Here in Gansbaai, South Africa we are lucky enough to see one of the oceans ultimate apex predators – the great white shark. One of the reasons great white sharks became a top ocean predator is due to their highly adapted senses. Sharks have the same five senses as us humans….but they also have two extra senses:

Smell

Sound

Taste

Touch

Vision

Pressure changes/ vibrations

Electroreception

A sharks sense of smell is arguably one of their most important senses as roughly two thirds of its brain is dedicated to smell.

So, lets have a look at how sharks are able to sniff out their prey….

A shark’s sense of smell is very important for detecting food and also pheromones for mating. Sharks have a very acute sense of smell and an extremely sensitive olfactory system – the part of the sensory system used for smelling. The olfactory organs (or the nose) in animals are responsible for receiving and interpreting odours.

Just under the shark’s snout, there are two nares (nostril-like holes) and each nare is divided by a nasal flap into two openings. Sharks are able to detect food or a mate because water is constantly flowing into the nares, allowing scents from the surrounding environment to enter the canals and nasal sacs. The water flows over folds of skin known as the olfactory lamellae, which greatly increase the surface area in the nasal sacs, allowing a shark more opportunity to detect odours. Odours passing over the olfactory lamellae stimulate sensory cells which then send messages to the brain. The olfactory lobes in the shark’s brain interpret the stimuli and provide information back to the shark regarding location, nature and distance of the prey.

Photographs of the brains of the lemon shark (N. brevirostris) showing the organisation of the olfactory bulbs in sharks (Meredith et al, 2003)

What about the great white shark?

The great white’s olfactory organs are huge, with long olfactory tracts and well developed lamellae – which increase their surface area and thus greatly enhance sensitivity.

Like other sharks, olfaction (smell) takes place in the nasal cavities but incredibly up to 18 per cent of a great white’s brain mass is dedicated to smell, making it the highest percentage among sharks. Great whites have the largest olfactory bulbs – relative to body size – of any elasmobranchs (sharks and rays), which suggests that scent is very important in this shark’s sensory world. A great white’s sense of smell allows it to detect minute traces of chemicals in the surrounding water and then follow the trace back to its source, which can sometimes be several kilometres away. The great white’s sense of smell is not only used to find food, but probably also plays an important role in social situations, such as mating.

For example, when a great white is in Gansbaai it may pick up the stench of its local 5* restaurant, Geyser Rock, which has at least 60,000 stinky Cape fur seals on…. Or even catch the scent of a prospective Mrs Great White Shark when it is travelling the world.

Geyser Rock, Gansbaai packed full of Cape fur seals

Sense of direction…

The most amazing fact about a shark’s sense of smell is that it is directional. Sharks have twin nasal cavities which means that smell coming from the left of the shark will enter the left cavity just before it arrives at the right cavity. This means the shark can tell exactly where the scent is coming from.

At White Shark Projects we use a method called chum to attract sharks to our cage diving vessel, Shark Team. We mix oily fish with sea water and mash it up to release the oils and create a soup. This smelly oily soup then gets thrown into the sea to create a chum slick – a scent trail for a shark to follow to our boat. If a shark passes through our chum slick it will follow the scent moving its head from side to side (natural swimming motion for a shark). As its snout passes backwards and forwards through the scent trail it will able to determine the direction from which the odour is coming from and follow it to the strongest point – hopefully our boat, Shark Team!

Great white sharks have highly-developed senses that are adapted to their ocean environment, making them one of the world’s top predators. We feel privileged to see the beauty of this unique ocean predator right here in Gansbaai. To learn more about how incredible sharks are – read our previous blogs.