Bull shark: everything you need to know about this incredible animal

Bull shark diving is an increasingly popular activity in Playa del Carmen, with people coming from all over the world to admire it in its natural habitat. In Aquaworld we believe that, in order to fully appreciate it and in a safer way, it is essential to know some useful bull shark facts and characteristics.

In this article, we will answer the most frequently asked questions about this misunderstood giant of the seas, and I will also tell you a little about the fun facts that set it apart from any other species of shark.

Did you know there’s more than one bull shark?

First of all, it is necessary to clarify that the animal that most of us know as bull shark (scientific name: Carcharhinus Leucas) is also called Sardinian sharkZambezi shark or lamia shark, and should not be confused with the Carcharias Taurus – known as sand tiger shark or damsel shark.

This confusion is quite normal due to the fact that the damsel shark has the Latin word ‘taurus’ in its scientific name, which literally translates to “bull”. Obviously this poses no difference in the experience of diving with the bull shark, but it is good that you have in mind that there are two sharks with this name, which have nothing in common (in fact, the last common ancestor of these two species existed 140 million years ago, so we could not even call them “cousins”).

carcharias taurus and carcharhinus leucasLeft: Carcharias taurus           Right: Carcharhinus leucas

What is a bull shark like?

Like all shark species, the bull shark is incredibly agile in the water, reaching speeds of up to 25mph (by comparison, Olympic champion Michael Phelps reaches a top speed of 6mph). Wondering how big is a bull shark? The bull shark size reaches a maximum length of 11 ft and, depending on its age, weighs between 198 and 570 lbs.

The appearance of bull sharks lives up to their name, since, with their short, wide snout and chubby body, they could be considered the “bulls of the sea”. They have long pectoral fins and saw teeth. The upper part of their body is grey with a green-brown hue and their belly is white; if you notice dark spots on their fins, you will know that you are seeing a young specimen because these spots disappear as they grow.

four adult bull sharks swimming

A very interesting fact about bull sharks (both female and male) is that the bull shark testosterone levels are believed to be one of the highest in the animal kingdom, even higher than those of a male African elephant in heat! Of course, this would explain why they are so territorial and one of the most aggressive shark species, however, more studies need to be done to confirm anything.

If their large size and reputation as one of the “meanest” animals doesn’t seem like reason enough to respect them, another impressive fact is that, despite not being anywhere near the biggest animals in the sea (that title is taken by the whale shark), the bull shark bite is the most powerful, with 1349 lbs of strength for an adult specimen.

One of the bull shark’s main characteristics, which differentiates it from all other types of sharks, is its unusual ability to adapt its organism to freshwater. Yes, this incredible animal evolved in such a way that its kidneys, liver and rectal gland can gradually adjust to the salinity of the water in which they are found. When they change environment, their kidneys remove less salt and more urea from the bloodstream through urine, allowing them to move where no other shark species can. (If that’s not adaptation and evolutionary perfection, I don’t know what it is.)

Where does the bull shark live?

The bull shark can be found roaming the shallow, warm waters of all the world’s oceans, particularly the tropical coasts.

global bull shark distribution map

Thanks to its amazing ability to adapt, this shark is one of the few species (and the only one in the Americas) that can remain in freshwater bodies for about a year or more. In fact, they travel long distances in freshwater, which is why it’s not weird to find the bull shark in rivers and lakes. In Africa, they can be found in the Zambezi River (hence their name, Zambezi shark); in America, they have been seen in Lake Nicaragua, Lake Maracaibo, and in the Amazon and Mississippi rivers.

Even today, the scientific community does not know the reasons why this species moves to freshwater. There are several theories, such as that these specimens travel to freshwater to get rid of parasites that live only in saltwater or that they do so as a way of ingesting other nutrients that do not exist in the sea; however, nothing has been confirmed.

The case of Lake Cocibolca

A funny anecdote, which I find worthy of sharing, is that in 1877 a group of scientists studied a mysterious species of freshwater shark found in Lake Cocibolca – better known today as Lake Nicaragua. They concluded that it was a rare species of freshwater shark, endemic to that lake. A popular hypothesis claimed that Lake Nicaragua must have started out as a bay in the Pacific Ocean that closed up as time went by, trapping some sharks inside that evolved into a brand new species—the so-called “Lake Nicaragua shark,” which ichthyologists called Carcharhinus nicaraguensis. The Nicaraguan government was so proud that they issued a special edition of stamps with the image of the shark as a symbol of national identity.

two nicaragua postage stamps with the image of a bull shark

It was not until 1976 that other researchers realized that the species in question was the bull shark, which still today travels 200 kilometers along the San Juan River, from the Caribbean Sea to Lake Nicaragua. Unfortunately, far fewer specimens are now found in the area, due to indiscriminate fishing by locals.

