where bull sharks live?

Carcharhinus leucas

These large stout sharks are found in both salt and fresh water. They have been recorded in rivers hundreds of miles from the sea but are most commonly found in marine, estuarine environments close to shore (Simpfendorfer and Burgess 2009). Bull sharks can grow to a total length of about 340 cm. Like most of the requiem sharks in the genus Carcharhinus, Bull sharks are plain grey above, with a pale to white underbelly. They have broad, rounded snouts and small eyes (Compagno et al. 2005). They are opportunistic feeders targeting bony fishes, sharks, turtles, birds, dolphins and terrestrial mammals.

Fun Fact: Bull sharks were blamed for a series of attacks in 1916, which served inspiration for Peter Benchley’s book Jaws, which Steven Spielberg turned into a blockbuster movie in 1975.

The bull shark name derives from its stout appearance and reputation for aggressive behavior. It is known by many different common names throughout its range including requin bouledogue in French speaking countries; Tiburon sarda in Spain; Zambezi shark, Van Rooyen’s shark in South Africa; The Ganges shark in India (though this name is also given to the freshwater river shark Glyphis gangeticus); The Nicaragua shark in Central America; The freshwater whaler, estuary whaler, and Swan River whaler in Australia; The shovelnose shark, square-nose shark, river shark, slipway grey shark, ground shark, and cub shark in various English speaking parts of the world.

Though the bull shark is not a targeted species in most commercial fisheries, it is regularly captured on bottom longline gear. In the commercial shark fishery in the southeastern U.S., in the 1990’s, the Bull shark comprised 1-6% of the large coastal shark catch. (Branstetter and Burgess 1997). It is more often targeted in small artisanal fisheries because of its abundance in nearshore environments. The meat is either used for fish meal or sold in local markets for human consumption. The fins are used in Asia for shark fin soup while the skin is frequently used for leather (Simfendorder and Burgess 2009).

The bull shark is considered a game fish in the southeastern U.S. and South Africa, and is fished by rod and reel from shore, piers, and bridges. According to the International Game Fish Association (IGFA), the largest bull shark caught on rod and reel weighed 771 lb. 9 oz. (347 kg) and was caught near Cairns, Australia. Bull sharks are frequently observed at recreational shark feeding dives in the Caribbean.

Bull sharks adapt well to being kept in captivity and are on exhibit in a number of public aquaria. Some have been kept in tanks for over 15 years (Compagno et al. 2005). Although there is no current evidence that aquarium collecting has had an impact on the wild population of bull sharks, the demand for sharks in the aquarium industry has grown substantially over the past 20 years

According to the International Shark Attack File (ISAF), bull sharks are historically responsible for at least 100 unprovoked attacks on humans around the world, 27 of which have been fatal. However, it is likely that this species may responsible for many more. It is considered by many to be the most dangerous shark in the world. It’s large size, proclivity for freshwater, abundance and proximity to human populations, particularly in the tropics, makes it more of a potential threat than is either the White shark or the Tiger shark. Since the bull shark occurs in several underdeveloped regions of the world including Central America, Mexico, India, East and West Africa, the Middle East, Southeast Asia, and the South Pacific, bites often go unreported. The Bull shark is also not as readily identified as is the white shark or the tiger shark, and so may be responsible for a large fraction of the of the attacks that go unassigned to species (ISAF 2018).

The bull shark is considered the likely culprit for the infamous series of five attacks that occurred in New Jersey in 1916 that resulted in four fatalities over a 12 day period. Three of these attacks occurred in Matawan Creek, a shallow tidal river, only 40 feet (12 m) across, 1.5 miles (2.4 km) from bay waters, and over 15 miles (24 km) from the open ocean; not a location where any other large shark species would likely occur. A 7.5 foot (2.25 m) white shark was captured two days after the last attack, 4 miles (6.4 km) from the mouth of Matawan Creek, and allegedly contained human remains in its stomach. A 9 foot (2.7 m) bull shark was also captured a day later only 10 miles (16 km) from Matawan. This has been a topic of controversy for many years, and there is evidence that points to the involvement of both the bull shark and the white shark. It has not yet been conclusively resolved. (ISAF 2018).

