Bull shark

The bull shark is a large, stout-bodied requiem shark that is famous for its euryhaline nature, meaning it can easily survive in both saltwater and freshwater environments. This unique physiological adaptation allows the species to travel incredibly far upriver, with confirmed sightings thousands of miles up the Amazon River in Peru. They have also been found in the Mississippi River as far north as Illinois.

Unlike most sharks, the bull shark possesses specialized rectal glands and kidneys that allow them to retain essential salts and excrete excess water. Through a process called osmoregulation, their bodies automatically adjust their internal concentration to match the surrounding freshwater or saltwater. This allows them to seamlessly transition between the ocean and inland river systems.

Bull sharks frequently utilize shallow, warm freshwater river mouths, estuaries, and coastal lagoons as vital nursery areas for their pups. The murky, low-salinity water provides the young sharks with a safe haven, protecting them from larger marine predators like tiger sharks. The females give birth to live young, typically delivering between 1 and 13 pups per litter.

Yes, the bull shark is widely considered to be one of the three most dangerous shark species to humans, alongside the great white and tiger sharks. Because they prefer shallow, murky coastal waters and river mouths, they frequently come into direct contact with human swimmers and surfers. Their highly aggressive, territorial nature and tendency to bump their prey before biting make them particularly dangerous.