120 meters. Atlantic manta rays stay closer to shore in the warmer waters where food sources are more abundant, but occasionally can be found further from shore.
Range depth: 0 to 120 m.
Habitat Regions: tropical ; saltwater or marine
Aquatic Biomes: pelagic ; reef ; coastal
Manta rays are easily reconized in the ocean by their large pectoral "wings." Manta birostris have no caudal fins and a small dorsal fin. They have two cephalic lobes that extend from the front of the head and a broad, rectangular, terminal mouth containing small teeth exclusively in the lower jaw. The gills are located on the underside of the body. Manta rays also have a short, whip-like tail that, unlike many rays, has no sharp barb. Atlantic manta ray pups weigh 11 kg at birth and their growth is rapid, with pups virtually doubling the body width from birth through the first year of life. Manta rays show little dimorphism between the sexes with wingspan in males ranging from 5.2 - 6.1 meters and females ranging from 5.5 - 6.8 meters. The largest ever recorded was 9.1 meters. One of the distinct features of manta rays, and of the class Chondrichthyes, is that the entire skeleton is made of cartilage, which allows for a wide range of motion. These rays vary in color from black to grayish blue along the back, and a white underside with grayish blotchs that have been used to identify individual rays. The skin of manta rays is rough and scaly, like that of most sharks.
Range mass: 1200 to 1400 kg.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: female larger
Manta birostris are sexually mature at 5 years of age. The mating season of sexually mature manta rays occurs from early December to late April. Mating takes place in tropical waters (26-29 degrees Celsius), and around rocky reef areas from 10-20 meters in depth. Manta rays gather in large numbers during this season, where several males will court a single female. The males swim closely behind the tail of the female at faster than usual speeds (9-12km/h). This courtship will last for about 20-30 minutes at which point the female decreases her swimming speed and a male will grasp one side of the female's pectoral fin by biting it. He arranges his body under that of the females. The male will then insert his clasper in the cloaca of the female and insert his sperm, this usually lasting around 90-120 seconds. The male will then swim away rapidly and the next male will repeat this same process. However, after the second male the female usually swims away leaving behind the other courting males. The gestation period of Manta birostris is 13 months, after which females give birth to 1 or 2 live young. Pups are born wrapped up by their pectoral fins, but soon after become free swimmers and fend for theirselves. Manta ray pups are between 1.1 and 1.4 meters when they are born.
Key Reproductive Features: iteroparous ; seasonal breeding ; sexual ; fertilization (Internal ); viviparous
Average age at sexual or reproductive maturity (female)
Sex: female: 2190 days.
The giant manta (Manta birostris) is part of the Mobulidae family, a small group of large rays that spread their wings while swimming. Manta birostris is also known as the devil ray (Allaby 2009). Its preferred habitat is tropical or subtropical waters. It is the most widely distributed manta, and has been found in three major oceans: The Pacific, Indian, and Atlantic (Kashiwagi et al. 2011).
Manta birostris has an average wingspan of 5.2 to 6.8 meters (Animal Diversity Web 2014) and an average weight of 1,350 kg (Manta Matcher 2015). It has the biggest brain mass per body mass ratio among fish in the world (Csilla et al. 2016). Each manta has dark upper sides, bright white shoulder patches, and a unique spot pattern on its under-side, centrally on the stomach (Marshall et al. 2009), making it possible to identify and trace each giant manta and study it in the wild (Town 2013). The genus Manta was thought to include one species until 2009, when Manta birostris and Manta alfredi were recognized as two separate species (Sawers and Stevens 2015).
Manta birostris live in groups and feed together on different types of plankton, small fish, and crustaceans. The Manta birostris´s lifespan is 40 years (Manta Ray of Hope 2016a). Manta birostris reaches its sexual maturity at 10-15 years of age. Its mode of reproduction is ovoviviparity. Females get pregnant once every 2-3 years, with a 12-month gestational period, and bear one live pup with each pregnancy and 10-16 pups in a lifetime (Marshall and Bennett 2010, Woodward 2009, Manta Trust 2016).