IUCN Red List Status: Near Threatened

Though the Bull shark is not a targeted species, it is routinely caught in fisheries around the world. Because it lives in estuarine and inshore regions, close to human populations, it is vulnerable to human impact. The inshore nursery grounds are particularly at risk. The Natal Sharks Board reports that the average size of bull sharks caught in their beach nets have significantly declined in recent years, which does not bode well for South African populations of the species. The bull shark is not currently legally protected in any part of its range. Further research is necessary to better characterize its biological, ecological, and fisheries significance (Simpfendorfer and Burgess 2009).

> Check the status of the bull shark at the IUCN website.

The IUCN is a global union of states, governmental agencies, and non-governmental organizations in a partnership that assesses the conservation status of species.

Bull sharks occur in tropical to subtropical coastal waters, worldwide. They also occur in a number of river systems and some freshwater lakes (Compagno et al. 2005). They have been reported 3700 km (2220 mi) up the Amazon River in Peru, and over 3000 km (1800 mi) up the Mississippi River, in Illinois. A population in Lake Nicaragua (Central America) was once thought to be landlocked, but it was subsequently determined that they gain access to the ocean through a system of rivers and estuaries. In the western Atlantic, bull sharks migrate north along the coast of the U.S. during summer, swimming as far north as Massachusetts, and then return to tropical climates when the coastal waters cool (Simpfendorfer and Burgess 2009).

The bull shark prefers to live in shallow coastal waters less than 100 feet deep (30 m), but ranges from 3-450 feet deep (1-150 m). It commonly enters estuaries, bays, harbors, lagoons, and river mouths. It is one of very few species that readily move into freshwater, and apparently can spend long periods of time in such environments (Sharks of the Genus Glyphis are also capable of living in freshwater). There is evidence that while they can breed in freshwater, they do not do so as regularly as they do in estuarine and marine habitats. Juvenile bull sharks enter low salinity estuaries and lagoons as readily as adults do and use these shallow areas as nursery grounds. Bull sharks can also tolerate hypersaline water as high as 53 parts per thousand (Simpfendorfer and Burgess 2009).

1. First dorsal large and triangular

2. First dorsal fin originates over or slightly behind pectoral insertion

3. Snout is much shorter than width of mouth and bluntly rounded

4. Eyes are small

Distinctive Features Bull sharks are very stout-bodied and have a blunt, rounded snout. They lack an interdorsal ridge. The first dorsal fin is large and broadly triangular with a pointed apex. The second dorsal fin is significantly smaller. The pectoral fins are also large, broad and angular. Bull sharks have small eyes relative to most other carcharhinid sharks which suggests that vision may not be as important for this species which often occurs in turbid waters.

Coloration Bull sharks are pale to dark gray above, fading to a pale cream color on their underside. In younger individuals the fins have dark tips which fade to a more diffuse dusky color as they grow.

Dentition Upper jaw teeth of the bull shark are broad, triangular, and heavily serrated. Lower jaw teeth have a broad base, and are narrow and triangular with fine serrations. Anterior teeth are erect and nearly symmetrical, while posterior teeth become more oblique in shape.

Size, Age & Growth The maximum reported length of the bull shark is 400 cm (~13 ft) (Compagno et al. 1995) and maximum reported weight is 316.5 kg (~698 pounds) (IGFA 2001). Size at birth is 56-81 cm (~2-3 ft) and size at maturity is 157-226 cm (~5-7 ft) for males and 180-230 cm (~6-7.5 ft) for females (Simpfendorfer and Burgess 2009). Age of maturity is between 15-20 years and the known lifespan is >25 years (Compagno et al. 2005). Growth rates have been calculated by Thorson and Lacy (1982) using tag recapture information in Lake Nicaragua. They estimated that in the first two years, the growth rate is about 16-18cm per year. A later study by Branstetter and Stiles (1987) estimate that this growth rate subsequently slows to 4-5 cm per year.

Food Habits Bony fishes and small sharks make up the vast majority of the bull shark’s diet. In the western Atlantic they commonly feed on mullet, tarpon, catfishes, menhaden, gar, snook, jacks, mackerel, snappers, and other schooling fish. They also consume stingrays and juvenile sharks including small individuals of their own species in their inshore nursery habitats. Other food items occasionally reported in bull sharks include sea turtles, dolphins, crabs, shrimp, sea birds, squid, and dogs. Bull sharks appear sluggish as they cruise slowly along the bottom, but are capable of quick bursts that allow them to capture smaller, agile prey. They have been recorded to move at over 11 mph (19 km/h) over short distances.

