When we think about sharks, the first image that usually comes to mind is a fearsome predator sniffing out blood in the water from miles away. While it’s true that sharks have an impressive sense of smell, my view is that their ability to detect blood isn’t as powerful as many believe. From my learnings of acoustics, I believe that sharks might rely more heavily on their sense of hearing, especially when detecting splashing sounds from far away, rather than blood scent alone.
Sharks: The Masters of Multi-Sensory Hunting
Sharks are apex predators, evolved to be exceptional hunters. They have a range of sensory systems that help them locate prey:
1.Olfaction (Sense of Smell): Sharks are renowned for their keen sense of smell, which can detect blood in water at dilutions as low as one part per million. However, the perception that they can smell blood from several kilometers away according to me is a myth. The detection range for scent alone would be much shorter, especially considering how scent disperses in the ocean.
2.Hearing: Sharks would have an acute sense of hearing, which is one of their most powerful long-range detection abilities. Sound travels faster and farther in water than it does in air, allowing sharks to hear low-frequency sounds, such as the splashing and flapping of a struggling fish, which some believe from up to 4 kilometers away. The low-frequency noises produced by prey in distress, such as splashing, are particularly enticing because they mimic the sounds of injured or struggling fish, signaling an easy meal.
3.Lateral Line System: This unique system allows sharks to detect vibrations and pressure changes in the water, aiding them in sensing nearby movements. This helps sharks pinpoint the exact location of their prey when they are close enough to feel the water’s subtle vibrations.
4.Electroreception: Sharks also possess electroreceptors called ampullae of Lorenzini, which detect the weak electric fields generated by living organisms. This sense becomes crucial when the shark is in close proximity to its target, as it helps locate prey even when it is hidden or camouflaged.
When a fish or a swimmer splashes, the resulting noise creates ripples of low-frequency sounds that travel rapidly through water. These low-frequency sounds can be detected by sharks over great distances. In essence, sharks might be more likely to detect the auditory cues of struggling prey long before they catch the scent of blood. This is why surfers, swimmers, and splashing fish are often more likely to attract sharks. The splashing sound mimics that of an injured animal, which the shark interprets as a potential easy meal.
Blood: The Final Clue
While the myth of sharks being able to smell blood from miles away is exaggerated, the scent of blood does play a crucial role when a shark gets closer to its prey. The release of blood or bodily fluids into the water acts as a secondary cue, guiding the shark to its target when it is in closer proximity.
Blood, being denser than water, disperses more slowly, and its detection requires the shark to be relatively closer to the source compared to hearing the splashes. The scent trail helps to confirm the presence of injured prey and assists the shark in honing in on its exact location.
How Can This Information Help Us?
Understanding the importance of sound in shark detection can help in reducing human-shark interactions. For instance:
1.Avoiding Splashing: Swimmers and surfers are often advised to avoid excessive splashing, especially in waters known to be frequented by sharks. Staying calm and minimizing noise reduces the risk of drawing attention.
2.Using Sound Deterrents: Researchers have explored using specific sounds as shark deterrents. High-frequency, unnatural noises may help to repel sharks, as they are not typically associated with prey.