In the shallow waters close to shore, a dangerous predator lurks. With its blunt snout and aggressive nature, the bull shark poses a greater threat to humans than almost any other shark in the ocean.
The only reason it’s less feared than the great white is that it’s more difficult to identify.
The bull shark lives a largely solitary, secretive life in shallow, murky waters where its environment provides the perfect camouflage.
Dangerous though it is, the bull shark is also fascinating. It’s one of the only shark species to survive comfortably in fresh water and can travel as far as 1750 km inland.
Because its habitat includes the shallow ocean waters and rivers that humans most commonly utilize, we’re more likely to come into contact with a bull shark than almost any other species.
They say it’s better the devil you know, so you’d better keep reading and find out everything you can about the bull shark… just in case!
What do Bull Sharks Look Like?
The bull shark has a short, blunt snout that resembles that of a bull, hence its name. It’s comparatively wider and bulkier than a lot of sharks, giving it a more rounded appearance.
Bull sharks have the same countershading as the great whites, with the dorsal side of their bodies being a dark grey and their underbellies pure white.
This countershading provides effective camouflage in their watery world.
Bull sharks have long pectoral fins, the tips of which are dark and particularly distinctive on young male sharks.
Smaller than the average great white, the average bull shark measures between 7 and 11.5 feet in length and weighs around 200 to 500 pounds.
In 2012, marine ecologist Neil Hammerschlag caught and released what’s believed to have been the largest bull shark on record.
Nicknamed Big Bull, this female shark was 10 feet long and weighed around 1,000 lb. According to Hammerschlag, it wasn’t so much the length but the girth that astounded him.
“It had this neck that was just bulging, like a wrestler,” he said.
Bull Shark Taxonomy
Like all sharks, the bull shark belongs to the subclass Elasmobranchii. along with all other cartilaginous fish.
Like the other members of this subclass, it has 5 pairs of gill slits, a rigid dorsal fin, and no swim bladder to help with buoyancy.
As a type of requiem shark, it belongs to the genus Carcharhinus, along with 28 other species. These sharks are thought to have gotten their name from the old French verb, “reschignier” which means “to grimace while bearing teeth.”
All requiem sharks have round eyes with nictating membranes, or third eyelids, that protect their eyes.
They also have rounded snouts and, for the most part, lack spiracles which are straw-like openings that many bottom-dwelling sharks use to ventilate the gills while at rest.
The bull shark’s teeth are also typical of other sharks belonging to the Carcharhinus genus. In the upper jaw, the bull shark has broad, triangular teeth that are heavily serrated.
The lower jaw features narrow, needle-like teeth specifically designed “for grasping slippery meals.”
At first glance, the bull shark closely resembles other members of the requiem genus, including various reef sharks that utilize a similar habitat.
However, bull sharks are more muscular and have bigger heads, but you’re probably not going to hang around long enough to find that out!
The scientific name for the bull shark is Carcharhinus leucas, but this species goes by several other names, including Zambezi shark, Lake Nicaragua shark, River shark, Estuary Whaler, and Freshwater Whaler.
Bull Shark Characteristics
Like most requiem sharks, bull sharks rely on ram ventilation to breathe, which means they need to keep swimming to get the oxygen from the water into their lungs.
One huge difference between bull sharks and other requiem sharks is their ability to live in freshwater just as effectively as it does in salt water.
Bull sharks are euryhaline, which means they can tolerate different salinity levels. The bull shark is so adept at this that it is one of the only shark species that enters freshwater river systems and thrives in them.
Unfortunately, the bull shark’s ability to tolerate brackish waters brings it into the same environments frequented by humans.
River mouths and shallow coastal waters are some of the bull shark’s favorite hang-outs, and it doesn’t welcome visitors!
The bull shark is considered one of the most aggressive and dangerous shark species out there, but it’s also got the greatest bite force, pound-for-pound, of any known shark.
With a bite force of 6,000 Newtons, or 1,350psi, the bull shark can break bones and smash its way through turtle shells. According to some scientists, it’s far “greater than what is required to kill and eat prey.”
Bull Shark Life Cycle
Like other requiem sharks, bull sharks are viviparous, giving birth to live young. The pups are born after a 10 to 11-month gestation period, during which time a yolk-sac placenta nourishes them.
At the end of the gestation period, the female bull shark gives birth to a litter of between 1 to 13 young.
Bull shark pups measure between 55-85cm long at birth and are born free-swimming, autonomous, and ready to hunt.
The female abandons her pups the moment they’re born, leaving them to fight for their survival in coastal nursery habitats. These are usually located in freshwater systems that protect them against other adult sharks.
Juveniles remain in their nurseries until around four years of age when, as subadults, they venture into warm, coastal habitats.
Male bull sharks become sexually mature at around 14 to 15 old whereas females take nearly 18 years, by which time they’re approximately 6 to 7.5 feet long.
Bull sharks usually mate in late summer or early autumn, selecting near-shore bays and estuaries for their courtship. While we know they mate via internal fertilization, we have few details regarding the specifics of this event.
Living for around 20 to 30 years, bull sharks have a considerably shorter life expectancy than other shark species, including the great white which can live to over 70.