Reproduction Age of maturation for female bull sharks is estimated to be 18 years (6-7.5 feet (180-230 cm) total length, TL) and 14-15 years (5.1-7.41 feet (157-226 cm) TL) for males (Branstetter and Stiles 1987).

Bull sharks bear live young. The developing pups (one to thirteen per litter) are nourished internally via a yolk-sac placenta. The mother gives birth after a 10-11 month gestation period at which point they become free-swimming and autonomous. In the Gulf of Mexico mating occurs during summer months, and the pups are born the following April-June. Mating and birthing occurs year-round in the warmest parts of the range. Females often bear mating scars on their flanks. Coastal lagoons, river mouths, and other low-salinity estuaries are common nursery habitats (Simpfendorfer and Burgess 2009).

Predators Adult bull sharks have few natural predators. Young bull sharks, however, can fall prey to tiger sharks (Galeocerdo cuvier), sandbar sharks (Carcharhinus plumbeus), and other Bull sharks. A crocodile in South Africa was also reported to have consumed a bull shark.

The bull shark (Carcharhinus leucas), also known as the Zambezi shark (informally zambi) in Africa and Lake Nicaragua shark in Nicaragua, is a species of requiem shark commonly found worldwide in warm, shallow waters along coasts and in rivers. It is known for its aggressive nature, and presence mainly in warm, shallow brackish and freshwater systems including estuaries and (usually) lower reaches of rivers. This aggressive nature is a reason for its population being listed as vulnerable on the IUCN Red List. Shark-culling occurs near beaches to protect beach goers, which is one of the causes of bull shark populations continuing to decrease.[3]

Bull sharks are euryhaline and can thrive in both salt and fresh water. They are known to travel far up rivers, and have been known to travel up the Mississippi River as far as Alton, Illinois,[4] about 1,100 kilometres (700 mi) from the ocean, but few freshwater interactions with humans have been recorded. Larger-sized bull sharks are probably responsible for the majority of nearshore shark attacks, including many incidents of shark bites attributed to other species.[5]

Unlike the river sharks of the genus Glyphis, bull sharks are not true freshwater sharks, despite their ability to survive in freshwater habitats.

The name "bull shark" comes from the shark's stocky shape, broad, flat snout, and aggressive, unpredictable behavior.[6] In India, the bull shark may be confused with the Sundarbans or Ganges shark. In Africa, it is also commonly called the Zambezi River 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,[7] river shark, freshwater whaler, estuary whaler, Swan River whaler,[8] cub shark, and shovelnose shark.[9]

Some of the bull shark's closest living relatives do not have the capabilities of osmoregulation. Its genus, Carcharhinus, also includes the sandbar shark, which is not capable of osmoregulation.[10]

The bull shark shares numerous similarities with river sharks of the genus Glyphis, and other species in the genus Carcharhinus, but its phylogeny has not been cleared yet.[11]

Bull sharks are large and stout, with females being larger than males. The bull shark can be up to 81 cm (2 ft 8 in) in length at birth.[12] Adult female bull sharks average 2.4 m (8 ft) long and typically weigh 130 kg (290 lb), whereas the slightly smaller adult male averages 2.25 m (7 ft) and 95 kg (209 lb). While a maximum size of 3.5 m (11 ft) is commonly reported, a single record exists of a female specimen of exactly 4.0 m (13 ft).[5][13][14] A 3.25 m (10.7 ft) long pregnant individual reached 450 kg (990 lb).[15] Bull sharks are wider and heavier than other requiem sharks of comparable length, and are grey on top and white below. The second dorsal fin is smaller than the first. The bull shark's caudal fin is longer and lower than that of the larger sharks, and it has a small snout, and lacks an interdorsal ridge.[12]

Bull sharks have a bite force up to 5,914 newtons (1,330 lbf), weight for weight the highest among all investigated cartilaginous fishes.[16]

In early June 2012, off the coast of the Florida Keys near the western part of the Atlantic Ocean, a female believed to measure at least 2.4 m (8 ft) and 360–390 kg (800–850 lb) was caught by members of the R.J. Dunlap Marine Conservation Program.[13][14] In the Arabian Sea, off the coast of Fujairah in the United Arab Emirates, a pregnant shark weighing 347.8 kg (767 lb) and measuring 3 m (10 ft) long was caught in February 2019,[17][18] followed by another specimen weighing about 350 kg (770 lb) and measuring about the same in length, in January 2020.[19][20]

The bull shark is commonly found worldwide in coastal areas of warm oceans, in rivers and lakes, and occasionally salt and freshwater streams if they are deep enough. It is found to a depth of 150 m (490 ft), but does not usually swim deeper than 30 m (98 ft).[21] In the Atlantic, it is found from Massachusetts to southern Brazil, and from Morocco to Angola.

