Bull shark

Scientific name

Carcharhinus leucas

Family

Carcharhinidae

Size

4 m (12 ft)

Lifespan

32 years

About Bull sharks

The bull shark is the most well-known of the shark species that can move easily between salt and freshwater habitats. Their freshwater tolerance puts the bull shark at a distinct advantage over other shark species, as they can use low-salinity areas to both increase their hunting range, and as a protection for their young. In some areas, fresh and brackish coastal waters are used by bull sharks as nursery grounds where juveniles can grow and feed with a lower risk of predation by other species of large sharks. As adults, bull sharks mostly occupy shallow, coastal waters, and undergo seasonal migrations similar to other coastal species, likely for reproduction and feeding, and many occupy coral reef habitats in tropical seas. 

Sharks are ‘osmoconformers’, meaning that they actively regulate their internal salinity to match their environment. The extra salt they take on is concentrated by the kidneys and excreted using a special salt gland. For species that travel between fresh and saltwater, the amount of salt excreted is adjusted to maintain their osmotic balance, though it is energetically costly and the sharks are more susceptible to stress in freshwater.

Diet

Bull sharks have relatively small eyes and often live in murky water, so they often use other senses to find prey. They mostly feed on bony fishes, but are also known to prey upon turtles, rays, and other small sharks.

Distribution

Bull sharks are found worldwide in tropical to subtropical coastal waters, including several river systems and some freshwater lakes.

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