Bull sharks have been found in the western Atlantic from Massachusetts to southern Brazil. They have been found in the Indo-West Pacific from Kenya and South Africa to India, and from Vietnam to Australia. They have also been found in the eastern Pacific from southern Baja California, Mexico, to Ecuador. In the western Atlantic, bull sharks travel north along the coast of the United States in summer.

Bull sharks can grow to a total length of about 340 centimetres. Bull sharks have been recorded covering up to 180 kilometres in 24 hours. Over short distances, they have been recorded swimming at about 19 kilometres an hour (about 11 miles an hour). A bull shark often swims slowly near the bottom until prey appears.

Bull sharks have been found hundreds of kilometres from the sea. They have been reported more than 2,000 miles up the Amazon River, in Peru, and as far up the Mississippi River as Illinois. They have also been recorded repeatedly in the Potomac River. Bull sharks, especially young ones, can travel far up rivers.

A bull shark can adjust the salt and water balance in its body, so it can handle sea water and fresh water. Its gills, rectal gland, blood, hormones and kidneys all play a part in managing salt as it moves between salt and fresh water. Bull sharks caught in fresh water had lower salt levels in their blood than bull sharks caught in salt water.

A bull shark copes with fresh water by lowering the urea in its tissues. In fresh water, its kidneys work hard to keep salt in its body. Bull sharks can live in water as salty as 53 parts per thousand, which is saltier than ordinary sea water. Young bull sharks enter estuaries and lagoons with low salt as easily as adults do.

A bull shark can detect sounds best between 400 and 600 hertz, and can hear sounds from 100 to 1,500 hertz. Bull sharks have small eyes compared with most other sharks in their family. A bull shark's upper teeth are triangles with jagged edges.

Bony fishes and small sharks make up the vast majority of a bull shark's diet. One study of bull sharks found they commonly eat catfish of the family Ariidae. Bull sharks are opportunistic hunters that eat many different kinds of prey, and a bull shark usually hunts alone.

Young bull sharks often grow up in river mouths and bays, where the water is not very salty. The mother carries her pups for 10 to 11 months, and each pup is born able to swim on its own.

Words to know

• hertz: sound cycles
• estuaries: river mouths
• lagoons: shallow salt ponds