Sharks: Predators with a Purpose!

Amazing Fact: Sharks can detect one drop of blood dissolved in a million gallons of water! These predators with a purpose have existed for over 400 million years, long before dinosaurs walked the Earth. Far from primitive, sharks possess incredible senses that make them perfectly adapted to their ocean environment.

Ancient Yet Sophisticated

A picture of a shark with the various parts labeled
Click to enlarge

Sometimes sharks are referred to as primitive creatures. They are an ancient group of animals, so it might seem correct to assume that they are primitive. Unfortunately, this assumption is wrong.

Recent studies have shown that sharks are, in fact, quite sophisticated. Are these the attributes of a primitive animal?

Incredible Sense of Smell

Most sharks have an incredible sense of smell. These sharks can detect one drop of blood dissolved in as much as one million gallons of water!

Electroreception

Many sharks can detect the extremely minute electrical currents generated by the muscles of swimming fish. This ability, called electroreception, allows them to sense prey even when it’s hidden.

Pressure Detection

Some sharks can sense at a great distance the tiny pressure variations generated by an injured fish struggling to swim. This lateral line system helps them detect movement in the water.

Excellent Vision

Contrary to popular opinion, most sharks have excellent low light vision, thanks to a mirror located behind the retina. This mirror, called the tapetum lucidum, reflects light through the retina a second time, enhancing their ability to see in murky water.

Self-Replacing Teeth

A shark may have many rows of teeth. When an old tooth breaks or becomes too dull, a new one rotates into place. Some sharks go through thousands of teeth in their lifetime!

Diversity of Sharks

Sharks come in many shapes and sizes. The largest fish in the ocean is, in fact, the tremendous whale shark, reaching about 60 feet in length. The smallest known shark is only a few inches long when fully grown.

While many sharks do have conspicuous teeth, many of these animals eat only small invertebrates. Other sharks have no teeth at all, feeding by straining plankton from the water much like the baleen whales do.

Gray reef shark swimming among a school of fish.

Grey Reef Shark

The Grey Reef shark (Carcharhinus amblyrhynchos) is common around Pacific coral reefs, feeding mostly on fish and invertebrates. They reach a little over 7 feet in length.

These sharks tend to swim together in groups, unlike most other sharks, making them dangerous, even though they are small.

Basking shark swimming underwater in a close-up view.

Basking Shark

The Basking Shark (Cetorhinus maximus) is a filter feeder, and eats only zooplankton and small fishes. The filter-feeding scheme works well: the Basking Shark can grow to 45 feet, making it the world’s second largest fish.

This shark inhabits the cooler temperate regions of the world’s oceans. It is frequently mistaken for a whale as it cruises just at or below the surface straining plankton.

Scalloped hammerhead shark swimming underwater.

Scalloped Hammerhead

The Scalloped Hammerhead in the Galapagos Islands is extremely frightened of divers’ bubbles. These distinctive sharks use their unique head shape to enhance their electroreception abilities and to pin prey to the ocean floor.

Great white shark swimming underwater viewed from the side.

Great White Shark

One of the most dangerous sharks in the world, the Great White (Carcharodon carcharias) is perhaps best known for its role as the antagonist in the film “Jaws.”

This large, aggressive shark has indeed been known to attack people on occasion, although attacks are quite rare. Great Whites may reach 21 feet in length and weigh over 2,500 pounds. They inhabit all of the temperate (cool) oceans.

Shark Facts

400+ Million Years Old

Older than dinosaurs!

1:1,000,000

Blood detection ratio in water

60 Feet

Whale shark – largest fish

Lightning > Sharks

More likely to be struck by lightning than attacked

Endangered

Populations declining worldwide

Shark Gallery

The Whale shark (Rhincodon typus) is the largest fish on Earth, possibly reaching 60 feet in length, or about as long as two school buses! This whale shark has a remora riding on it's head. (The remora is a kind of fish that acts like a suction cup, attaching to larger animals to get a free ride).

The Whale shark (Rhincodon typus) is the largest fish on Earth, possibly reaching 60 feet in length, or about as long as two school buses! This whale shark has a remora riding on it’s head. (The remora is a kind of fish that acts like a suction cup, attaching to larger animals to get a free ride).

The Whale shark (Rhincodon typus) is the largest fish on Earth, possibly reaching 60 feet in length, or about as long as two school buses! This whale shark has a remora riding on it’s head. (The remora is a kind of fish that acts like a suction cup, attaching to larger animals to get a free ride).

The Scalloped Hammerhead in the Galapagos islands. This shark is extremely frightened of divers bubbles.

