Great whites are the flashy man-eaters of the silver screen. Tiger sharks have a cool nickname. Among the three species of shark that are known to most commonly attack humans, the bull shark gets the least amount of press. What you may not know is the bull shark could actually be the most dangerous of them all. Why? Because it swims where humans do -- close to shore.
The bull shark goes by many different names. Its scientific designation is Carcharhinus leucas. Depending on where you are in the world, you might also hear it referred to as a Ganges shark, Zambezi shark, ground shark, shovelnose, freshwater whaler, swan river whaler or slipway grey.
By any name, bull sharks can be found in warm waters all over the world. They've been spotted as far north in the Atlantic as coastal Massachusetts and as far south as Brazil. In the Indian Ocean, you can find them from Africa and India to Vietnam and Australia. They tend to avoid the cold waters of the Pacific, though they have been seen from Baja, Calif., down to Ecuador.
What's interesting about the bull shark is that it's not just found in the ocean. It's one of only two species of shark that can live in freshwater -- the other is the rare river shark. Bulls are commonly seen in rivers and lakes, and not just in tidal creeks -- these guys really get around. They've been reported 2,200 miles (3,700 km) upstream the Amazon River and as far up the Mississippi River as Illinois.
The International Shark Attack File (ISAF) places the bull shark third on the list of unprovoked attacks on humans, with 77 incidences and 25 fatalities as of April 2008. The tiger shark comes in at second with 88 attacks, but both of these totals are dwarfed by the great white, which clocks in at 237 unprovoked attacks [source: ISAF]. However, shark experts believe that many bull shark attacks may go unreported in the waters of the Third World countries it often navigates.
In this article, we'll teach you all you ever wanted to know about bull sharks. What they look like, what they eat, where they eat, how they reproduce and how they're able to survive in freshwater -- not to mention what makes them so deadly.
Bull sharks got their name for a reason. For one, their body is shorter and more stout than that of their famous cousin, the great white. They also have a blunt, rounded nose that's wider than it is long, giving them a bullish appearance. The name might also come from their aggressive demeanor.
You can tell bulls apart from other species of shark by their lack of an interdorsal ridge. You know the large fin on a shark's back that sticks out of the water and scares the daylights out of ocean swimmers? That's called the dorsal fin. The bull shark has a second dorsal fin farther back and much smaller than the first. The area between the two dorsal fins can either be flat, or have a small, raised ridge of skin -- this is the interdorsal ridge. The fins of a young bull shark typically have dark tips, but they grow out of this awkward stage in adulthood.
Bulls are dark to light gray with a white underbelly and have smaller eyes than many of their shark cousins. Their small eyes indicate that they have limited vision, which could account for the fact that they like to swim in murky waters near the shoreline where eyesight isn't as important and prey is abundant. Their jaw is stuffed with hundreds of wide, triangular teeth that are about 1.5 inches long, heavily serrated and perfect for tearing apart the flesh of their prey.
Aside from being wider than great whites and having a rounder nose, bulls are also shorter. A large great white can grow up to 20 feet (6 m) long, but a full-grown adult bull shark is usually no more than 11 feet (3.3 m) long, topping the scales at about 500 pounds (226 kg). This is the largest they'll ever get, though. A typical female, which grows larger than the male, is about 7.8 feet (2.3 m) and weighs around 285 pounds (129 kg). The male only grows to about 7.3 feet (2.2 m) and weighs a paltry 210 pounds (95 kg) on average. Why are the females larger? Simply because they live about four years longer and continue to grow throughout their lifespan.