The bull shark's ability to live in rivers rests on how it handles salt, and researchers have studied it in several ways. A bull shark can adjust the salt and water balance in its body, and its gills, rectal gland, blood, hormones and kidneys all play a part. In a laboratory study, young bull sharks moved from fresh water into sea water tolerated rapid and big increases in salinity by quickly raising the concentration of their blood, and in that same study the move from 75 percent sea water to full sea water was a greater challenge to the sharks' salt balance than the move to the weaker mix. Separately, 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, and in fresh water its kidneys work hard to keep salt in its body.

Young bull sharks need a place to grow, and recent studies describe where they find one. In a 2024 study of coastal sharks, young bull sharks used the freshwater-influenced upper reaches of bays and estuaries as nursery habitats and moved toward marine places as they grew. A tracking study of young bull sharks found that their home-range sizes were consistent through time, and in that tracking study individuals used the entire monitored section of the river. Young bull sharks enter estuaries and lagoons with low salt as easily as adults do.

Studies of what bull sharks eat also give a wide picture. Bull sharks are opportunistic hunters that eat many different kinds of prey, and 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. In a 2024 study, bull sharks were described as dietary generalists that feed on a wide range of prey, and in another 2024 study bull sharks had the widest range of food sources of the three coastal sharks compared, as measured by isotopes in their bodies.

Numbers about the jaws need care, because they are calculated. In a 2024 study, a bull shark's theoretical bite force ranged from 70 to 1,297 newtons, with notable increases at about 75 to 80 centimetres of fork length, and the study said that bite force scaled with significant positive allometry, meaning it grew faster than body size would predict. In a study of bite force, the calculated bite force at the front of the jaws ranged from 36 to 2,128 newtons, and the bite force of immature bull sharks also scaled with positive allometry. In a study that calculated bite force, the largest bull sharks had a calculated bite force of up to 5,914 newtons at the back of the jaws.

Where do bull sharks spend their lives, and how safe is that place? A satellite-tag study reported that bull sharks are found mostly in shallow water and tend to stay in the same place for long periods, and it said its results show the importance of the coastal zone to bull sharks. Because bull sharks use estuaries and fresh water, they are more exposed to harm from people, and their nursery waters near shore are at risk. Bull sharks are caught in fisheries around the world, though they are rarely the kind of fish the fishers are after. As of November 2026, the IUCN Red List rates the bull shark as Vulnerable, and its numbers are going down, and a wildlife group lists the main threats as fishing, habitat damage and climate change.

Words to know

• nursery: pup-raising place
• newtons: force units
• allometry: growth with size