Bull sharks are so named because their thick, stout body and short, blunt snout give them the appearance of a bull. They’re also rather aggressive and bull-headed, and they like to bully their prey with head butts before they eat it.
Bull sharks are medium-sized sharks that can grow up to 11 feet long and weigh about 700 pounds, although females generally top out at 5 feet and males usually reach 7 feet in length. They’re gray on top and white on bottom so that they’re camouflaged against the dark depths when prey is above them, and they blend in to the lighter surface when prey is below them.
Bull sharks are pretty fascinating creatures, as you’re about to see.
1. Bull sharks have lots and lots of teeth
All sharks have jaws that are filled with sharp, serrated teeth. The teeth are in rows that act like conveyor belts. When one tooth is lost, the tooth behind it moves forward, sometimes as quickly as within a day, to replace the lost one. A shark may lose and re-grow more than 20,000 teeth over the course of its lifetime!
The average number of rows of teeth in a shark’s jaw is 15, but the bull shark isn’t your average shark. It’s certainly not a bull you want to run with: The bull shark has around 50 rows of teeth in its jaws, and each row has about 7 teeth, for a grand total of around 350 teeth in its mouth at any given time.
2. Bull sharks enjoy fresh water as much as salt water
Sharks have to have salt in their body for survival. When excess accumulations of salt build up in the body, a rectal gland excretes the excess. The rectal gland of the bull shark is less active than that of other sharks, which makes them able to live in fresh water. When their body needs more salt, the liver gets to work producing urea, which allows them to adapt to any change in salinity.
Bull sharks have been known to inhabit rivers and freshwater lakes. In fact, a bull shark was spotted in Illinois after swimming up the Mississippi River, and another swam 2,000 miles up the Amazon River in Peru.
In Queensland, Australia, there’s a golf course with a large freshwater lake that’s home to a school of bull sharks who were trapped there after a flood in the ’90s. The golf course is popular among local golfers for the monthly tournament called the “Shark Lake Challenge.”
3. Bull sharks give birth to live young
Sharks give birth in one of three ways. If they’re oviparous, they lay a sac full of eggs (called a “mermaid’s purse”), which attaches itself to a rock or other surface until the eggs are ready to hatch. If they’re viviparous, they gestate live shark pups and then give birth to them live. If they’re ovoviviparous, they develop eggs, which hatch in the womb. The newly hatched sharks are birthed live.
Bull sharks are viviparous, and a female shark will have between four and 10 sharks per litter. The gestation period for bull sharks is 12 months, after which they give birth in fresh water because the pups are born with a low tolerance for salinity. Bull shark pups are about two feet long when they’re born, and once they develop a little, they swim out to sea.
Bull sharks have a lifespan of about 12 years in the wild.
4. Bull sharks are considered by many experts to be the most dangerous shark
Tiger sharks and great white sharks join the bull shark as the Trinity of Terror, the three sharks identified as the most frequent attackers of humans. In fact, the bull shark was likely responsible for the 1919 attacks that inspired the movie Jaws, which increased the number of cases of severe galeophobia, or the fear of sharks, from a handful to a nation full.
Bull sharks like warm waters near the shore, much like humans. They’re common, and aggressive, also like humans, and they’re agile and pretty fast, reaching speeds of up to 12 miles per hour. But much like the great white shark, bull sharks rarely actually eat humans, but rather bump ‘n’ bite ’em out of curiosity. Once they get a nibble, they roll their eyes in indignation and swim off to find something edible. (The tiger shark, on the other hand, will eat just about anything.)
Unfortunately for those humans who are “tasted,” the bull shark has the highest bite force among all sharks, so that little nibble comes at a force of 1,300 pounds per foot.
5. But humans are more dangerous to the bull shark than the bull shark is to humans
Bull sharks are classified as “near endangered” on the IUCN’s Red List. Although bull sharks are very commonly seen by humans due to their habitat, their numbers are dwindling due to over-fishing of sharks in general, and particularly sharks that are easy to catch or trap, such as those that live in shallow waters near shore.
Bull sharks and other species are killed for their fins, liver oils, and skin. The fins are used for the Asian delicacy shark fin soup, and the liver oil finds its way into cosmetics and vitamins. The skin is used for accessories like sharkskin belts and boots. But is a bowl of fin soup or a smooth lipstick worth devastating entire shark species? Some seem to think so.
But the fact is, scientists very recently estimated that humans kill an astonishing 100 to 273 million sharks every year. If we split the change and call it 200 million sharks, that adds up to 380 sharks killed every minute of every day. In the time it takes you to say the word “shark!” six sharks have been killed.
Compare those numbers to the 16 people who are attacked by sharks every year and the one person who dies from a shark attack every two years, and it’s easy to see who’s really the most dangerous predator in the ocean.