The Bull shark (Carcharhinus leucas) is a requiem shark from the family Carcharhinidae and order Charcharhiniformes. This shark is most common in warm shallow waters along the coast throughout the world.
An interesting fact about the Bull shark is that not only does it swim to brackish waters, it also survives in freshwater. Thus, occasionally found in shallow brackish and freshwater environments which include rivers and estuaries.
A common name for this shark in Africa is “Zambezi River shark”, or simply “Zambi”. Similarly, in Nicaragua, this shark is commonly identified as ” Lake Nicaragua shark”.
Bull sharks are not true freshwater sharks as is the case of shark in the genus Glyphis. However, they can swim far up rivers miles away from the ocean. For instance, this shark notably travels up the River Mississippi as afar as Alton, Illinois. Whereby, this distance is about 700 miles (1100 km) from the ocean.
Learning about Bull sharks is very important because it is among the most aggressive and most likely shark to attack humans. As such, larger sizes of this shark species are probably responsible for most near-shore shark attacks. There are speculations of them involved in some attacks blamed on other shark species.
History of the name Bull Shark
Bull sharks got their common name from the shark’s broad and stocky body shape, their flat snout coupled with their unpredictable and very aggressive behavior.
Apart from the common name Zambezi River shark and Lake Nicaragua shark, the Bull shark in India may be misrepresented as Sundarbans or Ganges shark. And, referred to as such in that locality. There are also other local names of the Bull shark resulting from the shark’s diverse habitat.
Bull Shark Identification
If by chance you see a shark in any freshwater, it is likely to be the Bull shark. Of course, there are true freshwater sharks of the genus Glyphis with three species. However, these sharks are quite rare. But, this is not enough.
Bull sharks are large sharks that usually grow to an average length of about 7.4 feet (2.25 m) to 7.9 feet (2.4 m). Where the female bull shark grows larger than the males, they will take the higher side of the range and the males keep toward the lower side.
This shark species can grow extensively large with common reports of about 11 feet (3.5 m) in length. They have a stocky body shape, as such are wider and heavier than the other species of requiem sharks of comparable size.
Bull sharks have a gray color on top of their body, while underneath is a white color.
The caudal fin of the Bull shark is longer and lower when compared to that of larger sharks. Also, its first dorsal fin is larger than the second. The pectoral fins are long. And, the fins have black tips especially noticeable in young Bull sharks.
The snout of Bull sharks lacks an inter-dorsal ridge and not very large. They have triangular teeth with a very strong bite force. In fact, their bite force is the greatest among already measured cartilaginous fish species with a force of up to 6000 newtons.
The female bull shark has an average weight of 290 lb (130 kg). Meanwhile, the smaller males on maturity may weigh just about 209 lb (95 kg)
Distribution Range and Habitat
The Bull shark is extant worldwide across the coast of warm oceans. Also, found in freshwaters such as rivers, lakes, and occasional streams. This shark would swim within a depth of 490 feet (150 m). However, they prefer to stay in shallow waters, thus, they would not usually go deeper than 100 feet (30 m).
Bull sharks in the Atlantic have a wide distribution from Massachusetts to southern Brazil. Then, from Morocco to Angola. And, in the Pacific Ocean, their distribution mostly occurs from Baja California to Ecuador.
This shark also has large populations in known major rivers. As a result, the record has over 500 bull sharks inhabiting the Brisbane River. Other freshwaters where the Bull shark lives include Lake Nicaragua, the Ganges and Brahmaputra Rivers of West Bengal, Zambezi River, and Assam in Eastern India with adjoining Bangladesh.
On the other hand, Bull sharks also survive in waters with high salt content such as the St. Lucia Estuary in South Africa.
For the fact that bull sharks can survive in wide ranges of water, both marine and freshwater, they do not have limited distribution and are scattered across the globe.
Ecology and Conservation Status
In the wild, Bull sharks have no natural predators, in fact, humans pose their major threat. Although larger sharks such as the great white shark and tiger sharks may attack this species, they typically target the juveniles.
Another known threat of the bull shark is crocodiles which attack the river resident individuals.
In all, the IUCN – International Union for the Conservation of Nature listed Carcharhinus leucas as a “Near Threatened” species.
The threats include deleterious human activities such as increased fishing pressure and habitat degradation. Of course, bull sharks in the water of low salinity are likely to encounter humans than offshore inhabiting sharks.
Often, humans fish bull sharks for commercial purposes, exploiting the shark’s skin, flesh, and liver oil. Even more, the fins currently drive demand for this species and many others.
