The
bull shark,
Carcharhinus leucas, also known as
Zambezi shark or unofficially known as
Zambi in Africa and
Nicaragua shark in
NicaraguaNicaragua is the largest country in the Central American American isthmus, bordered by Honduras to the north and Costa Rica to the south. The country is situated between 11 and 14 degrees north of the Equator in the Northern Hemisphere, which places it entirely within the tropics. The Pacific Ocean...
, is a
sharkSharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....
common worldwide in warm, shallow waters along coasts and in rivers. The bull shark is well known for its unpredictable, often aggressive behavior.
The Bull shark can thrive in both saltwater and freshwater and can travel far up
riverA river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
s. They have even been known to travel as far up as
IndianaIndiana is a US state, admitted to the United States as the 19th on December 11, 1816. It is located in the Midwestern United States and Great Lakes Region. With 6,483,802 residents, the state is ranked 15th in population and 16th in population density. Indiana is ranked 38th in land area and is...
in the
Ohio RiverThe Ohio River is the largest tributary, by volume, of the Mississippi River. At the confluence, the Ohio is even bigger than the Mississippi and, thus, is hydrologically the main stream of the whole river system, including the Allegheny River further upstream...
and
IllinoisIllinois is the fifth-most populous state of the United States of America, and is often noted for being a microcosm of the entire country. With Chicago in the northeast, small industrial cities and great agricultural productivity in central and northern Illinois, and natural resources like coal,...
in the
Mississippi RiverThe Mississippi River is the largest river system in North America. Flowing entirely in the United States, this river rises in western Minnesota and meanders slowly southwards for to the Mississippi River Delta at the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains...
, although there have been few recorded attacks. They are probably responsible for the majority of near-
shoreA shore or shoreline is the fringe of land at the edge of a large body of water, such as an ocean, sea, or lake. In Physical Oceanography a shore is the wider fringe that is geologically modified by the action of the body of water past and present, while the beach is at the edge of the shore,...
shark attackA shark attack is an attack on a human by a shark. Every year around 60 shark attacks are reported worldwide, although death is quite unusual. Despite the relative rarity of shark attacks, the fear of sharks is a common phenomenon, having been fueled by the occasional instances of serial attacks,...
s, including many attacks attributed to other
speciesIn biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
. However, bull sharks are not true freshwater sharks (unlike the
river sharkThe river sharks are five rare species of shark in the genus Glyphis, although, due to their secretive habits, other species could easily remain undiscovered. Their precise geographic range is uncertain, but the known species are documented in parts of South and Southeast Asia and Australia...
s of the genus
Glyphis).
Etymology
The name bull shark comes from the shark's stocky shapes, broad, flat snout and aggressive, unpredictable behavior. In
IndiaIndia , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
, the bull shark may be confused with the Sundarbans or
Ganges sharkThe Ganges shark is a rare species of requiem shark found in the Ganges River of India. It should not be confused with the Bull shark, which also inhabits the Ganges River and is sometimes incorrectly referred to as the Ganges shark....
. In
AfricaAfrica is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
it is also commonly called the
Zambezi RiverThe Zambezi is the fourth-longest river in Africa, and the largest flowing into the Indian Ocean from Africa. The area of its basin is , slightly less than half that of the Nile...
shark or just Zambi. Its wide range and diverse habitats result in many other local names, including Ganges River Shark, Fitzroy Creek Whaler, van Rooyen’s Shark, Lake Nicaragua Shark, river shark, freshwater whaler, estuary whaler, Swan River Whaler, cub shark, and shovelnose shark.