How does the bull shark reproduce?

How are you doing so far? I hope you are enjoying as I am learning about these animals, which are true evolutionary wonders. Now let’s talk about how the bull shark reproduces.

Bull sharks can reproduce at any time of the year and are viviparous, so they give birth to live, fully developed offspring, just like us! Inside their shark mother’s womb, the young feed on the yolk sac (inside the placenta), which provides the young with all the necessary nutrients.

Even so, these sharks are so intense that competition for life begins even before they are born; it has been proven that intrauterine cannibalism occurs during gestation. As you can hear, the strongest and most developed offspring also feed on their littermates, even inside the womb! This is really not due to their “intensity” (that was a joke), but to an evolutionary behavior that ensures that only the best-prepared individuals are born.

When giving birth, the female produces up to 13 embryos per litter, measuring between 56 and 81 cm. Newborns are euryhaline, i.e. they are able to live in waters with a wide range of salt concentrations (e.g. in a river upstream and near the mouth) without their metabolism being affected. This makes perfect sense if you consider that these sharks give birth in estuaries and rivers, where the young can grow up protected from other predators to a larger size and go out to sea.

What do bull sharks eat?

Trying to list all the things the bull shark eats would be a never-ending tale, because these sharks eat practically everything: many species of fish and mollusks, of course, but also various types of sea turtles, birds, different types of dolphins and even other elasmobranchs (smaller rays and sharks)…practically everything you can find.

bull shark eating a tuna

What is definitely not in its food chain naturally is us, humans, despite holding the title of “the most dangerous shark for humans”. This idea of the bull shark is to some extent true, but not because they are a human killing machine as some people think (I repeat, humans are not part of their usual diet, nor are they interested in us). Its reputation is due rather to the fact that circumstances are given for there to be these accidents.

Think about it, we already talked about these sharks living mainly in tropical and shallow coasts, frequenting the fresh and turbid waters of estuaries. What areas do we humans visit most? Precisely the ones inhabited by the bull shark. Unfortunately, this gives rise to many incidents in which the Sardinian shark bites people by accident (confusing them with one of its usual prey) or out of curiosity.

Although it is indisputable that the bull shark is among the three species of sharks most likely to attack humans – along with the great white shark and the tiger shark – the truth is that the panic they are in is disproportionate; between 1580 and today, there have only been a total of 100 confirmed bull shark attacks on humans. Sadly, we cannot say the same about human attacks on sharks.

Bull shark diving Playa del Carmen

bull shark and scuba diver in playa del carmen

Appreciating these magnificent sharks alive and in their habitat is a real privilege that we can enjoy in Playa del Carmen, Mexico. The characteristics of the Riviera Maya make it one of the best places to dive with bull sharks, not only in Mexico but worldwide.

The best time to dive with bull sharks is from November to March when groups of pregnant females take advantage of the warm water and approach the coast to give birth to their pups. It is believed that their goal is to reach the freshwater outlets of the cenotes systems, which are protected by mangroves, offering an ideal place for their offspring to grow.

The experience of being underwater, surrounded by approximately 15 pregnant female bull sharks is a dream for most divers, and with Aquaworld you can make it happen! This is the kind of adventure that is worth living and whose memory is with you forever.

bull shark and scuba divers in playa del carmen

Of course, due to the complexity of this dive, the experience is not open to everyone. To be eligible, you must be a certified diver (minimum Open Water certification), with at least 20 logged dives and have dived in the last two years. In case more time has passed since your last dive, you can take a test dive earlier to refresh your skills.

The important thing is that you feel comfortable and safe with your diving knowledge so that for approximately 40 minutes you can fully enjoy seeing these wonderful animals in their own world.

Although the bull shark is not currently an endangered species, its mere presence in waters more accessible to humans makes it vulnerable to fishing and the environmental changes associated with habitat modification. Sadly, its fins are the main product driving demand for this and many other species. With activities like this, we hope to spread and raise awareness about how wonderful and valuable the bull shark is.

Are you ready to swim with this majestic wonder of evolution?

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