Bull shark
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? Bull Shark Conservation status: Lower risk (nt)
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| Carcharhinus leucas ( Müller and Henle, 1839) |
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Bull sharks, Zambezi River Shark or Colloquially Zambi are common in warm, shallow waters along coasts throughout the world. They are, due to their habits, probably responsible for the majority of attacks on humans that take place near shore, including many attacks attributed to other species. Bull sharks can travel inland by swimming up rivers, and have a unique tolerance for fresh water. Those found far from the ocean are the same species as the seaborne bull shark, and are not true freshwater sharks (unlike the river sharks of the genus Glyphis).
Naming
The name, "bull shark," comes from its stocky shape and broad, flat snout. In India, the bull shark is often called the Sunderbans or Ganges shark and is considered a delicacy for Bengali fish curries. In Africa it is often called Zambezi River Shark or just Zambi.
Distribution
The Bull shark is common in costal areas of warm oceans, in rivers and lakes, both in salt and fresh water. In the Atlantic it is found from Massachusetts to South Brazil and from Morocco to Angola, in the Pacific it is found from South Africa to Kenya, India, Vietnam to Australia and from Baja California to Ecuador. They are also found in the central Amazon River, and have been recorded as far up the Mississippi River as Illinois. They are also found in the fresh water Lake Nicaragua and the Ganges and Brahmaputra rivers of West Bengal and Assam in eastern India and adjoining Bangladesh. It is found to a depth of about 30 meters.
Description
Bull sharks are large. The males of this species can reach 2.1 m (6.9 ft) long and weigh 90 kg (198.4 lbs). The females can be much larger, 3.5 m (11.5 ft) long and 230 kg (507 lbs).
Behavior
Bull sharks are mostly sluggish, solitary animals who cruise through shallow waters, taking a wide variety of prey: fish, other sharks, rays, turtles, birds, mollusks, and crustaceans. They seem not to view humans as prey under normal conditions, but will bite out of curiosity or when threatened, or in water where visibility is poor and a human might easily be mistaken for a prey animal. Despite their apparent docility at times, they are capable of surprising bursts of speed, and can be highly aggressive. Their aggression is fueled by testosterone. The bull shark has one of the highest testosterone levels of all animals. Like all sharks, their behaviour is poorly understood and can seem unpredictable.
Attack Patterns
Bull sharks have the ability to navigate shallow and dirty waters and can attack almost anything that is moving or living. A bull shark will generally brush its nose against the prey item before biting. Attacks are usually achieved by surprise, with the shark approaching at a fast speed and colliding with its victim. Maintaining constant underwater eye contact with the shark will reduce the possibility of being attacked.
Reproduction
Breeding takes place in the summer, often in brackish water of river mouths. After a gestation of about a year, bull sharks give birth to as many as 13 live young (they are ovoviviparous). The young are about 70 cm long at birth and take as long as 10 years to reach maturity.