Distribution and habitat
The bull shark lives all over the world in many different areas and travels long distances. It is common in coastal areas of warm oceans, in rivers and
lakeA lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...
s, and occasionally salt and freshwater streams if they are deep enough. It is found to a depth of 150 metres (492.1 ft) but does not usually swim deeper than 30 metres (98.4 ft). In the Atlantic it is found from
MassachusettsThe Commonwealth of Massachusetts is a state in the New England region of the northeastern United States of America. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. As of the 2010...
to southern
BrazilBrazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
, and from
MoroccoMorocco , officially the Kingdom of Morocco , is a country located in North Africa. It has a population of more than 32 million and an area of 710,850 km², and also primarily administers the disputed region of the Western Sahara...
to
AngolaAngola, officially the Republic of Angola , is a country in south-central Africa bordered by Namibia on the south, the Democratic Republic of the Congo on the north, and Zambia on the east; its west coast is on the Atlantic Ocean with Luanda as its capital city...
. In the
Indian OceanThe Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
it is found from
South AfricaThe Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
to
KenyaKenya , officially known as the Republic of Kenya, is a country in East Africa that lies on the equator, with the Indian Ocean to its south-east...
,
IndiaIndia , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
, and
VietnamVietnam – sometimes spelled Viet Nam , officially the Socialist Republic of Vietnam – is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea –...
to
AustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
.
There are more than 500 bull sharks in the
Brisbane RiverThe Brisbane River is the longest river in south east Queensland, Australia, and flows through the city of Brisbane, before emptying into Moreton Bay. John Oxley was the first European to explore the river who named it after the Governor of New South Wales, Thomas Brisbane in 1823...
. One was reportedly seen swimming the flooded streets of
BrisbaneBrisbane is the capital and most populous city in the Australian state of Queensland and the third most populous city in Australia. Brisbane's metropolitan area has a population of over 2 million, and the South East Queensland urban conurbation, centred around Brisbane, encompasses a population of...
, Queensland, Australia, during the Queensland floods of late 2010/early 2011. Several were sighted in one of the main streets of Goodna, Queensland, Australia, shortly after the peak of the January, 2011, floods. There are greater numbers still in the canals of the
Gold CoastGold Coast is a coastal city of Australia located in South East Queensland, 94km south of the state capital Brisbane. With a population approximately 540,000 in 2010, it is the second most populous city in the state, the sixth most populous city in the country, and also the most populous...
, also in Queensland, Australia. A large bull shark was caught in the canals of
ScarboroughScarborough is a residential suburb of the Moreton Bay Region at the northernmost of the Redcliffe peninsula, approximately north-northeast of Brisbane, the state capital of Queensland, Australia...
, 2 hours north of the Gold Coast. In the
Pacific OceanThe Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
, it can be found from
Baja CaliforniaBaja California officially Estado Libre y Soberano de Baja California is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is both the northernmost and westernmost state of Mexico. Before becoming a state in 1953, the area was known as the North...
, to
EcuadorEcuador , officially the Republic of Ecuador is a representative democratic republic in South America, bordered by Colombia on the north, Peru on the east and south, and by the Pacific Ocean to the west. It is one of only two countries in South America, along with Chile, that do not have a border...
.
The shark has traveled 4000 kilometres (2,485.5 mi) up the
Amazon RiverThe Amazon of South America is the second longest river in the world and by far the largest by waterflow with an average discharge greater than the next seven largest rivers combined...
to
IquitosIquitos is the largest city in the Peruvian rainforest, with a population of 370,962. It is the capital of Loreto Region and Maynas Province.Located on the Amazon River, it is only above sea level, although it is more than from the mouth of the Amazon at Belém on the Atlantic Ocean...
in
PeruPeru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....
. It also lives in fresh water
Lake NicaraguaLake Nicaragua or Cocibolca or Granada or is a vast freshwater lake in Nicaragua of tectonic origin. With an area of , it is the largest lake in Central America, the 19th largest lake in the world and the 9th largest in the Americas. It is slightly smaller than Lake Titicaca. With an elevation...
, in the Ganges and Brahmaputra rivers of
West BengalWest Bengal is a state in the eastern region of India and is the nation's fourth-most populous. It is also the seventh-most populous sub-national entity in the world, with over 91 million inhabitants. A major agricultural producer, West Bengal is the sixth-largest contributor to India's GDP...
and
AssamAssam , also, rarely, Assam Valley and formerly the Assam Province , is a northeastern state of India and is one of the most culturally and geographically distinct regions of the country...
in eastern
IndiaIndia , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
and adjoining
BangladeshBangladesh , officially the People's Republic of Bangladesh is a sovereign state located in South Asia. It is bordered by India on all sides except for a small border with Burma to the far southeast and by the Bay of Bengal to the south...
