Bull Shark
Carcharhinus leucas
Description
Bull sharks are distinguished from other sharks by their body’s high width-to-length ratio, giving them a stout appearance. Like many fish, bull sharks exhibit countershading, or dark coloration on top and light coloration on the underbelly. This helps the animals blend into their surroundings—from above, its dark back blends into the murky water below. But from below, its white belly blends into the sunlit waters above. Male bull sharks grow to about seven feet (2.1 meters) in length, and females grow to 11 feet (3.3 meters) or more. Adults usually weigh between 200 and 500 pounds (91 to 227 kilograms).
Range
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. They prefer shallow coastal water, which means they can often come into contact with humans. Bull sharks are often considered to be the most dangerous sharks to humans because of their aggressive tendencies and ability to migrate up rivers. However, shark attacks are extremely rare. In a typical year, fewer than 20 people die by shark attack, but more than 20 million sharks die in relation to the fishing industry.
Diet
The bull shark is not a picky eater. The sharks eat mostly fish, but can also eat other shark species, marine mammals, birds, and turtles. Although rare, bull sharks have also been recorded eating other bull sharks. Adult sharks tend to hunt by themselves.
Life History
Bull sharks rarely come together, except to mate. Offspring are usually born in the spring or summer, except in warm climates where young may be born year-round. Bull sharks usually live for 12 to 16 years, but one bull shark in captivity was recorded living to 30 years old.
Conservation
These fish are listed as near threatened. Because of their coastal distribution, bull sharks are more at risk from pollution and habitat degradation than other species. They are intentionally caught for their fins, liver oil, and skin, and are sometimes caught unintentionally as well. In addition, some bull sharks are caught for display in aquariums.
Fun Fact
Bull sharks have special glands and kidney functions to help their bodies retain salt while in freshwater.
Sources
Animal Diversity Web, University of Michigan Museum of Zoology
Florida Museum of Natural History
National Geographic
The IUCN Red List of Threatened Species
