Bull shark (Carcharhinus leucas)

Physical characteristics

Bull sharks have a broad, flat snout, strong body and relatively small eyes compared with some other sharks. Their coloration is typically grey on the back and sides with a paler underside. Adults commonly measure around two to three metres in length, with larger specimens reported. They are powerful swimmers and opportunistic predators, using speed and strength rather than stealth.

Habitat and physiology

Unlike most marine sharks, bull sharks can survive in both salt and fresh water by adjusting internal salt balance through specialized kidneys and a rectal gland. This ability allows them to move into estuaries and freshwater systems; such movements are often seasonal or linked to feeding and breeding. Their range includes tropical and subtropical coastal waters worldwide as well as many riverine systems.

Diet and behaviour

Bull sharks are generalist predators. Their diet consists mainly of fish, rays and small sharks, and they will consume crustaceans, birds or mammals when available. They are often described as assertive and sometimes aggressive, a reputation that stems from their presence in shallow coastal waters where people swim. Globally, they are frequently listed among the species most often implicated in unprovoked shark bites.

Reproduction and lifecycle

Reproduction in bull sharks is viviparous: females give birth to live young after an extended gestation. Pregnant females commonly use estuaries or river mouths as nursery areas where pups can grow with reduced predation pressure. Juveniles remain in inshore or freshwater habitats until they are large enough to move into deeper coastal waters.

Conservation and human interactions

The International Union for Conservation of Nature (IUCN) currently lists the bull shark as Near Threatened. Populations face pressure from coastal fishing, bycatch and habitat degradation, including pollution and loss of nursery habitats. Because bull sharks frequent shallow waters used by humans, they are central to discussions about beach safety and shark conservation.

Quick facts

• Scientific name: Carcharhinus leucas.
• Typical habitat: coastal tropical/subtropical waters and inland rivers (estuaries, river systems).
• Notable ability: osmoregulatory tolerance for fresh water (physiology).
• Conservation status: Near Threatened (IUCN), affected by fishing and habitat loss (conservation).

Because bull sharks bridge marine and freshwater environments, they are of particular interest to scientists, conservationists and coastal communities. Understanding their biology and movements helps inform management measures that balance human safety with species protection.