Bull Shark
Carcharhinus leucas
The shark that swims up rivers, thousands of kilometres from the sea.
Most sharks can't survive in fresh water. The bull shark can: it switches its body over to river mode and swims far inland. Bull sharks have been found 4,000 km up the Amazon and far up the Mississippi, and one population lives in a lake — Lake Nicaragua.
On the conservation status
Moved to Vulnerable by the IUCN in 2021. Bull sharks live close to shore and up rivers, right where people fish and build, and females don't have their first pups until they're about 18, so losses are slow to replace.
- Length
- Up to about 4 m (13 ft)
- Weight
- Up to about 315 kg (700 lb)
- Lifespan
- 25 years or more
- Diet
- Fish, stingrays, other sharks, turtles
- Grown up at
- 14–18 years old
- Lives in
- Coasts, rivers and even a lake
The good stuff.
A shark that can live in fresh water
A shark in the sea keeps its blood salty so water doesn't drain out of it. In a river, a bull shark flips that around: it holds on to salt, and its kidneys pump out lots of very watery urine.
Thousands of kilometres inland
Bull sharks have been found 4,000 km up the Amazon, at Iquitos in Peru, and up the Mississippi as far as Illinois.
Built like a bull
It's named for its stocky, heavy body and short, blunt, rounded snout.
Nurseries in rivers
Many bull sharks are born where rivers meet the sea. The water there is less salty and has fewer big predators, and young bull sharks can stay for years while they grow.
Small families
A mother has between 1 and 13 pups, after a pregnancy of about 10 to 11 months.
Slow to grow up
Female bull sharks don't have their first pups until they're about 18 years old, and males aren't grown up until 14 or 15. That's why a population takes so long to recover.
Wait, really?
- ✦
A population of bull sharks lives in Lake Nicaragua, and swims between the lake and the Caribbean along the San Juan River.
- ✦
Every winter, big female bull sharks gather off Playa del Carmen in Mexico.
- ✦
They've been found in the Ganges and Brahmaputra rivers in India, and in the Zambezi in Africa.
What it sounds like
Silent. Sharks have no known calls of any kind.
Where you might see one
Playa del Carmen in Mexico in winter, Beqa Lagoon in Fiji, and Umkomaas in South Africa.
The trouble
- Fishing, both on purpose and by accident
- Pollution and building along rivers and coasts
- Damage to the river mouths where their pups grow up
One real thing
Bull sharks need clean rivers and healthy coasts as much as open sea. Keep rubbish and chemicals out of drains — for a bull shark, the river is home.
More ways to help