Bull Shark

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Bull Shark

Bull sharks live in the warm coastal waters of the Atlantic, Indian and Pacific oceans and occasionally travel inland through rivers and other freshwater sources. They feed on other sharks, fish, dolphins, turtles, birds and almost any other source of meat they can find. Bull sharks have an average lifespan of 16 years in their natural habitat.


Content List

1. Scientific & Common Names

2. Characteristics

a. Breeding

b. Behavior

3. History

4. Present Status

5. References


Scientific & Common Names

Kingdom - Animalia

Phylum - Chordata

Class - Chondricthyes

Subclass - Elasmobranchii

Order - Carcharhiniformes

Family - Carcharhinidae

Genus - Carcharhinus

Species - C. leucas

Common Names - Bull Shark, Bullhead Shark, Cub Shark, Ground Shark, Lake Nicaragua Shark, Zambezi Shark


Characteristics

Bull sharks have gray upper sides and backs and white bellies. They have broad, stout bodies and a wide snout. It is believed that their common name, which was shortened from "bullhead shark" comes from their stocky build and broad heads. Females are typically bigger than males, with females measuring roughly 11 feet in length and males measuring around 7 feet in length. Adult bull sharks can weigh anywhere from 200 to 500 pounds.


Breeding

Bull sharks mate during summer, and females carry and give birth to live offspring around 12 months later. Bull shark litters have up to 13 pups, which measure about 28 inches when they are born. Young bull sharks typically have dark tips on their fins.


Behavior

Bull sharks are aggressive and considered dangerous to humans, especially since they mainly stay in shallower waters. They are known for attacking their prey by head-butting it first. Bull sharks usually live alone, although groups of them sometimes travel long distances between the Atlantic Ocean and Amazon River. These sharks are notable for their ability to tolerate a greatly reduced salt content in their water, which allows them to travel unusually far into rivers and lake systems. They have been found in rivers in Florida, as well as far up the Mississippi River. Others have been spotted leaping over rapids like salmon in the San Juan River to get into Lake Nicaragua, and have also been seen in Africa's Zambezi River. Previously, these freshwater dwellers were believed to be different species (Lake Nicaragua Shark and Zambezi Shark or "Zambi"), but recent genetic studies have shown them to in fact be bull sharks.


History

Bull sharks have been targeted by commercial fisheries for years for their liver oil, skin and flesh. Although they are still found in their historical range, their populations are becoming more vulnerable due to human encounters and habitat changes. Bull shark can be kept in captivity for many years and are sometimes seen in commercial aquaria.


Present Status

The bull shark is listed as near threatened. Exact numbers for the species aren’t known, but the overall population is thought to be at risk of declining. The main threat to bull sharks is capture by humans for their fins. Other threats include pollution and changes to their natural habitat due to their tendency to travel to inland estuaries and rivers. There are currently no conservation efforts in place that are specifically aimed at protecting this species.


References

   http://animaldiversity.ummz.umich.edu/accounts/Carcharhinus_leucas/
   http://animals.nationalgeographic.com/animals/fish/bull-shark/
   http://www.iucnredlist.org/details/full/39372/0
   Sharks of the World, 2005, Leonard Compagno and Sarah Fowler
   The Sharks of North America, 2011, Jose I. Castro