Another reason for fishing this shark species is recreation. Of course, the bull shark can adapt to tank life, as such exploited by large public aquariums. They are good for public display and represents well a larger, aggressive shark.
The increase in the number of public aquaria worldwide typically means increased demand for the bull shark and other sharks fit for public display.
Typical Bull Shark Behavior
The Bull shark prefers a solitary lifestyle rather than staying in the company of its species. As a result, it would usually hunt all alone.
This shark may not always migrate but can travel to far distances when the need arises. Some individuals from South America travel to the Atlantic Ocean which is thousands of kilometers. Often, they go to brackish or freshwater to birth the young ones.
Their most notable behavior is their ability to effortlessly swim between fresh and saltwater. With this feature, the bull shark can be said to be diadromous.
Bull sharks typically avoid regions with low temperatures. They show the tendency of living near populated areas.
This shark is among the most aggressive ocean sharks. Thus, it has a record of human attacks which is a result of the shark’s frequent swimming to tropical regions where there are shallow, coastal waters. And, humans also stay around these places. Chances are the shark might mistaken humans for a meaty prey, hence the attack.
Bull Sharks Diet
The Bull shark is an active hunter and feeds mainly on small sharks and bony fish. Surprisingly, other bull sharks also make up the diet of this shark.
They can also feed on crustaceans, dolphins, turtles, seabirds, and terrestrial mammals. When hunting, bull sharks attack their prey by first bumping it, then continuously attack it until it is not able to escape. This technique is referred to as the bump-and-bite technique.
Bull sharks prefer to hunt in murky waters. As such, their prey is less likely to see them approaching. Most times, bull sharks will prefer solitary hunting, although they can briefly pair with its species for easier hunting and tricking of prey.
Just like other shark species, the bull shark is an opportunistic feeder. They would normally eat in short bursts and tend to digest food for an extended period during food scarcity to avoid starvation.
Bull sharks can regurgitate food already in their stomach as part of survival adaptation. Thus, they do this to distract their predators to escape. This tactic involves the predator making a move to consume the regurgitated food, then giving the bull shark enough space to escape.
Bull Sharks and Humans Interaction
Bull sharks inhabit shallow waters in many types of habitats, they are aggressive, territorial, and have zero tolerance for provocation. As such, they are most likely to encounter and attack humans.
Bull sharks are among the three most dangerous shark species along with the great white sharks and tiger sharks to attack humans with a good number of recorded attacks. These attacks cuts across fresh and brackish waters in different locations.
On the other side of this interaction is humans fishing and capturing bull sharks for commercial and recreational purposes. Also, there are developmental activities in areas where these sharks are found. All contributing to the decrease in the population of bull sharks.
How Dangerous to Humans is the Bull shark?
There is a belief that bull sharks are responsible for most shallow water shark attacks. However, the ISAF – International Shark Attack File cited the great white shark as the species with the largest number of human attacks. Although the ISAF also noted that while the bite of the great white shark can be clearly identified, it is quite difficult to tell the bite of a bull shark apart from other requiem sharks, that is the members of the Carcharhinidae family. As such, there are speculations that bull sharks are responsible for some human attacks attributed to other species.
In any case, the bull shark is still among the shark species with the highest number of human attacks. More so, they are large, territorial, and aggressive enough to be considered quite dangerous.
The Bull Shark Visual Cues
From studying the bull shark it was found that this shark can distinguish between colors of mesh netting set underwater across its path. Thus, they tend to avoid bright-colored mesh netting rather than those with color blending in with the water.
Bull sharks easily avoided bright yellow mesh netting that is present in their path. And also, bright yellow survival gear attracts this shark rather than the ones with black paint.
This behavior is quite common with sharks as studies show that they can take a visual cue to distinguish between varying objects.
Special Adaptations of the Bull shark
The bull shark has the capability for osmoregulation. As such, they can adjust the osmotic pressure of the body to maintain certain water conditions. Even the closest existing bull shark relatives including the sandbar shark from its genus Carcharhinus are not capable of osmoregulation.
On another note, the bull shark can conserve energy for itself. And, one way it can do this, is by using the tidal flow as it moves downriver during changes in the tidal flow. Thus, their usual downriver movement as young bull sharks have a direct connection to energy conservation according to study.
Also, bull sharks can conserve energy by reducing the energy required for osmoregulation in their surrounding environment. These adaptations help the bull shark to survive in waters of varying salinity. And, ensure the general well-being of the shark.
Mating and Reproduction
Bull sharks will mostly mate in fresh or brackish water during the late summer and early autumn. Their gestation period lasts for 12 months, which after they deliver the young ones alive and free-swimming. The number of pups delivered at a time can range from 1 to 13. And, they measure about 27.6 inches (70 cm) at birth.