Populations of bull sharks are also found in several major rivers, with more than 500 bull sharks thought to be living in the Brisbane River. One was reportedly seen swimming the flooded streets of Brisbane, Queensland, Australia, during the 2010–11 Queensland floods.[22] Several were sighted in one of the main streets of Goodna, Queensland, shortly after the peak of the January 2011, floods.[23] A large bull shark was caught in the canals of Scarborough, just north of Brisbane within Moreton Bay. Still greater numbers are in the canals of the Gold Coast, Queensland.[24] In the Pacific Ocean, it can be found from Baja California to Ecuador.

The bull shark has traveled 4,000 km (2,500 mi) up the Amazon River to Iquitos in Peru[25] and north Bolivia.[2] It also lives in freshwater Lake Nicaragua, in the Ganges and Brahmaputra Rivers of West Bengal, and Assam in Eastern India and adjoining Bangladesh.[citation needed] It can live in water with a high salt content as in St. Lucia Estuary in South Africa. Bull sharks have been recorded in the Tigris River since at least 1924 as far upriver as Baghdad.[26] The species has a distinct preference for warm currents.[citation needed]

After Hurricane Katrina, many bull sharks were sighted in Lake Pontchartrain.[27] Bull sharks have occasionally gone as far upstream in the Mississippi River as Alton, Illinois.[28] Bull sharks have also been found in the Potomac River in Maryland.[29][30] A golf course lake at Carbook, Logan City, Queensland, Australia is the home to several bull sharks. They were trapped following a flood of the Logan and Albert Rivers in 1996.[31] The golf course has capitalized on the novelty and now hosts a monthly tournament called the "Shark Lake Challenge".[32]

The bull shark is the best known of 43 species of elasmobranch in 10 genera and four families to have been reported in fresh water.[33] Other species that enter rivers include the stingrays (Dasyatidae, Potamotrygonidae and others) and sawfish (Pristidae). Some skates (Rajidae), smooth dogfishes (Triakidae), and sandbar sharks (Carcharhinus plumbeus) regularly enter estuaries.[citation needed]

The bull shark is diadromous, meaning they can swim between salt and fresh water with ease.[34] These fish also are euryhaline fish, able to adapt to a wide range of salinities. The bull shark is one of the few cartilaginous fishes that have been reported in freshwater systems. Many of the euryhaline fish are bony fish such as salmon and tilapia and are not closely related to bull sharks. Evolutionary assumptions can be made to help explain this sort of evolutionary disconnect, one being that the bull shark encountered a population bottleneck that occurred during the last ice age.[35] This bottleneck may have separated the bull shark from the rest of the Elasmobranchii subclass and favored the genes for an osmoregulatory system.

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 urea and trimethylamine oxide, but bull sharks living in fresh water show a significantly reduced concentration of urea within their blood.[36] Despite this, the solute composition (i.e. osmolarity) of a bull shark in fresh water is still much higher than that of the external environment. This results in a large influx of water across the gills due to osmosis and loss of sodium and chloride from the shark's body. However, bull sharks in fresh water possess several organs with which to maintain appropriate salt and water balance; these are the rectal gland, kidneys, liver, and gills. All elasmobranchs have a rectal gland which functions in the excretion of excess salts accumulated as a consequence of living in seawater. Bull sharks in freshwater environments decrease the salt-excretory activity of the rectal gland, thereby conserving sodium and chloride.[37] The kidneys produce large amounts of dilute urine, but also play an important role in the active reabsorption of solutes into the blood.[37] The gills of bull sharks are likely to be involved in the uptake of sodium and chloride from the surrounding fresh water,[38] whereas urea is produced in the liver as required with changes in environmental salinity.[39] Recent work also shows that the differences in density of fresh water to that of marine waters result in significantly greater negative buoyancies in sharks occupying fresh water, resulting in increasing costs of living in fresh water. Bull sharks caught in freshwater have subsequently been shown to have lower liver densities than sharks living in marine waters. This may reduce the added cost of greater negative buoyancy.[40]

