Sharks are carnivorous fish that live in the ocean. In the wild, sharks play an important role in the food web since they eat a wide variety of fish and provide a nutritious meal to many other animals in the sea.
Sharks are not decomposers but can function as scavengers in the ocean. Whereas they mostly feed as predators eating living animals like other fish, they do also eat dying or dead animals. The Greenland shark is a prime example of a shark that is believed to feed primarily as a scavenger in the arctic regions near Greenland.
However, most sharks are opportunistic feeders that will eat anything they can get. In addition to other fish, their diet can include squid, octopus, crustaceans, mollusks and some larger mammals like whales.
Their diet changes between seasons, as different food types become more abundant or as they grow bigger and can handle larger food items like dolphins and whales.
What are sharks and where are they found?
Sharks are a group of cartilaginous fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head.
They are widely distributed in all seas and live at depths of more than 3,000 m. However, most species prefer to live in relatively shallow coastal waters, but some species, such as the whale shark, prefer the open sea.
Sharks play an important role in marine ecosystems, being quaternary consumers and scavengers; they control the populations of prey species and affect entire food webs.
There are almost 400 known shark species, ranging in size from the small dwarf lanternshark, which attains a length of about 15 cm (5.9 in), to the whale shark, which can reach a length of more than 12 m (39 ft) and a weight of about 6,000 kg (13,200 lb).
What are examples of scavenging sharks?
Almost all sharks are not scavengers as their primary mode of feeding, however, most sharks will not leave a carcass untouched for long if they come across one!
However, some sharks are known to behave more as scavengers than others and are better known of the kind is the Greenland shark.
The Greenland Shark
The Greenland shark is a true scavenger of the sea and may be the only shark that feeds predominantly on carcasses.
It feeds on dead seals, fish, and whales that have sunk to the bottom of the ocean.
Greenland sharks are large, slow-moving scavengers that live in the cold waters of the Arctic and North Atlantic oceans.
These sharks are mostly found in very deep waters of up to 7000 feet (2 km!) where they sniff out their (dead) prey.
Despite their size and slow movement, Greenland sharks are very difficult to study in the wild due to the depths at which they live!
They are rarely seen by humans and much of their behavior and ecology are largely unknown.
What we do know, however, is that Greenland sharks are one of the few species of shark that can live in water temperatures below 0 degrees Celsius (32F). This makes them well-adapted to live in the Arctic, where they are often seen swimming under ice floes.
Like other sharks, the Greenland shark has a great sense of smell that helps it find food.
And although the Greenland shark is one of the slowest-moving sharks in the ocean, as a scavenger, it doesn’t need to swim fast to catch its dinner!
Another reason why the Greenland shark is definitely not in a hurry is its long average lifespan of around 350 years!
The Tiger Shark
Like the Great White Shark, the tiger shark is one of the most feared predators in the ocean. But what do these massive creatures actually eat?
Spoiler: They are very similar to the White Shark!
The tiger shark is a part-time scavenger, which means that it occasionally feeds on the remains of other animals.
They will also eat live prey, but this only makes up a small part of their diet. Carcasses are their preferred food, and they will often swim long distances to find one.
Tiger sharks have been known to eat just about anything, including turtles, dolphins, birds, and even other sharks. If it’s dead and in the water, there’s a good chance a tiger shark will try to eat it!
The Great White Shark
Great white sharks are the largest predatory fish in the world. They are apex predators and have no natural enemies. They generally feed on a variety of animals including other sharks, seals, dolphins, whales, seabirds, fishes, squid, and turtles.
The great white shark was long thought not to scavenge for food, but scientists reveal that it actually eats carrion as part of its diet!
In a recent study, the researchers present findings from multiple observations of white sharks scavenging on whale carcasses in False Bay, South Africa.
The main author of the study said:
Great white sharks normally feed on dead whales, which are important food resources for the solitary predators. During such a feast, when one shark accidently bit another on the head and left two teeth behind, the other sharks showed no aggression toward the biter.Neil Hammerschlag
This indicates that scavenging is part of the social behavior of white sharks.
Similar scavenging behaviors are seen in other fish, which I have written about here.
What makes sharks good hunters and scavengers?
Whereas sharks can be scavengers, they are mostly carnivore hunters that have evolved to catch living prey.
They do this in numerous ways using their optimized bodies, jaws, teeth and super sensitive, vibration, taste, sight and smell senses.
A robust and agile body
The skeleton of a shark is the internal framework of bones, made mostly of cartilage, that encloses the vital organs.
The skeleton also protects and supports the body. There are two main types, the placoid, and the cranium. The placoid type has a cranium (head), two pectoral fins, and two dorsal fins, all attached together, while the cranium and pectoral fins are separate in the cranium type.
The vertebrae, which articulate with each other, are fused into a single ossified mass, the vertebral column. The skull is made up of several parts, or chondrocrania. The ventral (under) surface is flat and smooth, and forms the jaw.
Strong jaws and sharp teeth!
Sharks have a number of physical adaptations for capturing prey, such as sharp teeth, tough gums, and tough skin.
The jaws, located just behind the large gill slits, are lined with serrated teeth. The outside of the jaw is lined with placoid scales. The jaws are attached by ligaments and muscles, rather than by strong bones.
Shark teeth are modified scales, and consist of several rows of teeth, each tooth being triangular in cross-section.