The Scalloped Hammerhead in the Galapagos islands. This shark is extremely frightened of divers bubbles.

The Scalloped Hammerhead in the Galapagos islands. This shark is extremely frightened of divers bubbles.

The Grey Reef shark (Carcharhinus amblyrhynchos) is common around Pacific coral reefs, feeding mostly on fish and invertebrates. They reach a little over 7 feet in length. These sharks tend to swim together in groups, unlike most other sharks, making them dangerous, even though they are small. Photo by Jonathan Bird

The Grey Reef shark (Carcharhinus amblyrhynchos) is common around Pacific coral reefs, feeding mostly on fish and invertebrates. They reach a little over 7 feet in length. These sharks tend to swim together in groups, unlike most other sharks, making them dangerous, even though they are small. Photo by Jonathan Bird

The Grey Reef shark (Carcharhinus amblyrhynchos) is common around Pacific coral reefs, feeding mostly on fish and invertebrates. They reach a little over 7 feet in length. These sharks tend to swim together in groups, unlike most other sharks, making them dangerous, even though they are small. Photo by Jonathan Bird

The Basking Shark (Cetorhinus maximus) , is a filter feeder, and eats only zooplankton and small fishes. The filter-feeding scheme works well: the Basking Shark can grow to 45 feet, making it the world's second largest fish. This shark inhabits the cooler temperate regions of the world's oceans. It is frequently mistaken for a whale as it cruises just at or below the surface straining plankton. Photo by Jonathan Bird

The Basking Shark (Cetorhinus maximus) , is a filter feeder, and eats only zooplankton and small fishes. The filter-feeding scheme works well: the Basking Shark can grow to 45 feet, making it the world’s second largest fish. This shark inhabits the cooler temperate regions of the world’s oceans. It is frequently mistaken for a whale as it cruises just at or below the surface straining plankton. Photo by Jonathan Bird

The Basking Shark (Cetorhinus maximus) , is a filter feeder, and eats only zooplankton and small fishes. The filter-feeding scheme works well: the Basking Shark can grow to 45 feet, making it the world’s second largest fish. This shark inhabits the cooler temperate regions of the world’s oceans. It is frequently mistaken for a whale as it cruises just at or below the surface straining plankton. Photo by Jonathan Bird

Great white shark swimming underwater viewed from the side.

Great white shark swimming underwater viewed from the side.

Tiger shark

Tiger shark

Tiger shark

A picture of a shark with the various parts labeled

The parts of a shark

How do you tell a male from a female shark? The picture above shows a MALE. The male has a pair of claspers at the base of the pelvic fins.

How do you tell a male from a female shark? The picture above shows a MALE. The male has a pair of claspers at the base of the pelvic fins.

How do you tell a male from a female shark? The picture above shows a MALE. The male has a pair of claspers at the base of the pelvic fins.

This is a female, showing a lack of claspers on the pelvic fins.

This is a female, showing a lack of claspers on the pelvic fins.

This is a female, showing a lack of claspers on the pelvic fins.

The Truth About Shark Attacks

The myth that sharks are maneaters has been established throughout history with startling regularity. The fact is, you are much more likely to be hit by a car, bitten by a dog, or even struck by lightning than you are to be attacked by a shark, except under the most unusual of circumstances.

Certainly sharks can eat people, but the simple fact is that they rarely do. They are no more dangerous to people than any other large predator, like a tiger or a lion.

Important Question: Why do we label the shark a killer, while we call the lion magnificent?

Ecological Importance

Top Predators

Sharks are very important in the ocean ecosystem. Like most top predators, sharks feed on the sick and weak, thereby keeping the schools of fish on which they feed healthy.

Lions and tigers serve the same role in their respective ecosystems, removing the weaker animals from the herds, and keeping the gene pool strong.

Conservation Crisis

Although it has long been said “The only good shark is a dead one,” sharks have a very important role in the ocean ecosystem, and they most certainly are not better off dead. Believe it or not, we need sharks in the oceans.

Shark populations are dwindling due to heavy commercial fishing and the general attitude that they are nothing more than a nuisance. This shortsighted view of the ocean ecosystem is dangerousba shortage of sharks could be disastrous to the health of ocean food chains, including but certainly not limited to the ones we rely upon for food resources.

We humans are already placing enough strain on these food chains as it is, without adding the shark to the equation. We must respect these animals and give them the space they need to live.

Bottom Line: Sharks really are beautiful animals…once you get to know them.

Shark Anatomy

Male vs Female Identification

How do you tell a male from a female shark?

Ventral anatomy of a male shark showing claspers.