Bull sharks are able to regulate themselves to live in either fresh or salt water. It can live in fresh water for its entire life, but this does not happen, mostly due to the reproductive needs of the shark. Young bull sharks leave the brackish water in which they are born and move out into the sea to breed. Whilst it is theoretically possible for bull sharks to live purely in fresh water, experiments conducted on bull sharks found that they died within four years. The stomach was opened and all that was found were two small, unidentifiable fishes. The cause of death could have been starvation since the primary food source for bull sharks resides in salt water.[41]

In a research experiment, the bull sharks were found to be at the mouth of an estuary for the majority of the time.[34] They stayed at the mouth of the river independent of the salinity of the water. The driving factor for a bull shark to be in fresh or salt water, however, is its age; as the bull shark ages, its tolerance for very low or high salinity increases.[34] The majority of the newborn or very young bull sharks were found in the freshwater area, whereas the much older bull sharks were found to be in the saltwater areas, as they had developed a much better tolerance for the salinity.[34] Reproduction is one of the reasons why adult bull sharks travel into the river—it is thought to be a physiological strategy to improve juvenile survival and a way to increase overall fitness of bull sharks.[34] The young are not born with a high tolerance for high salinity, so they are born in fresh water and stay there until they are able to travel out.

Initially, scientists thought the sharks in Lake Nicaragua belonged to an endemic species, the Lake Nicaragua shark (Carcharhinus nicaraguensis). In 1961, following specimen comparisons, taxonomists synonymized them.[42] Bull sharks tagged inside the lake have later been caught in the open ocean (and vice versa), with some taking as few as seven to 11 days to complete the journey.[42]

The bull shark's diet consists mainly of bony fish and small sharks, including other bull sharks,[5] and stingrays. Their diet can also include turtles, birds, dolphins, terrestrial mammals, crustaceans, and echinoderms. They hunt in murky waters where it is harder for the prey to see the shark coming.[2][43][44] Bull sharks have been known to use the bump-and-bite technique to attack their prey. After the first initial contact, they continue to bite and tackle prey until the prey is unable to flee.[45]

The bull shark is a solitary hunter, though may briefly pair with another bull shark to make hunting and tricking prey easier.[46][47]

Sharks are opportunistic feeders,[45] and the bull shark is no exception to this, as it is part of the Carcharhinus family of sharks. Normally, sharks eat in short bursts, and when food is scarce, sharks digest for a much longer period of time in order to avoid starvation.[45] As part of their survival mechanism, bull sharks will regurgitate the food in their stomachs in order to escape from a predator. This is a distraction tactic; if the predator moves to eat the regurgitated food the bull shark can use the opportunity to escape.[48]

Bull sharks mate during late summer and early autumn,[10] often in bays and estuaries.[49] After gestating for 12 months, a bull shark may give birth to 1 to 13 live young.[10][50]

They are viviparous, born live and free-swimming. The young are about 70 cm (27.6 in) at birth. The bull shark does not rear its young; the young bull sharks are born into flat, protected areas.[50] Coastal lagoons, river mouths, and other low-salinity estuaries are common nursery habitats.[5]

The male bull shark is able to begin reproducing around the age of 15 years while the female cannot begin reproducing until the age of 18 years.[50] The size of a fully matured female bull shark to produce viable eggs for fertilization seems to be 175 cm to 235 cm. The courting routine between bull sharks has not been observed in detail as of yet. The male likely bites the female on the tail until she can turn upside down and the male can copulate at that point. Mature females commonly have scratches from the mating process.[51]

Since bull sharks often dwell in very shallow waters, are found in many types of habitats, are territorial by nature, and have no tolerance for provocation, they may be more dangerous to humans than any other species of shark.[21] Bull sharks are one of the three shark species (along with the tiger shark and great white shark) most likely to bite humans.[6]

One or several bull sharks may have been responsible for the Jersey Shore shark attacks of 1916, which were the inspiration for Peter Benchley's novel Jaws.[52] The speculation that bull sharks may have been responsible is based on two fatal bites occurring in brackish and fresh water.

Bull sharks have attacked swimmers around the Sydney Harbour inlets.[53] In India, bull sharks swim up the Ganges, Bramaputra, Mahanadi, and other Indian rivers and have bitten bathers. Many of these bite incidents were attributed to the Ganges shark, Glyphis gangeticus, a critically endangered river shark species, although the sand tiger shark was also blamed during the 1960s and 1970s.

