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Manta birostrisAtlantic manta(Also: Blanketfish; Giant Manta; Sea devil)

By Gregory Shuraleff II

Geographic Range

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. (Bigelow and Schroeder, 1954; FishBase, 1999; OceanLink, 1997)

Habitat

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. (Acker (MRBH), 2001; Bigelow and Schroeder, 1954)

  • Range depth
    0 to 120 m
    0.00 to 393.70 ft

Physical Description

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. ("Manta Rays", 1989; Acker (MRBH), 2001; Bigelow and Schroeder, 1954)

  • Sexual Dimorphism
  • female larger
  • Range mass
    1200 to 1400 kg
    2643.17 to 3083.70 lb

Reproduction

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. (Acker (MRBH), 2001; Yano, et al., 1999)

  • Average age at sexual or reproductive maturity (female)
    Sex: female
    2190 days
    AnAge

Lifespan/Longevity

  • Average lifespan
    Status: captivity
    20 years
    AnAge

Behavior

Manta rays are solitary, free swimmers who are not territorial. Manta birostris use their flexible pectoral fins to swim gracefully through the ocean. Atlantic manta rays are most active during the mating season, and have been recorded leaping out of the water to heights of 7 feet, then smacking against the surface. By doing this, mantas may remove irritating parasites and dead skin on their large bodies. Also, Manta birostris have been seen at "cleaning stations" with wrasse fish swimming about them picking off parasites and dead skin. Another symbiotic interaction that mantas have is with remora fish, which attach to the giant mantas and hitch rides with them while feeding on the mantas parasites and on plankton. Manta rays have no particular anti-predator specializations other than their tough skin, but due to their size they do not have many natural predators. Large sharks have been known to attack manta rays. ("Manta Rays", 1989; Bigelow and Schroeder, 1954; Dive Asia, 2004)

Food Habits

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. ("Manta Rays", 1992; Dive Asia, 2004; Perlmutter, 1961)

  • Primary Diet
  • carnivore
    • eats non-insect arthropods

Economic Importance for Humans: Positive

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. ("Manta Rays", 1992; Colla (oceanlight) and Martin, 1998; McCormick, et al., 1963)

Economic Importance for Humans: Negative

Manta birostris have no adverse affects on humans.

Conservation Status

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.

Other Comments

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. (Bigelow and Schroeder, 1954; McCormick, et al., 1963)

Contributors

George Hammond (editor), Animal Diversity Web.

Gregory Shuraleff II (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

coastal

the nearshore aquatic habitats near a coast, or shoreline.

ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

filter-feeding

a method of feeding where small food particles are filtered from the surrounding water by various mechanisms. Used mainly by aquatic invertebrates, especially plankton, but also by baleen whales.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

internal fertilization

fertilization takes place within the female's body

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

migratory

makes seasonal movements between breeding and wintering grounds

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

pelagic

An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).

reef

structure produced by the calcium carbonate skeletons of coral polyps (Class Anthozoa). Coral reefs are found in warm, shallow oceans with low nutrient availability. They form the basis for rich communities of other invertebrates, plants, fish, and protists. The polyps live only on the reef surface. Because they depend on symbiotic photosynthetic algae, zooxanthellae, they cannot live where light does not penetrate.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

zooplankton

animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)

References

1992. Manta Rays. Pp. 1512-1514 in Encyclopedia of the Animal, vol. 8 (Ott-Rhe). New York: Boy Books.

1989. Manta Rays. Pp. 582-583 in Wildlife of the World Encyclopedia, vol. 10 (Rav-Slo). New York: Cavendish Publishing.

Acker (MRBH), B. 2001. "Manta facts" (On-line). Manta Ray Bay Hotel and Yap Divers. Accessed 11/01/04 at http://www.mantaray.com.

Bigelow, H., W. Schroeder. 1954. Fishes of the Western North Atlantic. Copenhagen: Yale University.

Colla (oceanlight), P., R. Martin. 1998. "Giant Pacific Manta Ray Photos/On the Biology of the Manta Ray" (On-line). Phillip Colla Photography. Accessed 11/01/04 at http://www.oceanlight.com/html/manta_birostris.html.

Dive Asia, 2004. "Dive Asia Reef Ecology Guide- Cartilaginous Fishes" (On-line). Dive Asia, Diving in Phuket, Thailand and Burma. Accessed 11/01/04 at http://www.diveasia.com/reef-guide/cartilaginous.htm.

FishBase, 1999. "Manta birostris" (On-line). FishBase.org. Accessed March 7, 2000 at http://www.fishbase.org/Seach.cfm.

McCormick, H., T. Allen, W. Young. 1963. Shadows of the Sea. Philadelphia: Chilton Company.

OceanLink, 1997. "Ocean Link Answers to Chondrichthyes Questions" (On-line). OceanLink. Accessed 11/01/04 at http://oceanlink.island.net/ask/chondrichthyes.html#anchor139401.

Perlmutter, A. 1961. Guide to Marine Fishes. New York: New York University Press.

Yano, K., F. Sato, T. Tomoko. 1999. Observations of mating behavior of the manta ray, Manta birostris, at the Ogasawara Islands, Japan. Ichthyological Research, 46: 289-296.

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