Manta birostris has only two predators in the sea, sharks and whales. The main cause for their population decline is habitat destruction, marine debris, and climate change (Manta Ray of Hope 2016a). Because of its high price on the Chinese market, where it is used as an ingredient for traditional medicinal tonics, Manta birostris has been overfished (Marshall et al. 2011). Manta meat is also highly valued; an average of 65-80 thousand kg is consumed annually (Manta Ray of Hope 2016c). A dead manta is valued at US $40–$500, depending on its size.
With environmental education and sustainable business alternatives (tourism and diving operators), local neighbors are now conservationists of this species (Peschak 2016). Dive tourism is estimated to produce US $4 million each year
In 2011, Manta birostris became part of the IUCN Red List for Endangered Species, tagged with vulnerable status. IUCN estimates sub-populations (total number of species found in different groups) of 100-1000 individuals (Marshall et al. 2011). In November of 2011, the Government of Ecuador’s proposals to the Convention on the Conservation of Migratory Species of Wild Animals (CMS) to add Manta birostris to Appendices I and II of the treaty was approved (Convention on International Trade in Endangered Species of Wild Fauna and Flora 2013). The giant manta is now protected and can no longer be commercialized or traded in 116 countries.
MantaMatcher represents the first global online database for manta rays, designed specifically to manage manta ray (manta alfredi and manta birostri) sightings and identifications across their distribution.
The giant oceanic manta ray, giant manta ray, or oceanic manta ray (Mobula birostris) is a species of ray in the family Mobulidae, and the largest type of ray in the world. It is circumglobal and is typically found in tropical and subtropical waters, but can also be found in temperate waters.[4] Until 2017, the species was classified in the genus Manta, along with the smaller reef manta ray (Mobula alfredi). DNA testing revealed that both species are more closely related to rays of the genus Mobula than previously thought. As a result, the giant manta was renamed as Mobula birostris to reflect the new classification.[5]
The giant oceanic manta ray can grow up to 9 m (30 ft) in maximum length[6] and to a disc size of 7 m (23 ft) across with a weight of about 3,000 kg (6,600 lb)[7][8] but average size commonly observed is 4.5 m (15 ft).[9] It is dorsoventrally flattened and has large, triangular pectoral fins on either side of the disc. At the front, it has a pair of cephalic fins which are forward extensions of the pectoral fins. These can be rolled up in a spiral for swimming or can be flared out to channel water into the large, forward-pointing, rectangular mouth when the animal is feeding. The teeth are in a band of 18 rows and are restricted to the central part of the lower jaw. The eyes and the spiracles are on the side of the head behind the cephalic fins, and the gill slits are on the ventral (under) surface. It has a small dorsal fin and the tail is long and whip-like. The manta ray does not have a spiny tail as do the closely related devil rays (Mobula spp.) but has a knob-like bulge at the base of its tail.[10]
The skin is smooth with a scattering of conical and ridge-shaped tubercles. The colouring of the dorsal (upper) surface is black, dark brown, or steely blue, sometimes with a few pale spots and usually with a pale edge. The ventral surface is white, sometimes with dark spots and blotches. The markings can often be used to recognise individual fish.[11] Mobula birostris is similar in appearance to Mobula alfredi and the two species may be confused as their distribution overlaps. However, there are distinguishing features.
The oceanic manta ray is larger than the reef manta ray, 4 to 5 metres in average against 3 to 3.5 metres.[12] However, if the observed rays are young, their size can easily bring confusion. Only the colour pattern remains an effective way to distinguish them. The reef manta ray has a dark dorsal side with usually two lighter areas on top of the head, looking like a nuanced gradient of its dark dominating back coloration and whitish to greyish, the longitudinal separation between these two lighter areas forms a kind of "Y". While for the oceanic manta ray, the dorsal surface is deep dark and the two white areas are well marked without gradient effect. The line of separation between these two white areas form meanwhile a "T".
Difference can also be made by their ventral coloration, the reef manta ray has a white belly with often spots between the branchial gill slits and other spots spread across trailing edge of pectoral fins and abdominal region. The oceanic manta ray has also a white ventral coloration with spots clustered around lower region of its abdomen. Its cephalic fins, inside of its mouth and its gill slits are often black.