Where do Bull Sharks Live?
Bull sharks are found worldwide in shallow, coastal waters and freshwater systems. In the US, bull sharks are found in the Gulf of Mexico and all along the East Coast.
The bull shark’s ability to tolerate low salinity also means it’s free to travel into rivers and other freshwater systems globally.
Bull sharks have been spotted in the Amazon and Missippi Rivers, and there is a significant population of between “1,000 and 3,000” bull sharks living in Australia’s Brisbane River.
Lake Nicaragua was once famous for its freshwater sharks, but scientists now fear that population has been largely destroyed by “a shark-fin processing plant along the San Juan river.”
Bull sharks prefer shallow waters, with most residing and hunting in water less than 100 feet deep.
Like many sharks, bull sharks migrate seasonally, traveling north during the summer and returning to warmer, southern waters again in winter.
Not only do bull sharks like coastal waters, but they also enjoy brackish, murky environments like those found at river mouths and estuaries. Juveniles also spend time in nursery habitats such as salt marshes and mangrove forests.
Bull Shark Behavior
The bull shark gets its name partly from its blunt snout and partly from its tendency to headbutt its prey before attacking it.
It’s believed this behavior enables the bull shark to identify its prey in murky waters where visibility is poor.
Bull sharks are highly territorial, which is why they appear so aggressive towards humans. If you enter a bull shark’s territory, he’s liable to respond to your intrusion with a violent attack.
It’s believed that bull sharks were responsible for a spate of attacks off the coast of New Jersey back in 1916. The incident is said to have inspired Peter Benchley to write his bestselling novel, Jaws.
Bull sharks are generally solitary animals that use a combination of speed, agility, and aggression when hunting.
Although not the fastest shark in our oceans, bull sharks can reach a top speed of around 40kph, which is considerably faster than a human with an average swimming speed of just over 3kph.
Because the bull shark frequents the same shallow, coastal waters as humans, it’s been implicated in numerous attacks, and some experts consider it to be even more deadly than the great white.
According to the International Shark Attack File, bull sharks have been responsible for 119 attacks on humans, of which 26 have proved fatal.
A couple of weeks before writing this, a woman was killed by a bull shark while snorkeling in the Bahamas, taking that total even higher.
What do Bull Sharks Eat?
Bull sharks aren’t particularly fussy about their diets, eating almost anything that comes their way.
Although adult bull sharks eat mainly bony fishes and other small sharks, they’ll also gobble up the occasional stingray, turtle, or dolphin. They’ve even been known to eat seabirds and dogs!
As juveniles, bull sharks are heavily dependent on the fish species specific to their nursery grounds, namely mangrove forests and salt marshes.
A recent study of the juvenile bull shark’s nutritional dependency on estuarine habitats found that the salt marsh is the primary producer for young sharks. It supports “a range of organisms, such as crustaceans, elasmobranchs, and teleost fish, which are then preyed on by juvenile bull sharks.”
In the Western Atlantic, bull sharks primarily prey on schooling fish such as catfish, mullet, mackerel, and snook. In South Africa, their favorite foods include oysters, small fish, and turtles. They’ve even been known to take down baby hippos when given the opportunity!
What Hunts Bull Sharks?
Adult bull sharks have very little to fear. Few predators are brave enough to tackle 500 pounds of pure aggression!
For juveniles, however, it’s a different story. Not only do they need to avoid predation by adult bull sharks, but they also from the threats posed by tiger and sandbar sharks.
They aren’t the only ones willing to make a meal out of a careless bull shark either. Crocodiles have been photographed killing and eating bull sharks on two separate occasions.
The first incident occurred in Australia in 2014, when a large, 18-foot crocodile, Brutus, took down a bull shark in the Adelaide River.
A similar scenario was filmed off the east coast of South Africa last year when another large crocodile killed a bull shark before swallowing it whole.
Commercial fishing has little impact on the coastal bull sharks, although some smaller fishing operations target them for their fins and oil.
The IUCN lists the bull shark as near threatened, which the National Wildlife Federation says is primarily because their preference for coastal waters places them “more at risk from pollution and habitat degradation than other species.”
The bull shark is agile, muscular, and aggressive. It might not be as big as a great white, but its belligerent attitude makes it even more dangerous.
Not only is the bull shark territorial, but the territory its protecting is situated just offshore, in precisely the same zone as humans choose to swim and snorkel.
Unsurprisingly, the bull shark is responsible for more than just a handful of attacks against humans, some of them fatal.
Before we give the bull shark a bad name, let’s be clear about one thing. Humans aren’t on the menu. The only time bull sharks attack humans is when they mistake them for their usual prey species.
While bull sharks are undeniably dangerous, losing this near-threatened species would be would even more alarming.
Bull sharks are apex predators in their habitat and, as such, have a critical role to play in shaping their “marine communities through predation and associated risk effects.”
Without bull sharks, the entire coastal ecosystem would be off-balance, so while we might not want to meet one, we should learn to respect their presence.
Nicky is a British adventurer and animal lover who spends her time exploring the natural world and writing about her experiences. Whether on horseback, underwater, running, hiking or just standing with a fishing rod in hand, she embraces everything her adopted home of South Africa has to offer.