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How do sharks find their prey?

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Built like a living, breathing guided missile, sharks use a variety of senses to detect and zero in on their prey.
Built like a living, breathing guided missile, sharks use a variety of senses to detect and zero in on their prey.

By Blaise Jones

While sharks are often compared to torpedoes, they’re really more like guided missiles. Beneath their tough exterior of teeth, muscles, and tough skin, there is a shockingly complex system of delicate sensory systems that let sharks zero in on their prey.

Swimming noses

While sharks rely on all of their senses to find their prey, the sense of smell is probably their single greatest asset. Sharks rely on their sense of smell so much that they are often referred to as “swimming noses.” Depending upon the species, a shark’s olfactory bulbs can take up between 3-14 percent of their total brain mass. This allows a shark to sense even the slightest of scents, even as small as one part scent molecule in 10 billion water molecules.

Scent trails can travel for miles. and with their strong sense of smell sharks can detect prey miles away and follow it back to the source.

Specialized nose

While shark noses are extraordinarily sensitive, they are also highly specialized and able to detect much more than just blood. Certain amino acids, the building blocks of proteins, are more affective at drawing in sharks than even blood. Amino acids are released in excrement when fish defecate, helping sharks find them in any condition. Fish also create amino acids when healing, which signals to a shark’s nose which fish might be injured and make for easier prey.

Certain species of shark, such as the great white, are highly attuned to pheromones released by their own species. Great whites have specialized nerves in their brain dedicated specifically to detecting pheromones released by other great whites which allow them to do many things including finding a mate and knowing when to flee a predator or assault.

Hearing

A shark’s sense of hearing is equally helpful in finding prey because sound travels incredibly far distances through water. Sharks can detect sounds between 20 -1100 Hertz, which is roughly equal in range from the low boom of thunder to the higher end of the human voice.

The sound of an injured fish can generate pressure waves at low frequencies, and sharks are highly responsive to low frequencies noises. The noises an injured fish make can travel as far as 650 feet (198 m), giving a shark another way to detect prey at a distance.

Sight, Touch, and Shocks

Once a shark has used its sense of smell and hearing to narrow down the location of its prey, it begins using its less sensitive senses to pinpoint its location. First comes a shark’s sense of sight. While sight is not the most useful sense in dark and murky water, sharks have developed excellent vision to counter act the conditions.

They possess adaptations similar to cats that allow their eyes to absorb light, which boosts their eyesight underwater similar to how a cat has better eyesight than other mammals at night. Sharks appear to need all the help they can get for long-distance eyesight because studies indicate that shark’s eyes are more focused on distance, and that a shark’s vision blurs at around 9 inches (23 cm).

As a shark sees its prey and begins the actual chase, it’ll begin to rely on its lateral line. The lateral line allows a shark to sense the movement of its prey via the pressure waves it creates in the surrounding water as it moves. Imagine if you were able to chase after somebody with your eyes closed by feeling the wind they create by the movements of their arms and legs and that would approximate the sense a shark has with its lateral line.

As the shark closes in for the kill, he relies on its ability to detect electromagnetic pulses thanks its ampullae of Lorenzini, which are extremely sensitive at close range and allow a shark to sense the electrical pulsations of its prey’s muscles within a certain distance. For example, a human-sized animal moving through the water would produce enough electricity for a shark to detect him at around 3-6 feet (1-2m). A shark will be able to detect bigger prey items at further distances and smaller ones at shorter distances with their ampullae, allowing them to pinpoint their prey’s location.

Once the shark begins to bite a nictitating membrane will cover the eyes like a pair of eyelids or goggles, preventing their eyes from getting cut or injured during predation.

 

Sources

  1. “Sharks: The Animal Answer Guide” by George H. Burges and Gene Helfman
  2. “The Encyclopedia of Sharks” by Steve A. Parker
  3. http://www.aminoacid-studies.com/amino-acids/what-are-amino-acids.html
 
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