More Information

Additional Information

Pteromylaeus bovinusbullray(Also: Duckbill ray)

By Dylan Barrera; Caleb Dickerson; Bleu Grano; John Lambert

Geographic Range

The distribution of bull rays is not well-defined, but most observations report its range within tropical and subtropical waters of the Eastern Atlantic Ocean, between 44°N - 35°S, 19°W - 36°E, off the coast of Portugal down to the Saldanha Bay, South Africa. Bull rays have also been sighted in the Mediterranean Sea, the Black Sea, off the Canary Islands and Madeira, and in the Indian Ocean, off the coast of Kenya. (Schwartz, 2011)

Habitat

Bull rays are predominantly found in brackish coastal waters and prefer warm waters from the surf zone, which varies from one location to the next, to depths up to 150 m deep. They are commonly found in estuaries and lagoons, due to the abundance of prey in these habitats. (Dulcic, et al., 2008; Schwartz, 2011)

  • Range depth
    surf zone to 150 m
    to 492.13 ft

Physical Description

  • Sexual Dimorphism
  • female larger
  • sexes shaped differently
  • Range mass
    5.3 to 116 kg
    11.67 to 255.51 lb
  • Range length
    0.74 to 1.48 m
    2.43 to 4.86 ft

Development

Sexual development in bull rays begins when individuals reach approximately 100 cm in length. Disc-width at birth ranges from 250 mm to 270 mm. Total length at birth ranges from 530 mm to 560 mm, and weight ranges from 310 g to 345 g. Male and female development is divided into three stages: juvenile (I), subadult (II) and adult (III). For males, growth stage is noted by the shape and size of their tubercles. In Stage I, the anterior edge of the orbital area (the area above the eye) is smooth. In Stage II, tubercles form in the orbital area and slightly protrude above the eye. In Stage III, the tubercles are prominent and fully developed, with a cone-like shape. Juvenile and subadult males, stage I and II, respectively, have short, uncalcified and flexible claspers along with undeveloped, thread-like testes and genital ducts. During stage II, clasper grows quickly. As adults (stage III), claspers are elongated, calcified, and rigid. Adult males have fully developed and fully functional claspers, testes, and genital ducts. Female sexual development is marked by changes in appearance of their internal reproductive organs. During stage I, ovaries are white with microscopic oocytes and indistinct nidamental glands. During stage II, oocytes are translucent and the genital ducts are thread-like. During Stage III, the genital duct is fully developed. (Dulcic, et al., 2008; Seck, et al., 2002; Van Der Elst, 1993)

Embryonic development in bull rays occurs through a reproductive process known as ovoviviparity. Eggs are fertilized internally, and embryos develop in egg cases while receiving nourishment from yolk sacs until they hatch out from the thin-walled membranes and continue development in the uterus. While in the uterus, embryos absorb nourishment through a combination of enriched nutrients supplied by mucus, fat, and protein from the uterine lining. This nutritional secretion is termed histotroph or “uterine milk,” and is ingested through a developing pup's mouth and spiracles. This type of nutrient supply facilitates the birth of large offspring. Gestation lasts about six months, with 3 to 7 pups produced in each litter. (Demski and Wourms, 1993; Michael, 1993)

Reproduction

Like most elasmobranchs, bull rays are polygynandrous and mate with different partners throughout breeding season. While little documentation exists on the mating behaviors of elasmobranchs in general, a few species of rays and skates have been observed copulating in the wild. Pre-copulatory behavior occurs in many species of rays, and is illustrated by the scars and wounds left on the dorsal surface of females. In male eagle rays, precopulatory behaviors include diving upon and biting the backs of females during courtship. The male inserts a pair of modified anal fins called claspers into the female to begin coitus. Copulation may last up to several hours. It is believed that female receptivity is dependent on hormonal status. (Demski and Wourms, 1993)

Rays in the family Myliobatidae, which includes bull rays, reproduce on a yearly cycle that ranges begins in spring and ends in fall. Gestation in bull rays lasts approximately 6 months and results in 3 to 7 pups per litter. Most individuals become sexually mature by 4 to 6 years after birth. (Demski and Wourms, 1993; Michael, 1993; Militante, 2010)

  • Breeding season
    Mating season begins in spring and ends in fall.
  • Range number of offspring
    3 to 7
  • Average gestation period
    6 months
  • Average time to independence
    0 minutes
  • Range age at sexual or reproductive maturity (female)
    4 to 6 years
  • Range age at sexual or reproductive maturity (male)
    4 to 6 years