. It can live in water with a high salt content as in St. Lucia Estuary in
South AfricaThe Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
.
After
Hurricane KatrinaHurricane Katrina of the 2005 Atlantic hurricane season was a powerful Atlantic hurricane. It is the costliest natural disaster, as well as one of the five deadliest hurricanes, in the history of the United States. Among recorded Atlantic hurricanes, it was the sixth strongest overall...
, many bull sharks were sighted in Lake Ponchartrain. Bull sharks have occasionally gone up the
Mississippi RiverThe Mississippi River is the largest river system in North America. Flowing entirely in the United States, this river rises in western Minnesota and meanders slowly southwards for to the Mississippi River Delta at the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains...
as far upstream as
Alton, IllinoisAlton is a city on the Mississippi River in Madison County, Illinois, United States, about north of St. Louis, Missouri. The population was 27,865 at the 2010 census. It is a part of the Metro-East region of the Greater St. Louis metropolitan area in Southern Illinois...
. They have also been found in the
Potomac RiverThe Potomac River flows into the Chesapeake Bay, located along the mid-Atlantic coast of the United States. The river is approximately long, with a drainage area of about 14,700 square miles...
in Maryland.
Freshwater tolerance
The bull shark is the best known of 43 species of elasmobranch in ten genera and four families to have been reported in fresh water. Other species that enter rivers include the stingrays (Dasyatidae,
PotamotrygonidaeRiver stingrays are Neotropical freshwater fishes of the Potamotrygonidae family .They are native to northern, central and eastern South America, living in rivers that drain into the Caribbean, and into the Atlantic as far south as the Río de la Plata in Argentina...
and others) and
sawfishSawfish, also known as the Carpenter Shark, are a family of rays, characterized by a long, toothy nose extension snout. Several species can grow to approximately . The family as a whole is largely unknown and little studied...
(Pristidae). Some
skateSkates are cartilaginous fish belonging to the family Rajidae in the superorder Batoidea of rays. There are more than 200 described species in 27 genera. There are two subfamilies, Rajinae and Arhynchobatinae ....
s (Rajidae),
smooth dogfishThe dusky smooth-hound or smooth dogfish, Mustelus canis, is a species of hound shark, family Triakidae. This shark is an olive grey or brown, and may have shades of yellow or grayish white. Females live to 16 years and males have a life span of 10 years...
es (Triakidae), and
sandbar sharkThe sandbar shark, Carcharhinus plumbeus, is a species of requiem shark, family Carcharhinidae, native to the Atlantic Ocean and the Indo-Pacific. It is distinguishable by its very high first dorsal fin and inter-dorsal ridge....
s (
Carcharhinus plumbeus) regularly enter estuaries. Elasmobranchs' ability to enter fresh water is limited because their blood is normally at least as salty (in terms of osmotic strength) as seawater through the accumulation of
ureaUrea or carbamide is an organic compound with the chemical formula CO2. The molecule has two —NH2 groups joined by a carbonyl functional group....
and trimethylamine oxide, but bull sharks living in fresh water reduce the concentration of these solutes by up to 50%. As a result, bull sharks living in fresh water need to produce twenty times as much urine as those in salt water.
Initially, scientists thought the sharks in
Lake NicaraguaLake Nicaragua or Cocibolca or Granada or is a vast freshwater lake in Nicaragua of tectonic origin. With an area of , it is the largest lake in Central America, the 19th largest lake in the world and the 9th largest in the Americas. It is slightly smaller than Lake Titicaca. With an elevation...
belonged to an endemic species, the Lake Nicaragua shark (
Carcharhinus nicaraguensis). In 1961, following
specimenA specimen is a portion/quantity of material for use in testing, examination, or study.BiologyA laboratory specimen is an individual animal, part of an animal, a plant, part of a plant, or a microorganism, used as a representative to study the properties of the whole population of that species or...
s comparisons, taxonomists
synonymizedIn scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...
them. They can jump along the rapids of the
San Juan RiverThe San Juan River , also known as El Desaguadero , is a 192.06 km river that flows east out of Lake Nicaragua into the Caribbean Sea. A large section of the border between Nicaragua and Costa Rica runs on the right bank of the river...
