It’s been quite a while since I’ve written about a shark, which is a shame, because sharks are awesome. Not all sharks are created equal, however, so I thought end my shark drought by writing about a particularly fearsome species, the bull shark. Bull sharks go by a number of different names, including Zambezi sharks, Nicaragua Sharks, and cub sharks. I’m going to stick with bull shark, for simplicity’s sake.
Bull sharks have a wide range, in tropical and subtropical areas. They are mainly found in coastal areas in the world’s oceans, though they will enter estuaries, deltas, rivers and lakes. In the United Sates, bull sharks have travelled up the Mississippi River as far as Alton, Illinois. Bull sharks don’t like to swim very deep, rarely being found at depths beyond 30 meters.
Bull sharks have earned their name, being large, chunky, and aggressive. Female sharks are bigger than males, reaching average lengths of 2.4 m, with the largest recorded specimen measuring in at a whopping 4.0 m long. Bull sharks have short snouts, and mouths that are filled with large (and terrifying) triangular teeth. There’s good reason to stay away from a bull shark’s mouth: they have the highest bite force of all sharks, relative to body size.
There’s another reason you probably shouldn’t get into water with a bull shark — as mentioned, they are very aggressive. Along with tiger sharks and great whites, bull sharks make up the three most dangerous shark species to humans. Bull sharks are particularly deadly thanks to the wide variety of habitats they live in, as well as their penchant for hanging around in shallow waters. Because people also like to swim in shallow areas, bull sharks run into people more often than other species do. What fun!
Though bull sharks do readily attack humans, they don’t make regular meals out of them. Instead, bull sharks prefer to feed on various fish and small sharks, but will also eat turtles, birds, mammals and stingrays. They have excellent senses of smell and hearing, which they use to navigate the often murky waters they hunt in.
Reproduction in bulls sharks occurs in summer and autumn, when the sharks swim into estuaries and river deltas to mate. Males will often bite female sharks during copulation, leaving nasty scars on their bodies. Female bull sharks give birth to live young, after almost a year’s gestation. Litters range in size from four to ten pups. The young are born in freshwater lagoons, rivers, and estuaries, and stay there until they mature.
Bull sharks are unique among sharks for being able to survive in both salt and freshwater habitats. This gives their young a distinct advantage — the little ones can hang around in the relatively predator-free freshwater areas until they’re big enough to protect themselves. Bull sharks are able to move between salt and freshwater thanks to their kidneys, liver, rectal glands and gills, all which help regulate the salinity of blood in the sharks’ bodies.
Unfortunately, though breeding in fresh, shallow water protects the young sharks from animal predators, these areas are also those that are most affected by human development. In recent years, the number of bull sharks in estuaries has been declining, and the species is now listed as near threatened. I know bull sharks are scary and they attack people, but those attacks are quite rare, and they’re not evil enough to deserve extinction. But do be careful when swimming in shallow waters!
Cover image credit: Pterantula via Wikipedia