Is a Shark a mammal or fish? That is the question that is perhaps most commonly asked when talking about sharks. Since sharks give birth to pups, and a few species lay eggs, the common consensus is that sharks are mammals.
Across the board, though, 70% of all sharks give birth, while the remaining 30% lay eggs. Sharks are actually fish, which is sure to be a surprise to many.
Are Sharks Fish?
Mammals are warn-blooded creatures that are identified by giving birth to live kids, being covered in hair, and feeding their offspring via milk from mammary glands.
Fish are aquatic creatures that are mostly cold-blood. Most have scales, breathe through gills, and come with two sets of fins, some of which are paired, while others are not.
Where do Sharks Fit in to All This?
How do Sharks Breathe?
Mammals and fish are equipped with totally different breathing mechanisms. Sea mammals such as dolphins and whales rely on a blowhole to draw air into their lungs. These mammals periodically need to break the surface of the ocean to draw in that air.
Between those moments, they keep their blowholes closes to prevent water from seeping into their lungs. Fish can stay underwater at all times, using their gills to breathe in and out.
Fish take water in through the mouth and pass it out through the gills. Sharks are not equipped with lungs, but they do have anywhere from 5 to 7 gill openings to help them breathe underwater.
Mammals and fish are also separated by the way in which their skin feels and operates. Warm-blooded mammals have smooth skin that remains that way because their bodies are able to regulate temperature because of that blood flow and temperature.
The skin that covers fish cannot be kept warm that way, and can be adversely affected by the temperature of the water that they are swimming in.
While the skin of a shark may appear to be smooth, it is actually made up of toothy scales known as dermal denticles. These jagged scales prevent the skin from parasitic damage, whilst also helping the shark move through the water quickly.
Read More: Smallest Shark in the World
Sea mammals come equipped with a single dorsal fin, or sometimes none at all. Fish, on the other hand, have more than one dorsal fin, and are usually equipped with several in different parts of the body, with each one serving a specific purpose, such as steering or stabilizing.
The fins that a shark have help them move forward at speed, but are unable to allow them to move backwards or sideways. If a shark want to get past an object, it allows its body to drift away from it.
As you should be beginning to see by now, there are definite looks and traits that clearly identify a shark as a fish.
Sharks come in all different shapes and sizes, with some as small as your hand to others that are upwards of the size of a bus. The Spined Pygmy shark measures in a just 7 inches, while the Whale shark can get up to 50 feet in length.
On average, though, mot sharks fall into the range of human size although roughly 50% of the 368 different types of shark are under 39 inches in length.
The body shapes of sharks are also wide and varied. Most sharks have a torpedo shape that helps them cut through the water quickly. Sharks that fall into the bottom-dwelling variety often have flattened bodies that help them hide along the bottom of the ocean.
Cookiecutter sharks, and some other varieties, have an elongated body, while an elongated snout belongs to the Sawshark.
The wide head of the Hammerhead shark is very different, as it the elongated upper tail fin of the thresher shark.The Goblin shark has an odd-looking protuberance on its head that seems to serve little purpose.
Different Species Of Sharks
Shark species fall into 30 different families and 368 different species. Each family has a distinct look, way of life, and eating habit. They also have different features, personalities, methods of reproduction, and more.
There are species of shark that are quite common, while others, such as the Megamouth, are quite rare. Sharks are part of the Elasmobranchii, which is a group of cartilaginous fish that also includes rays and skates.
Read More: Do Jellyfish Have Brains?
How Many Bones Does a Shark Have?
Sharks have cartilage, not bones, although there are parts of their skeleton that is calcified. Cartilage is strong, but is also softer than bone. To get an idea of how it feels, touch your nose or ears.
How Many Teeth Does a Shark Have?
While sharks can have as many as 3,000 teeth, they do not use them to chew, as they gulp down whatever they eat.
These teeth are arranged in rows, with as many as 5 rows in the mouth at any given time. It is the front set of teeth that does the majority of the work. When a shark loses or damages a tooth, it is quickly replaced by another.
What Do Sharks Eat?
Sharks are carnivores, but what they eat is all over the place.
- Great whites, as well as other varieties, are fast predators that love fish, marine mammals, squid, and even other sharks.
- Slower shark varieties, such as the Angelshark, will crush and eat shellfish that reside on the ocean floor.
- Some sharks operate as filter feeders, gobbling up plankton and small animals, which they do by swimming with an open mouth.
Do Sharks Sleep?
Fish do not sleep in the same way as humans, as they rest by having inactive periods. Some shark types are able to rest on the ocean floor without moving, while others need to be in a constant state of motion to breathe.