While the bull shark is viviparous, they do not rear their young ones. Instead, the deliver them into flat, protected regions. These places include river mouths, coastal lagoons, and other estuaries of low-salinity. They serve as common nursery habitat for bull sharks.
A male bull shark would attain sexual maturity usually at the age of 15 years, while the female would reach 18 years with a size range of 68.9 inches (175 cm) to 92.5 inches (235 cm) before they are able to produce viable eggs for fertilization.
The mature female bull shark may tend to bear scratches and marks resulting from the violent mating ritual. Thus, the male bull shark is likely to bite the female during courting so the female could turn for copulation.
The bull shark pattern of giving birth in freshwater can help to protect the young ones from predators as they grow up. Of course, most other shark species are not able to enter the freshwater and strictly stay in saltwater for survival. Therefore, it is not wrong to say that freshwater serves as a protective area or bull sharks to reproduce because the threats of larger sharks are greatly reduced.
11 Bull Shark Facts to Remember
1. Bull Sharks have a very Powerful Bite
The strength of the bull shark’s bite when measured showed that an adult bull shark can jam its jaws with a force of close to 6000 newtons. And, so far is the highest among other measured sharks and cartilaginous fishes.
2. They Can Survive in Both Fresh and Salt Water
This is the most amazing bull shark fact. Bull sharks are capable of osmoregulation, thus can maintain a balance between the salt and water in their body. They can be found in freshwater and saltwater alike.
3. They Do Well in Public Aquaria
Bull sharks do well in large commercial tanks where they are displayed for recreation. There is a record of bull sharks thriving over 25 years in captivity. The Oklahoma Aquarium in North America houses 10 bull sharks in a tank of about 500,000 gallons. This ability to adapt is rare in sharks of similar temperament.
4. Bull Sharks are among the Shark Species likely to Attack Humans
While it is very rare for a shark-on-human attack to occur, bull sharks are among the shark species implicated for most attacks on humans. As a result, there are over 100 recorded bull shark attacks on humans. Of course, they frequent water areas where humans are found.
5. They have a Territorial and Aggressive Nature
This shark species are extremely territorial and would likely attack anyone that trespasses their zone.
6. Bull Sharks are Solitary Species
The bull shark will tend to stay and hunt alone except during the mating season of late summer and early autumn. Or, on rare occasions where they might pair to track down prey.
7. They are Able to Detect Water Movement Around Them
With their lateral line receptors, bull sharks can detect the movement of water in their surrounding. This helps them during prey hunting.
8. They Do Not Directly Attack their Prey
While hunting, bull sharks will head-butt their prey before attacking them. This usually throws the prey off-balance as they become vulnerable to attack.
9. A Bull Shark Can Regurgitate Food Particles to Distract its Predators
While bull sharks rarely have predators, some larger sharks may attack the juveniles of bull sharks. And to escape, they sometimes regurgitate food which the predator goes to eat while they escape.
10. Mating Involves a Biting Ritual
The male bull shark will bite the female during copulation so they can hang on. This might appear violent, but it is part of the ritual.
11. Carbrook Golf Club, Australia Celebrates the Bull Shark in “Shark Lake Challenge”
This challenge comes after proving the presence of bull sharks in a lake within the golf course. It is believed that the bull sharks were trapped after the flooding of the Logan River next to the course. There are speculations these sharks breed there too.
Can a Bull Shark Make a Good Pet?
The answer is NO! While the bull shark may thrive in public aquaria, it is not suitable for a home aquarium. Thus, this shark species cannot make a pet talk more of a good one.
There is no record yet of a domesticated bull shark. They grow large and require an incredibly large tank. Even if anyone can provide the tank size, bull sharks are quite dangerous, territorial, and aggressive. So, do not think about it!
Bull sharks are not yet endangered, however, they are already near threatened due to fishing pressure. As such, there are speculations that if hunted like this continuously, their population in nature will reduce drastically in years to come.
This shark species do not develop fast and take up to 12 years to mature. Also, they gestate for 12 months to give birth to a range of only 1 to 13 pups. As such, these species require due attention.
- Bull Shark Wikipedia (edited 27 January 2020), Wikipedia. Online here
- Carcharhinus leucas (Bull Shark) IUCN Red List of threatened species. Online here
- Carbrook Golf Club, Australia – Bull Sharks in the Water Hazard Online here
- “Interesting Bull Shark Facts (Carcharhinus leucas)“, ThoughtCo. Online here
- “Bull Shark – Description, Habitat, Image, Diet, and Interesting Facts. Animals.net. Online here