SHARK SENSES

Many species of shark have brains as complex as those of mammals. Enabling them to process a wide range of senses.

Sharks have the same 5 senses as we do but can also sense electrical currents and pressure changes.


Whitetip Shark nostrils © Ofer Ketter.  

SMELL

Up to two thirds of the total weight of a shark's brain is dedicated to smell.

They’re super-sensitive to smells that are important to their survival. Including scents produced by potential predators, prey or a mate.

Some sharks can detect the blood of prey from a huge distance - one part of blood to one million parts of water. That's equal to one teaspoon in an average sized swimming pool.


Blue Shark eye © Wikimedia Commons, Joxerra Aihartza.
 
 

SIGHT

Light doesn’t travel well through water. So sharks need to maximise the amount available to help them see. With eyes positioned on the side of their head they're able to see in almost all directions. But, their vision becomes more acute 15m from an object. It's not until this point that sight becomes their dominant sense.

Like cats, sharks also have a ‘tapetum lucidum’. A reflective layer of shiny cells that lies behind the retina. This improves vision in low light conditions. Allowing nocturnal and deep-water species to hunt effectively. It also gives their eyes a green glow in the dark.


Catshark © Lauren Smith.  

SOUND

Sharks have an acute sense of hearing and are sensitive to low-frequency signals. They're able to track sounds and are particularly attracted to sounds made by wounded prey.

Their ears are located on either side of their head, behind the eyes. From the outside these are visible as 2 small holes. These are made up of 3 cartilage tubes filled with fluid and lined with hair cells. Sound waves cause these tiny hairs to vibrate and the brain then interprets the sound.


Nurse Shark showing barbels © Shane Gross.  

TOUCH - Sharks have many nerve endings under their skin. Some also have barbells around their mouth that can be used to probe the sand for prey.

Their teeth also contain many pressure sensitive nerves. Lacking hands to feel, sharks will use their teeth to learn more about an object. Being highly inquisitive creatures this can cause a lot of problems. A ‘test bite’ from a large shark can be fatal to unintended prey such as humans.

As well as direct touch, sharks experience distant touch through their lateral line. Read to the end to find out more about this.


Shark hunting a seal © William Buchheit.  

TASTE

The taste organs of a shark are not as highly adapted as their other senses because taste doesn't help them find food.

Sharks will often ‘test bite’ potential food to see if it's palatable. If it's not they'll spit it out.

This could account for the high survival rate of shark victims. Where sharks have bitten people then left without further incident.

ampullae of Lorenzini of a Tiger Shark © Wikimedia Commons, Albert Kok.  

ELECTRORECPTION (ampullae of Lorenzini)

Sharks have a complex electro-sensory system. Enabled by receptors covering the head and snout area. These receptors sit in jelly-filled sensory organs called the ampullae of Lorenzini. These tiny pores are extremely sensitive and can detect even the faintest of electrical fields. Such as those generated by the Earth’s geomagnetic field or muscle contractions in prey.

FUN FACT - Hammerhead sharks can find prey that’s completely buried under the sand. Making them experts at hunting stingrays.

The Earth’s geomagnetic field is thought to help sharks orientate themselves and navigate the world’s oceans. This could explain how they’re able to migrate huge distances so accurately.


Blacktipreef Shark © Alec Connah.  

PRESSURE CHANGES (Lateral Line)

The lateral line is responsible for alerting a shark to potential prey and predators. It’s made up of a row of small pores that run all the way from the snout to the tail. Surrounding water flows through these pores and special sensory cells sense any pressure changes.

The lateral line also gives a shark spatial awareness and the ability to navigate. Their own body movement creates waves that bounce off obstacles (such as reefs). Enabling them to create a pressure map of their surroundings.

There's no human equivalent of this sense. Air isn't dense enough to feel any pressure differences.


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