What Do Sharks Eat and Why We Shouldn't Be Scared of Them?

Food of Great White Sharks
Sharks were known as 'sea dogs' until the 16th century. Although the history behind the origin of their name is uncertain, one thing remains common - they are still regarded as one of the most feared marine organisms. Great white sharks feed on fish (including other sharks) and cetaceans, such as dolphins and whales, sea turtles, sea lions, and sea otters. They usually prefer prey having a high amount of energy-rich nutrients and fat.
Did You Know?
Every night, the pygmy shark travels for close to 1,500 meters to and fro from the ocean floor in search of food. The energy spent roughly equals 7 miles if a human decides to climb the same distance.
Sharks belong to the subclass Elasmobranchii of the class Chondrichthyes and are found till the depths of 2000 meters, exclusively in seawater -- exceptions being the bull shark and the river shark, which are found in both seawater and freshwater.

Although the kind of food that sharks eat is more or less the same, it is interesting to know the various mechanisms they resort to while feeding.

Let's delve in detail on what do sharks eat and how they capture their prey.
Diet
Sharks are classified into more than 470 species ranging in different sizes. Species, such as the tiger shark, great white shark, blue shark, hammerhead shark, and mako shark are apex predators. Apex predators are those that are present at the top of their food chain (in this case, the underwater food chain) and are not fed upon by anyone.
» Also called "garbage cans of the sea", tiger sharks are well-known to feed on absolutely anything edible. These opportunistic feeders have a diet comprising largely small fish and their carrion, along with larger marine animals, such as dolphins and other sharks, like sandbar sharks and rays. They play an important role in the marine ecosystem by feeding on sea turtles and sea snakes.
» Squids form the major part of the diet of blue sharks along with bony fish, cuttlefish, lobsters, shrimp, octopuses, and other small sharks.
» Hammerhead sharks' most preferred food is the stingrays. They are also known to feed on several other organisms, which include squids, fish, crustaceans, and other sharks.
Do Sharks Eat Humans?
shark and human
The popular belief that sharks feed on humans too, is in fact not true. Out of the total number of species of sharks found today, only 4 species are so far recorded to attack humans -- great white sharks, tiger sharks, bull sharks, and arguably oceanic whitetip sharks. The most logical explanation given by scientists that negate the fact that sharks love to feed on humans is that the evolution of sharks took place years before humans, thus people do not feature on the normal diet plan of a shark
The attacks that take place have, more often than not, found out to be a result of curiosity and a possible fact that they smell uncanny elements on or nearby a diver, which might range from the material that the diving suits are made of, to other equipment. Usually, people are advised not to enter the water if they have bruises or cuts because even small traces of blood can provoke a shark and lead to an attack. Otherwise, if a shark sees people splashing water, swimming, or snorkeling, they happen to approach them by sheer curiosity.
Feeding Techniques
Filter Feeding
Filter Feeding
As the name suggests, certain sharks feed by filtering the food matter, such as zooplankton, and other small fish from the water through a process where the water is passed through a detailed filtering mechanism. Among the shark subclass, whale shark, megamouth shark, and basking shark are filter feeders.

» Megamouth Shark - This shark uses gill rakers for filter feeding but also possesses luminous light-emitting organs called photophores, which are believed to attract the prey into its mouth.
» Basking Shark - The basking shark cannot suck water, and the only way it can take in water is when it enters through gills while swimming. Thus, a basking shark is not a direct filter feeder but has been observed to filter up to a ton of food at one time.

» Whale Shark - Whale sharks take in water along with its prey and strain the organisms by utilizing a spongy tissue present between the gill arches. Thus, they expel the excess water by using the gills instead of gill rakers.
Ram Feeding
Ram Feeding
Ram feeding involves moving of the shark in the direction of its prey and engulfing the prey along with the water. Unlike filter feeding, where the predator stays in a fixed place and attracts the prey, ram feeding is carried out by the predator's movement while the prey stays rooted in one place. After engulfing the prey along with water, the excess water is released through means of the gills. Basking sharks are believed to use this mechanism of feeding.
Suction Feeding
Here, the predator sucks the prey into its mouth and digests it. Suction is possible when the fish imposes a great deal of volume on its throat, producing a difference in the pressure within the fish and its surroundings. This pressure difference results in the movement of water along with the prey into the mouth of the fish.
» Nurse Shark - In order to feed on prey hiding in crevices, nurse sharks make use of their thick lips to create a suction that helps them capture their prey.

» Cookiecutter Shark - Using its suctorial lips, the cookiecutter sharks are believed to suck their prey into a well-rounded circle removing chunks of flesh of marine organisms of any size. Along with the lips, it uses its large triangular teeth to suck and carve out pieces of flesh from its prey.
Other Mechanisms
» Thresher sharks possess a long tail, which they use effectively to petrify their prey before consuming it.
» A saw fish moves its head sideways to kill the prey with its long rostrum (snout), also using it to dig out the prey hiding beneath the sand.
» Saw sharks have a similar snout like that of the saw fish, but with alternating saw teeth which they use to injure small fish.
» Sharks, such as the whitetip reef shark hunts in groups to trap a prey. They are often observed migrating to different waters in search of food.
» The peculiar flattened shape of the head of a hammerhead shark helps it to peg down or trap the prey, and feeds on it only after it is sure that the prey is disabled or weak.
» Several shark species are bottom feeders, where they use their upper jaw to hold the prey. Species, such as horn sharks possess two types of teeth; one set is used to clasp the prey and the other set for squeezing or crushing it.
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» Some sharks, for example angel sharks, are found in the benthic (lowest level of a water body) zone and await their prey using the sand as a camouflage, attacking it when it approaches them.
Although the threats that sharks pose on humans have largely been blown out of proportion, there are records of white shark and tiger shark attacking humans in an unprovoked state. This has led to the increase in fear among people, resulting in extensive fishing and shark finning. Thus, the IUCN in 2009, released a list of 64 shark species, which face the possibility of extinction.