Females carry developing pups and nourish them with histotroph until they are born. There is no documentation of post-birth parental care in the family Myliobatidae. Bull ray pups are born fully developed and independent, able to fend for themselves. (Michael, 1993)

  • Parental Investment
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

There is little information available regarding the average lifespan of bull rays. Commonly, rays grow and mature slowly, and bull rays have been known to live up to 14 years in the wild. (Last and Stevens, 2009; Lipej, et al., 2009; Moyle and Cech, 2000)

  • Range lifespan
    Status: wild
    14 (high) years

Behavior

While there is little information the general behavior of bull rays, other members of the family Myliobatidae tend to be active swimmers, generally swimming in open water, near reefs, or near the surface. Myliobatid rays may exhibit social behavior, and have been observed swimming in pairs and in schools of a hundred or more. Members of this family have also been known to leap high out of water, an activity that some researchers believe may help rid them of parasites. Like other Mylobatidae, bull rays swim by undulating or flapping their enlarged wing-like pectoral fins to propel themselves forward through the water, resulting in a characteristic “flying” motion. Bull rays use their snout to plow through the sand while searching for prey. (Jonna and Wienheimer, 2002)

Home Range

Although no information is available regarding the average home range size of bull rays, members of their parent family, Mylobatidae, are not known to maintain home ranges.

Communication and Perception

Like most members of Chondrichthyes, bull rays have a lateral line, which they use to perceive their immediate environment. They also have nares for olfactory perception and eyes. Like other elasmobranchs, bull rays possess small electrical sensing organs, known as ampullae of Lorenzini, which form a subcutaneous electrosensory detection system. Located on the underside of the snout, the ampullae of Lorenzini detect weak electrical currents generated by the muscular contractions of their prey. Using this organ system, bull rays can detect prey buried several centimeters below the seafloor. (Jonna and Wienheimer, 2002; Moyle and Cech, 2000)

Food Habits

Bull rays are carnivores that feed on benthic invertebrates. Important food items include brachyuran crabs, hermit crabs, prawns, and other bottom-dwelling crustaceans. They also feed on gastropod molluscs, bivalves, and small squids. A predominant prey item for the bull ray in South Africa is the sand-burrowing surf clam. (Dulcic, et al., 2008; Schwartz, 2011)

  • Animal Foods
  • mollusks
  • aquatic crustaceans
  • other marine invertebrates

Predation

Humans are a significant predator of bull rays. In addition, they are often caught in trawl nets as bycatch by shrimp fishermen, and in shark exclusion nets deployed at coastal beaches along South Africa. Natural predators include great hammerhead sharks and various pinniped species, such as South African fur seals. ("Pteromylaeus bovinus", 2010; Weinheimer, 2011)

Ecosystem Roles

Bull rays are shallow water predators in soft-bottomed environments of the neritic zone. They forage and feed upon benthic fish and small invertebrates, and in doing so, are important secondary and tertiary consumers within their environment. Rays excavate the soft bottoms of the sea floor while foraging for invertebrate prey. Disturbed sediments are rapidly recolonized by macrofauna and their larvae. Thus, foraging and predatory activities create habitat diversity and environmental heterogeneity. (Thrush, et al., 1991; Zogaris and Dussling, 2010)

Bull rays are host to numerous endoparasites, including trematode flatworms, monogenean flatworm, and ascarid worm. (Vassiliades, 1982)

  • Ecosystem Impact
  • creates habitat
Commensal/Parasitic Species
  • Trematode flatworm (Probolitrema richiardii)
  • Monogenean flatworm (Monocotyle sp.)
  • Ascarid worm (Porrocaecum pastinacae)

Economic Importance for Humans: Positive

Although they are occasionally pursued by humans, bull rays are very rare and not commonly caught by fisherman. Otherwise, there are no known positive effects of bull rays on humans. (Seck, et al., 2002)

Economic Importance for Humans: Negative

Bull rays have sharp barbs on their tails, which can be troublesome for humans. Bull rays may rest on sandy bottoms within the intertidal zone, where humans may accidentally encounter them. Otherwise, there are no known adverse effects of bull rays on humans. (Schwartz, 2011)

  • Negative Impacts
  • injures humans
    • bites or stings

Conservation Status

Bull ray population size and trends are unknown, making it difficult to determine the potential conservation needs of this species. Bull rays are classified as “data deficient” on the IUCN's Red List of Threatened Species, indicating there is insufficient data to adequately evaluate its conservation status.

Contributors

Dylan Barrera (author), San Diego Mesa College, Caleb Dickerson (author), San Diego Mesa College, Bleu Grano (author), San Diego Mesa College, John Lambert (author), San Diego Mesa College, Paul Detwiler (editor), San Diego Mesa College, John Berini (editor), Animal Diversity Web Staff.

