Zambezi shark, Zambi, Lake nicaragua 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 beachgoers, which is one of the causes of bull shark populations continuing to decrease.
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, 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.
Unlike the river sharks of the genus Glyphis, bull sharks are not true freshwater sharks, despite their ability to survive in freshwater habitats.
This shark is the same one that appears in the image of the 2000 colones bill from Costa Rica.
The name "bull shark" comes from the shark's stocky shape, broad, flat snout, and aggressive, unpredictable behavior. 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, river shark, freshwater whaler, estuary whaler, Swan River whaler, cub shark, and shovelnose shark.
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CarnivoreA carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of a...
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ViviparousAmong animals, viviparity is the development of the embryo inside the body of the parent. The term 'viviparity' and its adjective form 'viviparous'...
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starts withBull 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. 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). A 3.25 m (10.7 ft) long pregnant individual reached 450 kg (990 lb). The maximum weight can be over 600 kg (1,300 lb), ranking it among the largest of the requiem sharks. 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.
Bull sharks have a bite force up to 5,914 newtons (1,330 lbf), weight for weight the highest among all investigated cartilaginous fishes.
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). 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. Several were sighted in one of the main streets of Goodna, Queensland, shortly after the peak of the January 2011, floods. 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. 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 and north Bolivia. It also lives in freshwater Lake Nicaragua, in the Ganges and Brahmaputra Rivers of West Bengal, and Assam in Eastern India and adjoining Bangladesh. 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, and has been rumored to also inhabit the Cahora Bassa lake upstream of the Zambezi. The species has a distinct preference for warm currents.
After Hurricane Katrina, many bull sharks were sighted in Lake Pontchartrain. In July 2023 some local fishermen in the Atchafalaya River have reported increasing numbers. Bull sharks have occasionally gone as far upstream in the Mississippi River as Alton, Illinois. Bull sharks have also been found in the Potomac River in Maryland. A golf course lake at Carbrook, 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. The golf course has capitalized on the novelty and now hosts a monthly tournament called the "Shark Lake Challenge".
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. 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, and a Nile crocodile was reportedly sighted consuming a bull shark in South Africa.
The bull shark is a marine apex predator, capable of taking a variety of prey. The bull shark's diet consists mainly of bony fish and small sharks, including other bull sharks, 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. 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.
The bull shark is a solitary hunter, though may briefly pair with another bull shark to make hunting and tricking prey easier.
Sharks are opportunistic feeders, 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. 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.
Bull sharks mate during late summer and early autumn, often in bays and estuaries. After gestating for 12 months, a bull shark may give birth to 1 to 13 live young.
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. Coastal lagoons, river mouths, and other low-salinity estuaries are common nursery habitats.
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. 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.
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. 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. 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.
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. Bull sharks are one of the three shark species (along with the tiger shark and great white shark) most likely to bite humans.
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. 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. 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.