Bull sharks have also attacked humans off the coast of Florida.[54]

Behavioral studies have confirmed that sharks can take visual cues to discriminate between different objects. The bull shark is able to discriminate between colors of mesh netting that is present underwater. It was found that bull sharks tended to avoid mesh netting of bright colors rather than colors that blended in with the water. Bright yellow mesh netting was found to be easily avoided when it was placed in the path of the bull shark. This was found to be the reason that sharks are attracted to bright yellow survival gear rather than ones that were painted black.[55]

In 2008, researchers tagged and recorded the movements of young bull sharks in the Caloosahatchee River estuary. They were testing to find out what determined the movement of the young bull sharks.[56] It was found that the young bull sharks synchronously moved downriver when the environmental conditions changed.[56] This large movement of young bull sharks were found to be moving as a response rather than other external factors such as predators. The movement was found to be directly related to the bull shark conserving energy for itself. One way the bull shark is able to conserve energy is that when the tidal flow changes, the bull shark uses the tidal flow in order to conserve energy as it moves downriver.[56] Another way for the bull shark to conserve energy is to decrease the amount of energy needed to osmoregulate the surrounding environment.[56]

Humans are the biggest threat to bull sharks. Larger sharks, such as the tiger shark and great white shark, may attack them, but typically only target juveniles.[5] Crocodiles may be a threat to bull sharks in rivers. Saltwater crocodiles have been observed preying on bull sharks in the rivers and estuaries of Northern Australia,[57] and a Nile crocodile was reportedly sighted consuming a bull shark in South Africa.[58]

The bull shark is listed as a vulnerable species on the IUCN Red List and the population is currently reported as decreasing. Despite their status, the species isn't named as a protected species. Threats to the bull shark are numerous, such as getting caught in fishing nets, overfishing for their oil, skin, and meat, pollution to their habitat, and more.[59] In many areas of the world, including Australia and South Africa, there are shark-culling measures around beaches to prevent attacks on beach-goers. Researchers tried to fix the problem of sharks getting too close to land by testing out a device called the SharkSafe Barrier™. This barrier used magnetic and visual stimuli, which utilized rows of piping to create a continuous magnetic field to deter the sharks. However, researchers concluded that the technology needs to be improved upon and tested further before it can be implemented as a reliable safety measure.[3] Other research is being conducted to come up with conservation solutions for the bull sharks. One example is The Nature Conservancy satellite tagging sharks to track their migration and find their habitats in order to guide what areas require further protection projects.[60]

Bull sharks are found in coastal waters all over the world. In the United States they are found off the East Coast and in the Gulf of Mexico. Unlike most sharks, bull sharks can survive in freshwater for long periods of time. They have even been found in the Mississippi and Amazon Rivers.

Photo: Steve Woods

The Bull shark (Carcharhinus leucas) also known as the Zambezi shark in South Africa, can be found in warm shallow waters throughout the world. Unlike most shark species, bull sharks have the ability to swim and survive in fresh water and can be found thousands of miles up rivers. Bull sharks owe their name to the sturdy form of their body and their unpredictable behavior.

Bull sharks are not very long sharks, but they tend to be very thick and stocky. The average size of an adult Bull shark is about 2.3meters in length and 130kg in weight, but specimens have been found up to 3.5meters long and weighing about 300kg. Like most sharks, they have counter shading meaning that they are grey on top and white on the bottom. Bull sharks have a broad, flat snout which is not very long. They have two triangular shaped dorsal fins, but no inter-dorsal ridge.

A key feature that separates bull sharks from most shark species is their rectal gland. The rectal gland is used for storing and excreting salt from the body, which allows them to control their salinity levels even when they are in freshwater environments.

Bull sharks are generally found in warm, shallow waters with temperatures around 32 degrees Celsius. They are found along the coasts of southern North America, Central America, South America, Africa, the Indian Ocean, as well as the Indo-Pacific near Southeast Asia. Specimens have been reported being seen nearly 2,000 miles up the Amazon and Mississippi rivers as well as being in golf course lakes after floods.

Due to their ability to feed in both freshwater and salt-water environments, bull sharks feed on a vast array of prey species. They feed on numerous bony fish, stingrays, other sharks, birds, turtles, crustaceans, and some mammals. They tend to hunt in murky waters because it allows them to sneak up on their prey. They’ve developed a unique hunting method; bull sharks first bump into their prey and then they bite. Pound for pound, Bull sharks have the strongest bite force compared to all shark species.