(which connects Lake Nicaragua and the
Caribbean SeaThe Caribbean Sea is a sea of the Atlantic Ocean located in the tropics of the Western hemisphere. It is bounded by Mexico and Central America to the west and southwest, to the north by the Greater Antilles, and to the east by the Lesser Antilles....
), almost like
salmonSalmon is the common name for several species of fish in the family Salmonidae. Several other fish in the same family are called trout; the difference is often said to be that salmon migrate and trout are resident, but this distinction does not strictly hold true...
. Bull sharks tagged inside the lake have later been caught in the open ocean (and
vice versa), with some taking as little as seven to eleven days to complete the journey.
Anatomy and appearance
Bull sharks are large and stout, with females being larger than males. The bull shark can be up to 81 centimetres (2.7 ft) in length at birth and grow up to 3.5 metres (11.5 ft) (though a 13-footer was caught in a South African river) and weigh 318 kilograms (701.1 lb). Bull sharks are wider than other
requiem sharkRequiem sharks are a family, Carcharhinidae, of sharks in the order Carcharhiniformes, containing migratory, live-bearing sharks of warm seas such as the tiger shark, the blue shark, the bull shark, and the milk shark.The name may be related to the French word for shark, "requin", itself of...
s of comparable length, and are grey on top and white below. The second
dorsal finA dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
is smaller than the first. Per the
Discovery Channel and Animal Planet program
Animal Face-OffAnimal Face-Off is a television program that aired on Discovery Channel and Animal Planet in 2004.-Synopsis:This program centers on a hypothetical battle between two animals that could possibly meet in the wild, or in some cases, have been compared to each other by scientists. CGI replicas and...
, bull sharks have a bite force of up to 567 kilograms (1,250 lb).
The bull shark's caudal fin is longer and lower than that of the average shark. It has a small
snoutThe snout, or muzzle, is the protruding portion of an animal's face, consisting of its nose, mouth, and jaw.-Terminology:The term "muzzle", used as a noun, can be ambiguous...
. There is a lack of an interdorsal ridge.
Diet
A bull shark's diet consists mainly of bony fish and sharks, including other bull sharks, but can also include turtles, birds, dolphins, terrestrial mammals,
crustaceanCrustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s and
echinodermEchinoderms are a phylum of marine animals. Echinoderms are found at every ocean depth, from the intertidal zone to the abyssal zone....
s. Bull sharks have been known to use the bump-and-bite technique to attack their prey.
Behavior
Bull sharks are typically solitary hunters, but occasionally hunt in pairs. They often cruise through shallow waters. They can accelerate rapidly and can be highly aggressive, even possibly attacking a racehorse in the
Brisbane RiverThe Brisbane River is the longest river in south east Queensland, Australia, and flows through the city of Brisbane, before emptying into Moreton Bay. John Oxley was the first European to explore the river who named it after the Governor of New South Wales, Thomas Brisbane in 1823...
in the Australian state of
QueenslandQueensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
. They are extremely territorial and attack animals that enter their territory.
Since bull sharks often dwell in very shallow waters, they may be more dangerous to humans than any other species of shark and, along with the
tiger sharkThe tiger sharks, Galeocerdo cuvier, is a species of requiem shark and the only member of the genus Galeocerdo. Commonly known as sea tigers, tiger sharks are relatively large macropredators, capable of attaining a length of over . It is found in many tropical and temperate waters, and is...
and
great white sharkThe great white shark, scientific name Carcharodon carcharias, also known as the great white, white pointer, white shark, or white death, is a large lamniform shark found in coastal surface waters in all major oceans. It is known for its size, with the largest individuals known to have approached...