The giant oceanic manta ray has a widespread distribution in tropical and temperate waters worldwide. In the Northern Hemisphere, it has been recorded as far north as southern California and New Jersey in the United States, Aomori Prefecture in Japan, the Sinai Peninsula in Egypt, and the Azores in the northern Atlantic. In the Southern Hemisphere, it occurs as far south as Peru, Uruguay, South Africa, and New Zealand.[13]
It is an ocean-going species and spends most of its life far from land, travelling with the currents and migrating to areas where upwellings of nutrient-rich water increase the availability of zooplankton.[14] The oceanic manta ray is often found in association with offshore oceanic islands.[10]
There are few public aquariums with giant manta ray in captivity. Since 2009, captive manta rays have been classified as Ꮇ. alfredi and there have been no facilities to display Ꮇ. birostris for some time.
Since late 2018 it has been exhibited at Nausicaä Centre National de la Mer in France and Okinawa Churaumi Aquarium in Japan.[15][16] There are also reports that they were kept at the Marine Life Park, part of the Resorts World Sentosa in Singapore.[17][18]
When traveling in deep water, the giant oceanic manta ray swims steadily in a straight line, while further inshore it usually basks or swims idly around. Mantas may travel alone or in groups of up to 50 and sometimes associate with other fish species, as well as sea birds and marine mammals. About 27% of their diet is based on filter feeding,[19] and they will migrate to coastlines to hunt varying types of zooplankton such as copepods, mysids, shrimp, euphausiids, decapod larvae, and on occasion, varying sizes of fish.[20] When foraging, it usually swims slowly around its prey, herding the planktonic creatures into a tight group before speeding through the bunched-up organisms with its mouth open wide.[19] While feeding, the cephalic fins are spread to channel the prey into its mouth and the small particles are sifted from the water by the tissue between the gill arches. As many as 50 individual fish may gather at a single, plankton-rich feeding site.[11] Research published in 2016 proved about 73% of their diet is mesopelagic (deep water) sources including fish. Earlier assumptions about exclusively filter feeding were based on surface observations.[21]
The giant oceanic manta ray sometimes visits a cleaning station on a coral reef, where it adopts a near-stationary position for several minutes while cleaner fish consume bits of loose skin and external parasites. Such visits occur most frequently at high tide.[22] It does not rest on the seabed as do many flat fish, as it needs to swim continuously to channel water over its gills for respiration.[23]
Males become sexually mature when their disc width is about 4 m (13 ft), while females need to be about 5 m (16 ft) wide to breed. When a female is becoming receptive, one or several males may swim along behind her in a "train". During copulation, one of the males grips the female's pectoral fin with his teeth and they continue to swim with their ventral surfaces in contact. He inserts his claspers into her cloaca and these form a tube through which the sperm is pumped. The pair remains coupled together for several minutes before going their own way.[24]
The fertilized eggs develop within the female's oviduct. At first, they are enclosed in an egg case and the developing embryos feed on the yolk. After the egg hatches, the pup remains in the oviduct and receives nourishment from a milky secretion.[25] As it does not have a placental connection with its mother, the pup relies on buccal pumping to obtain oxygen.[26] The brood size is usually one but occasionally two embryos develop simultaneously. The gestation period is thought to be 12–13 months. When fully developed, the pup is 1.4 m (4 ft 7 in) in disc width, weighs 9 kg (20 lb) and resembles an adult. It is expelled from the oviduct, usually near the coast, and it remains in a shallow-water environment for a few years while it grows.[11][25] Females only reproduce every two to three years. Long gestation periods and slow reproduction rates make this species highly vulnerable to shifts in population.