Bull sharks are viviparous, meaning that they give birth to free-swimming young. They have a gestation period of about one year and can give birth to one to twelve young per birthing. When they are born, adolescent bull sharks are around 65 to 75 centimeters long. They reach sexual maturity after around fifteen years and are about 270 centimeters long at this age.

Bull sharks are listed as Near Threatened by the International Union for Conservation of Nature (IUCN Red List). Bull sharks have long gestation periods, reach sexual maturity at a late age, and give birth to few young making them vulnerable to intense fishing and hunting pressures. They are harvested for their fins and meat, which are used to make the prized Chinese dish shark fin soup. Due to their role as apex predators, Bull sharks are very important to the environments they inhabit and are a necessity for a healthy reef and ecosystem.

Bull sharks are often found in shallow waters along coastal areas and rivers therefore it’s likely that there will be an encounter between these sharks and humans. There are many registered attacks on humans by this shark - according to the international Shark Attack file the bull shark is the third species with most attacks on humans. Only great white sharks and tiger sharks have more registered attacks on humans.

Originally written by Elizabeth Ward-Sing and edited by Isabelle Walter

#BullShark #Shark #CarcharhinusLeucas #FreshwaterShark #NearThreatened #IUCN #Conservation #SharkEducation

But this shark is also known as one of the top 3 sharks most likely to attack humans (the other 2 are the Great White Shark and the Tiger Shark). Of course, we know that shark attacks are extremely rare (less than 4.5 deaths by shark attacks per year globally), but nonetheless, this shark has been nicknamed “The Pit Bull of the Sea” because if its aggressive behavior.

Most sharks have the same salt concentration in the blood as the sea water they are swimming in. This isn’t the case with Bull Sharks. Instead, they only have 50% of the salt concentration in their blood. This makes them very special as they are able to switch from saltwater to freshwater very easily. The only consequence is they produce 20 times more urine when swimming in fresh water.

After about 10 years, they reach maturity. Adults are normally about 3.5 meters (11 feet) long and weigh approximately 300 kilograms (660 pounds). Typically, females are larger than makes and generally live longer. Most males live for about 13 years, while females live to about 17 years of age.

These special hunters are migrants. They are found in many various areas including Oceans, rivers, and even some fresh water lakes! They tend to stay in warm and moderately deep waters around 30 to 150 meters (150 to 500ft) deep.

It seems the Bull Shark favors the Atlantic, Indian, and Pacific Oceans. Some of their favorite rivers include the Brisbane River, Amazon River, Ganges River, Barhamputra River, Potomac River and the Mississippi River. They have been spotted several hundred miles upstream in these rivers, but typically stay within 100 miles of the Ocean. No attacks on humans have ever been recorded in these rivers.

They are in fresh water lakes, too! It’s not too uncommon to see them in Lake Nicaragua and Lake Ponchartrain, just to name a couple. But if there is easy access from a river and the lake is deep enough (about 30 meters or 150 feet), they’ll check it out and maybe even make themselves at home for a while.

This is one of the more social species and sometimes even hunt in groups. There is still quite a bit of mystery surrounding their social structure, but it seems females tend to have dominance over males.

The Bull Shark is known to eat almost anything. The preferred prey includes bony fish, small sharks, turtles, birds, and some species of dolphins.

These sharks are Viviparous, which means pup sharks develop in the womb of its mother, similar to humans. Typically, the pregnancy period is about 1 year, usually during the summer months but sometimes in early autumn as well. Pups are about 60cm (24in) and mothers give birth to 5 to 15 pups at once.

While the Bull Shark is one of just 3 shark species to attack humans unprovoked, attacks are extremely rare. Especially when you consider that thousands of people wash their bodies daily in the Ganges River for religious purposes. This just so happens to be a preferred area for the shark.

This species is not hunted much by humans. The biggest human threat to these creatures are getting caught in fish nets.

Bull sharks are so named because their thick, stout body and short, blunt snout give them the appearance of a bull. They’re also rather aggressive and bull-headed, and they like to bully their prey with head butts before they eat it.

Bull Sharks are medium-sized sharks that can grow up to 11 feet long and weigh about 700 pounds, although females generally top out at 5 feet and males usually reach 7 feet in length. They’re gray on top and white on bottom so that they’re camouflaged against the dark depths when prey is above them, and they blend in to the lighter surface when prey is below them.