When Sharks Attack?
Some sharks, such as the Great White, adopt and aggressive posture prior to attacking. By arching their back and throwing back their head, they put their mouth in a much more favorable biting position. Their tails move more acutely, perhaps because they are preparing for a chase.
While people are sometimes attacked by sharks, it is not common, with only about 25 species known to attack humans. Shark attacks always make the news, but with less than 100 human attacks annually, you have a better chance of being struck by lightning than being attacked by a shark.
Of the sharks that do go after people, the most dangerous of the lot are Great White’s, Bull shark’s, Tiger sharks, and the Oceanic Whitetip shark. Bull shark attacks are the most common, simply because they live in shallow water, which is where more people congregate.
Many of the attacks come because the shark mistakes the person for a seal or a sea lion which they love to eat. Other types of sharks that have been known to attack humans include Wobbegong, Hammerheads, Mako sharks, Lemon shark, Nurse shark, and a few others.
There will be times when a group of sharks will attack a prey in rather crazy fashion. While this attack is taking place, the sharks in the group will eat anything in sight, including one another.
Where Do Sharks Live?
The oceans and seas of the world are home to sharks, and in areas where the water is warm, sometimes even rivers and lakes. While some sharks prefer the murky depths of the ocean floor, others are more at home in the shallows.
The sharks that live in the open ocean are known as Pelagic sharks, and include the Great White and the Basking shark. The sharks that live on the ocean floor are called Benthic sharks, and they include the Angelshark and Wobbegong.
The shape of their bodies tends to be more flattened, making it easier for them to navigate the ocean bed. The Amazon in Brazil and the Mississippi in the USA are rivers where sharks have been known to call home. The Bull shark has regularly been found living in fresh water regions.
Hammerheads, Bull sharks and Tiger sharks prefer warmer water, whereas temperate waters are home to the likes of the Blue shark, Mako shark, and Basking shark.
The Goblin shark and the Dogfish are much more at home in cooler water. Some sharks are happy to stay in the same area their entire life, while others swim to different regions.
When talking about migration, you need to discuss 3 different types of sharks:
- Local sharks – These sharks never stray more than 100 feet from where they live, and they do not migrate. The Nurse and Bonnethead shark are examples.
- Coastal Pelagic sharks – The Tiger shark, Dusky shark, and Blacktip shark fall into this category. These sharks will migrate as much as 1,000 miles from home.
- Highly Pelagic sharks – The Blue shark and Mako shark fall into this group, which are creatures that migrate across oceans.
Sharks have been around for hundreds of millions of years, and they evolved roughly 100 million years before dinosaurs. We get this information from fossilized teeth and skin impressions.
Some of the earliest sharks were known as Cladodonts, 6-feet long beasts with double-pointed teeth. They swan in our oceans around 360 million years ago.
The Megalodon was a mammoth shark that measured rightly 40-feet in length, and which dominated the oceans millions of years ago. Teeth from this massive beast have been found, and while they are similar to those of a Great White they are about 3 times the size, which equates to the size of a human hand.
The reason that we need to rely on teeth for information is because sharks have no bones, therefore making it impossible for fossils to be discovered.
Endangered And Protected Species
Humans routinely hunt sharks, particularly the larger species, which is endangering certain groups. The Great White, Whale shark, and Basking shark are among the most at risk. The Great White is protected in waters off California and South Africa.
What Species of Shark is the Largest?
The Whale shark is well names, as this species is huge. This monster can grow to be the size of a school bus, which means that it is just shy of 40-feet in length.
Let’s compare that to the most commonly known shark in the world: The Great White. That species grows at a rate of about 10 inches per year until it reaches the average length of about 12-14 feet which is still well short of the Whale shark.
Which Shark is the Most Common?
source: oceanwidelmages.comOf the larger varieties, it is the Ocean Whitetip, which is found in the Atlantic and Pacific Oceans, that is the most common. The Spiny Dogfish is the most common of the smaller species, and is usually found in the North Atlantic.
How Fast are Sharks?
He fastest recorded species is the Shortfin Mao shark, which has been pegged at speeds of 65 mph. To put that in perspective, this shark would be keeping pace with your car on the highway.
Do Sharks Drown if they Stop Swimming?
Yes, there are several shark species that need to be in a constant state of motion in order to breathe. These creatures require the flow of water through their open mouths to breathe properly, so it stands to reason that not moving would cut off that water flow and hamper their ability to breathe.
Some shark species that make their home on the ocean floor are able to breathe when they are still. One example of that is the Carpet shark, which is able to breathe thanks to spiracles that are located behind their eyes.