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

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

benthic

Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.

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.

brackish water

areas with salty water, usually in coastal marshes and estuaries.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

ectothermic

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

electric

uses electric signals to communicate

estuarine

an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

fertilization

union of egg and spermatozoan

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

intertidal or littoral

the area of shoreline influenced mainly by the tides, between the highest and lowest reaches of the tide. An aquatic habitat.

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).

molluscivore

eats mollusks, members of Phylum Mollusca

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.

oceanic islands

islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.

ovoviviparous

reproduction in which eggs develop within the maternal body without additional nourishment from the parent and hatch within the parent or immediately after laying.

pelagic

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

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

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

sedentary

remains in the same area

sexual

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

social

associates with others of its species; forms social groups.

solitary

lives alone

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

tropical

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

visual

uses sight to communicate

References

International Union for Conservation of Nature and Natural Resources. 2010. "Pteromylaeus bovinus" (On-line). Accessed April 14, 2011 at http://www.iucnredlist.org/apps/redlist/details/60127/0.

Demski, L., J. Wourms. 1993. The Reproduction and Development of Sharks, Skates, Rays, and Ratfishes: Introduction, History, Overview, and Future Prospects. Dordrecht, The Netherlands: Kluwer Academic Publishers.

Dulcic, J., L. Lovrenc, M. Bonaca, R. Jenko, B. Grbec, O. Guélorget, C. Capapé. 2008. The Bull ray in the Adriatic Sea. Cybium, 32/2: 119-123.

Jonna, R., M. Wienheimer. 2002. "Myliobatidae" (On-line). Encyclopedia of Life. Accessed May 04, 2011 at http://www.eol.org/pages/8882?expertise=middle.

Last, P., J. Stevens. 2009. Sharks and Rays of Australia. Collingwood, Australia: CSIRO.

Lipej, L., B. Mavric, J. Dulcic. 2009. Size of the Bull ray, Pteromylaeus bovinus (Geoffroy Saint-Hilaire, 1817), from the northern Adriatic. Journal of Applied Ichthyology, 25/Supplement 1: 103-105.

Michael, S. 1993. Reef Sharks and Rays of the World: A Guide to their Identification, Behavior, and Ecology. Annapolis, MD: Lighthouse Press.

Militante, C. 2010. "Pteromylaeus bovinus" (On-line). FishBase. Accessed March 18, 2011 at http://www.fishbase.org/Summary/SpeciesSummary.php?ID=5011&AT=bull+ray.

Moyle, P., J. Cech. 2000. Fishes: An Introduction to Ichthyology. Upper Saddle River, NJ: Prentice-Hall.

Schwartz, J. 2011. Tail spine characteristics of stingrays (Order Myliobatiformes) found in the northeast Atlantic, Mediterranean, and Black seas. Electronic Journal of Ichthyology, 1/1: 1-9.

Seck, A., Y. Diatta, A. Gueye-Ndiaye, C. Capapé. 2002. Observations on the reproductive biology of the Bull ray, Pteromylaeus bovinus (E. Geoffrey Saint-Hilare, 1879) (Chondrichthyes: Myliobatidae) from the coast of Senegal (eastern tropical Atlantic). Acta Adriatica, 43/1: 87-96.

Thrush, F., R. Pridmore, J. Hewitt, V. Cummings. 1991. Impact of ray feeding disturbances on sandflat macrobenthos: Do communities dominated by polychaetes or shellfish respond differently?. Marine Ecology Progress Series, 69: 245-252. Accessed May 15, 2010 at http://www.int-res.com/articles/meps/69/m069p245.pdf.

Van Der Elst, R. 1993. A Guide to the Common Sea Fishes of Southern Africa. Cape Town: Struik.

Vassiliades, G. 1982. Helminthes parasites des Poissons de mer des cotes du Senegal. Bulletin de P.I.F.A.N., 44: 78-99. Accessed May 15, 2010 at http://www.sist.sn/gsdl/collect/publi/index/assoc/HASHafde/6284353f.dir/doc.pdf.

Weinheimer, M. 2011. "Animal Diversity Web" (On-line). Myliobatidae. Accessed January 02, 2011 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Myliobatidae.html.

Zogaris, S., U. Dussling. 2010. On the occurrence of the Bull ray Pteromylaeus bovinus (Chondrichthyes: Myliobatidae) in the Amvrakikos Gulf, Greece. Mediterranean Marine Science, 11/1: 177-184.

Search

Navigation Links

Information
Classification

Classification