Bull Sharks are pretty fascinating creatures, as you’re about to see:

1. Bull Sharks have lots and lots of teeth

All sharks have jaws that are filled with sharp, serrated teeth. The teeth are in rows that act like conveyor belts. When one tooth is lost, the tooth behind it moves forward, sometimes as quickly as within a day, to replace the lost one. A shark may lose and re-grow more than 20,000 teeth over the course of its lifetime!

The average number of rows of teeth in a shark’s jaw is 15, but the Bull Shark isn’t your average shark. It’s certainly not a bull you want to run with: The Bull Shark has around 50 rows of teeth in its jaws, and each row has about 7 teeth, for a grand total of around 350 teeth in its mouth at any given time.

2. Bull sharks enjoy fresh water as much as salt water

Sharks have to have salt in their body for survival. When excess accumulations of salt build up in the body, a rectal gland excretes the excess. The rectal gland of the Bull Shark is less active than that of other sharks, which makes them able to live in fresh water. When their body needs more salt, the liver gets to work producing urea, which allows them to adapt to any change in salinity.

Bull Sharks have been known to inhabit rivers and freshwater lakes. In fact, a Bull Shark was spotted in Illinois after swimming up the Mississippi River, and another swam 2,000 miles up the Amazon River in Peru.

In Queensland, Australia, there’s a golf course with a large freshwater lake that’s home to a school of Bull Sharks who were trapped there after a flood in the ’90s. The golf course is popular among local golfers for the monthly tournament called the “Shark Lake Challenge.”

3. Bull Sharks give birth to live young

Sharks give birth in one of three ways. If they’re oviparous, they lay a sac full of eggs (called a “mermaid’s purse”), which attaches itself to a rock or other surface until the eggs are ready to hatch. If they’re viviparous, they gestate live shark pups and then give birth to them live. If they’re ovoviviparous, they develop eggs, which hatch in the womb. The newly hatched sharks are birthed live.

Bull Sharks are viviparous, and a female shark will have between four and 10 sharks per litter. The gestation period for Bull Sharks is 12 months, after which they give birth in fresh water because the pups are born with a low tolerance for salinity. Bull Shark pups are about two feet long when they’re born, and once they develop a little, they swim out to sea.

Bull Sharks have a lifespan of about 12 years in the wild.

4. Bull Sharks are considered by many experts to be the most dangerous shark

Tiger sharks and great white sharks join the Bull Shark as the Trinity of Terror, the three sharks identified as the most frequent attackers of humans. In fact, the Bull Shark was likely responsible for the 1919 attacks that inspired the movie Jaws, which increased the number of cases of severe galeophobia, or the fear of sharks, from a handful to a nation full.

Bull Sharks like warm waters near the shore, much like humans. They’re common, and aggressive, also like humans, and they’re agile and pretty fast, reaching speeds of up to 12 miles per hour. But much like the great white shark, Bull Sharks rarely actually eat humans, but rather bump ‘n’ bite ’em out of curiosity. Once they get a nibble, they roll their eyes in indignation and swim off to find something edible. (The tiger shark, on the other hand, will eat just about anything.)

Unfortunately for those humans who are “tasted,” the Bull Shark has the highest bite force among all sharks, so that little nibble comes at a force of 1,300 pounds per foot.

5. But humans are more dangerous to the Bull Shark than the Bull Shark is to humans

Bull Sharks are classified as “near endangered” on the IUCN’s Red List. Although Bull Sharks are very commonly seen by humans due to their habitat, their numbers are dwindling due to over-fishing of sharks in general, and particularly sharks that are easy to catch or trap, such as those that live in shallow waters near shore.

Bull Sharks and other species are killed for their fins, liver oils, and skin. The fins are used for the Asian delicacy shark fin soup, and the liver oil finds its way into cosmetics and vitamins. The skin is used for accessories like sharkskin belts and boots. But is a bowl of fin soup or a smooth lipstick worth devastating entire shark species? Some seem to think so.

But the fact is, scientists very recently estimated that humans kill an astonishing 100 to 273 million sharks every year. If we split the change and call it 200 million sharks, that adds up to 380 sharks killed every minute of every day. In the time it takes you to say the word “shark!” six sharks have been killed.

Compare those numbers to the 16 people who are attacked by sharks every year and the one person who dies from a shark attack every two years, and it’s easy to see who’s really the most dangerous predator in the ocean.