The oceanic manta has one of the largest brains, weighing up to 200 g (five to ten times larger than a whale shark brain), and the largest brain-to-mass ratio of any fish. It heats the blood going to its brain and is one of the few animals (land or sea) that might pass the mirror test, seemingly exhibiting self-awareness.[27]
Because of its large size and velocity in case of danger (24 km/h escape speed),[28] the oceanic manta ray has very few natural predators that could be fatal to it. Only large sharks and dolphins, such as the tiger shark (Galeocerdo cuvier), the great hammerhead shark (Sphyrna mokarran), the bullshark (Carcharhinus leucas), the false killer whale (Pseudorca crassidens), and the killer whale (Orcinus orca), are capable of preying on the ray. Nonlethal shark bites are very common occurrences, with a vast majority of adult individuals bearing the scars of at least one attack.[29]
The oceanic manta ray is considered to be endangered by the IUCN’s Red List of Endangered Species because its population has decreased drastically over the last twenty years due to overfishing.[30] Because M. birostris feeds in shallow waters, there is a higher risk of them getting caught in fishing equipment, especially in surface drift gillnets and bottom set nets.[31] Whatever the type of fishing (artisanal, targeted or bycatch), the impact on a population which has a low fecundity rate, a long gestation period with mainly a single pup at a time, and a late sexual maturity can only be seriously detrimental to a species that cannot compensate for the losses over several decades.[30]
Since the 1970s,[32] fishing for manta rays has been significantly boosted by the price of their gill rakers on the traditional Chinese medicine market.[33] In Chinese culture, they are the main ingredient in a tonic that is marketed to increase immune system function and blood circulation, though there is no strong evidence that the tonic is actually beneficial to health. For this reason and others, gill rakers are sold at relatively high prices – up to $400 per kilogram – and are sold under the trade name pengyusai.[34][32] In June 2018 the New Zealand Department of Conservation classified the giant oceanic manta ray as "Data Deficient" with the qualifier "Threatened Overseas" under the New Zealand Threat Classification System.[35]
There is also the threat of microplastics in the diets of oceanic manta rays. A 2019 study in Indonesia's Coral Triangle was performed to determine if the filter-feeding megafauna of the area were accidentally ingesting microplastics, which can be eaten by filter-feeders either directly (by ingesting layers of plastic polymers that float on the surface of the water in feeding areas) or indirectly (by eating plankton that previously ate microplastics). The results of the study provided ample evidence that filter feeders, such as oceanic manta rays, that lived in the area were regularly consuming microplastics. Though it was also proven via stool samples that some of the plastic simply passed through the digestive systems of manta rays, the discovery is a concern because microplastics create sinks for persistent organic pollutants like dichloro-diphenyl-trichloroethanes (DDTs) and polycyclic aromatic hydrocarbons (PAHs). Manta rays that consume microplastics harboring these pollutants can suffer from a variety of health effects that range from short-term negative effects such as the reduction of bacteria in their guts, or long-term effects including pollutant-induced weakening of the population's reproductive fitness over future generations, which could negatively affect population levels of the rays in the future.[36]
M. birostris are also victims of bioaccumulation in certain regions. There has been at least one study that has shown how heavy metals such as arsenic, cadmium, and mercury can be introduced to the marine environment via pollution and can travel up the trophic chain. For example, there was a study in Ghana that involved the testing of tissue samples from six M. birostris carcasses; all of them showed evidence of high concentrations of arsenic and mercury (about 0.155–2.321 μg/g and 0.001–0.006 μg/g respectively). While the sample size was not the most ideal, it is a first step towards further understanding the true amount of bioaccumulation that M. birostris undergoes due to human pollution. These high levels of metals can cause harm to the people who consume M. birostris, and could also cause health problems for the M. birostris species itself. More studies need to be done in order to further confirm the negative health effects of bioaccumulation on M. birostris.[37]
Climate change combined with rising temperatures, are projected to cause a 10% decrease in the global population of phytoplankton with a potential 50% decrease in tropical areas. With these reductions could come a decrease in M. birostris populations.[38]
The giant oceanic manta ray, giant manta ray, or oceanic manta ray (Mobula birostris) is a species of ray in the family Mobulidae, and the largest type of ray in the world. It is circumglobal and is typically found in tropical and subtropical waters, but can also be found in temperate waters. Until 2017, the species was classified in the genus Manta, along with the smaller reef manta ray (Mobula alfredi). DNA testing revealed that both species are more closely related to rays of the genus Mobula than previously thought. As a result, the giant manta was renamed as Mobula birostris to reflect the new classification.