Male sharks have a pair of claspers at the base of the pelvic fins. These are reproductive organs used for internal fertilization.

Ventral anatomy of a female shark showing fin placement.

Female sharks show a lack of claspers on the pelvic fins, having only the cloaca opening.

Shark Facts

400+ Million Years Old

Older than dinosaurs!

1:1,000,000

Blood detection ratio in water

60 Feet

Whale shark – largest fish

Lightning > Sharks

More likely to be struck by lightning than attacked

Endangered

Populations declining worldwide

Shark Gallery

The Whale shark (Rhincodon typus) is the largest fish on Earth, possibly reaching 60 feet in length, or about as long as two school buses! This whale shark has a remora riding on it's head. (The remora is a kind of fish that acts like a suction cup, attaching to larger animals to get a free ride).

The Whale shark (Rhincodon typus) is the largest fish on Earth, possibly reaching 60 feet in length, or about as long as two school buses! This whale shark has a remora riding on it’s head. (The remora is a kind of fish that acts like a suction cup, attaching to larger animals to get a free ride).

The Whale shark (Rhincodon typus) is the largest fish on Earth, possibly reaching 60 feet in length, or about as long as two school buses! This whale shark has a remora riding on it’s head. (The remora is a kind of fish that acts like a suction cup, attaching to larger animals to get a free ride).

The Scalloped Hammerhead in the Galapagos islands. This shark is extremely frightened of divers bubbles.

The Scalloped Hammerhead in the Galapagos islands. This shark is extremely frightened of divers bubbles.

The Scalloped Hammerhead in the Galapagos islands. This shark is extremely frightened of divers bubbles.

The Grey Reef shark (Carcharhinus amblyrhynchos) is common around Pacific coral reefs, feeding mostly on fish and invertebrates. They reach a little over 7 feet in length. These sharks tend to swim together in groups, unlike most other sharks, making them dangerous, even though they are small. Photo by Jonathan Bird

The Grey Reef shark (Carcharhinus amblyrhynchos) is common around Pacific coral reefs, feeding mostly on fish and invertebrates. They reach a little over 7 feet in length. These sharks tend to swim together in groups, unlike most other sharks, making them dangerous, even though they are small. Photo by Jonathan Bird

The Grey Reef shark (Carcharhinus amblyrhynchos) is common around Pacific coral reefs, feeding mostly on fish and invertebrates. They reach a little over 7 feet in length. These sharks tend to swim together in groups, unlike most other sharks, making them dangerous, even though they are small. Photo by Jonathan Bird

The Basking Shark (Cetorhinus maximus) , is a filter feeder, and eats only zooplankton and small fishes. The filter-feeding scheme works well: the Basking Shark can grow to 45 feet, making it the world's second largest fish. This shark inhabits the cooler temperate regions of the world's oceans. It is frequently mistaken for a whale as it cruises just at or below the surface straining plankton. Photo by Jonathan Bird

The Basking Shark (Cetorhinus maximus) , is a filter feeder, and eats only zooplankton and small fishes. The filter-feeding scheme works well: the Basking Shark can grow to 45 feet, making it the world’s second largest fish. This shark inhabits the cooler temperate regions of the world’s oceans. It is frequently mistaken for a whale as it cruises just at or below the surface straining plankton. Photo by Jonathan Bird

The Basking Shark (Cetorhinus maximus) , is a filter feeder, and eats only zooplankton and small fishes. The filter-feeding scheme works well: the Basking Shark can grow to 45 feet, making it the world’s second largest fish. This shark inhabits the cooler temperate regions of the world’s oceans. It is frequently mistaken for a whale as it cruises just at or below the surface straining plankton. Photo by Jonathan Bird

Great white shark swimming underwater viewed from the side.

Great white shark swimming underwater viewed from the side.

Tiger shark

Tiger shark

Tiger shark

A picture of a shark with the various parts labeled

The parts of a shark

How do you tell a male from a female shark? The picture above shows a MALE. The male has a pair of claspers at the base of the pelvic fins.

How do you tell a male from a female shark? The picture above shows a MALE. The male has a pair of claspers at the base of the pelvic fins.

How do you tell a male from a female shark? The picture above shows a MALE. The male has a pair of claspers at the base of the pelvic fins.

This is a female, showing a lack of claspers on the pelvic fins.

This is a female, showing a lack of claspers on the pelvic fins.

This is a female, showing a lack of claspers on the pelvic fins.

Explore More Wonders

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Coral Reefs

Echinoderms

Cnidarians

Mollusks

Sperm Whales

Chessie

Mangroves

Arthropods