, are among the three shark species most likely to attack humans.
One or several bull sharks may have been responsible for the
Jersey Shore shark attacks of 1916The Jersey Shore shark attacks of 1916 were a series of shark attacks along the coast of New Jersey between July 1 and July 12, 1916, in which four people were killed and one injured. Since 1916, scholars have debated which shark species was responsible and the number of animals involved, with the...
, which was the inspiration for
Peter BenchleyPeter Bradford Benchley was an American author, best known for his novel Jaws and its subsequent film adaptation, the latter co-written by Benchley and directed by Steven Spielberg...
's novel
JawsJaws is a 1974 novel by Peter Benchley. It tells the story of a great white shark that preys upon a small resort town, and the voyage of three men to kill it....
. The speculation of bull sharks possibly being responsible is based on some attacks occurring in brackish and freshwater as well as there being certain similarities in bite marks between bull and great white sharks.
The bull shark is responsible for attacks around the
Sydney HarbourPort Jackson, containing Sydney Harbour, is the natural harbour of Sydney, Australia. It is known for its beauty, and in particular, as the location of the Sydney Opera House and Sydney Harbour Bridge...
inlets. Most of these attacks were previously attributed to great whites. In India bull sharks swim up the
Ganges RiverThe Ganges or Ganga, , is a trans-boundary river of India and Bangladesh. The river rises in the western Himalayas in the Indian state of Uttarakhand, and flows south and east through the Gangetic Plain of North India into Bangladesh, where it empties into the Bay of Bengal. By discharge it...
and have attacked people. Many of these attacks have been attributed to the
Ganges sharkThe Ganges shark is a rare species of requiem shark found in the Ganges River of India. It should not be confused with the Bull shark, which also inhabits the Ganges River and is sometimes incorrectly referred to as the Ganges shark....
,
Glyphis gangeticus, a critically endangered river shark species that is probably the only other shark in India that can live comfortably in freshwater, although the
grey nurse sharkThe sand tiger shark or grey nurse shark is a species of shark that inhabits coastal waters worldwide. It lives very close to the shorelines and beaches of North America, hence the name, sand tiger shark. Despite a fearsome appearance and strong swimming abilities, it is a relatively placid and...
was also blamed during the sixties and seventies.
Reproduction
Bull sharks mate during late summer and early autumn, often in the brackish water of river mouths. After
gestatingGestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....
for 12 months, a bull shark may give birth to four to ten live young. They are viviparous; they are born live and free-swimming. The young are about 70 cm (27.6 in) at birth and take 10 years to reach maturity. Coastal lagoons, river mouths, and other low-salinity estuaries are common nursery habitats.
Ecology
Bull sharks are
apex predatorApex predators are predators that have no predators of their own, residing at the top of their food chain. Zoologists define predation as the killing and consumption of another organism...
s and rarely have to fear being attacked by other animals. Humans are their biggest threat. Larger sharks, such as the
tiger sharkThe tiger sharks, Galeocerdo cuvier, is a species of requiem shark and the only member of the genus Galeocerdo. Commonly known as sea tigers, tiger sharks are relatively large macropredators, capable of attaining a length of over . It is found in many tropical and temperate waters, and is...
and
great white sharkThe great white shark, scientific name Carcharodon carcharias, also known as the great white, white pointer, white shark, or white death, is a large lamniform shark found in coastal surface waters in all major oceans. It is known for its size, with the largest individuals known to have approached...
, may attack them. There have been stories documented in the media of
saltwater crocodileThe saltwater crocodile, also known as estuarine or Indo-Pacific crocodile, is the largest of all living reptiles...
s preying on young bull sharks in the rivers and estuaries of
Northern AustraliaThe term northern Australia is generally known to include two State and Territories, being Queensland and the Northern Territory . The part of Western Australia north of latitude 26° south—a definition widely used in law and State government policy—is also usually included...
.
See also
External links