The upper jaw usually has a larger, serrated, triangular tooth, with teeth on the lower jaw much smaller and finer, and in many species, not serrated.
Because a shark can have many rows of teeth, some sharks like the great white shark can have more than 1000 teeth!
The teeth of sharks are embedded in the gums, and they are not replaced when they fall out.
Shark saliva contains the enzyme kallikrein, which liquefies blood, and anticoagulants that prevent the blood from clotting so its prey will die faster.
Sharks have well-developed senses, which include sensitivity to electrical fields, vibrations and chemicals.
Their gill slits are lined with sensory organs, called neuromasts, which can detect low-frequency vibrations.
They can detect minute vibrations in the water created by the movement of other animals, such as potential prey. Sharks can sense water displacements as small as 10-20 μm!
The eye is well developed but not as good as other apex predators, with a retina, lens, and iris. It extends both anteriorly and posteriorly and is shaped like a cone.
The pupil is elliptical and is surrounded by a diaphragm, or third eyelid, which aids in reducing glare so they are not distracted by light and spotted by their prey.
The mouth has sensory organs called the ampullae of Lorenzini, which detect electrical signals generated by potential prey. These electrical signals are generated by neurons of all living animals and are conducted by saltwater.
This is a unique detection strategy that allows the shark to hunt even in pitch darkness.
The olfactory lobes are used to detect chemical signals in the water.
The lateral line system allows sharks to detect vibrations in the water, which could indicate the presence of potential prey.
What is the Diet of Sharks?
Smaller species tend to eat more fish, squid, octopus, crabs, shrimp, and similar animals or their remains; larger sharks also eat these but in smaller proportions than smaller species.
Sharks are predators, feeding on fish, invertebrates, and occasionally other organisms. However, the feeding ecology of sharks varies markedly among species and sharks are opportunistic predators, feeding on whatever prey is available.
Most sharks primarily eat fish, but they will also consume squid, crustaceans, mollusks, and even marine mammals. Their diet changes between seasons and as they grow older, with larger sharks able to eat bigger prey items.
Some of the items sharks eat are:
- baleen whales
- sea turtles
- other sharks
- and sometimes, but rarely, humans.
However, sharks eat different things depending on their environments. Most places in the sea, sharks eat fish, and other places sharks may mostly eat squid or jellyfish.
Are Sharks Decomposers?
Sharks are not considered decomposers because they mostly eat meat from living animals!
Most sharks are predators, but some, like the Greenland shark, are primarily scavengers.
Sharks feed on primary consumers such as fishes, birds, seals, turtles, amphibians, reptiles, mammals, birds, squid, jellyfish, crustaceans, worms, snails and other shellfish.
Are Sharks Carnivores, Herbivores or Omnivores?
Sharks are carnivores because they mostly eat animals. They are also known as fish eaters.
Sharks are also considered scavengers, because they eat dead and decaying things that may otherwise decompose in the ocean or in landfills.
But all sharks are carnivores as they mostly eat fish, including herring and salmon, but may eat other meat, such as seals and other sharks.
Is a Shark a Producer or a Consumer?
Sharks are consumer because they mostly eat meat. Sharks are also considered scavengers because they eat dead bodies or bones of creatures such as birds, mammals and fish.
Sharks are not considered producers because they do not make their own food from the water and do not make their own food from the sun.
What Animals Hunt and Eat Sharks?
While sharks may be apex predators at the top of the food chain, they are not without their own predators.
Some of the most common predators of smaller or juvenile sharks are large fish like tunas and other sharks like great white sharks, but also squids octopuses, or large birds like eagles, who will sometimes eat sharks for food.
Humans also pose a threat to sharks through hunting and habitat destruction. Most sharks are caught as by-catch in commercial fisheries targeting other fish.
But sharks are also considered valuable commodities in some cultures, sometimes being sold for high prices as food, leather, and shark liver oil. In many countries, shark populations have declined due to overfishing.
What decomposers eat sharks when they die?
When a shark dies, it is likely that other sharks and marine life will come and eat the shark. Sometimes, sharks will be scavenged by marine mammals or birds as well.
The scavengers and decomposers that eat a dead shark will be similar to the decomposers and scavengers that eat other sea creatures like a dead seal or tuna.
Bacteria will eat the shark’s meat and bones, and the sharks skin and fins will be eaten by marine life like worms, scavenging fish, or crustaceans.
The last remains of a dead shark will be eaten by bacteria and small marine life for many months or years.
After a year or so, nothing is left and sharks can be considered completely decomposed.
Sharks are opportunistic feeders and will consume a wide variety of food items but they are not considered decomposers sharks are scavengers, which means they eat dead animals and their waste.
Sharks are apex predators, preying on a wide variety of organisms from fish, crustaceans, and molluscs to turtles, birds, and marine mammals.
Most sharks are active hunters, primarily feeding by sight. Sharks possess excellent senses of smell and hearing, but poor eyesight. They have special organs that detect electrical fields emitted by prey.
Sharks are important because they are top predators and scavengers, and they are able to consume a lot of their prey.
Whereas sharks are not decomposers, they are a great example of how important it is to keep our oceans clean.
Sharks are also important for the ecosystem because they play a vital role in regulating the populations of other animals.
Sharks are a very misunderstood group of animals, but they are also very important for the ecosystem!