Do Sharks Make Noises? A Deep Dive into Shark Communication

Sharks are often depicted as silent hunters, gliding through the ocean without a sound. Unlike many marine animals that rely on vocalizations for communication, sharks lack vocal cords or specialized sound-producing organs, leading to the widespread belief that they are completely mute.

However, some reports suggest certain species may produce noises under specific conditions. While evidence remains limited, scientists continue investigating whether these sounds are intentional communication or incidental byproducts of movement.

Anatomy Involved In Potential Sound Production

Sharks have a skeletal structure composed primarily of cartilage rather than bone, which affects their ability to generate sound. Unlike bony fish that may use swim bladders to produce noises, sharks lack this organ, eliminating a common mechanism for underwater vocalization. Their streamlined bodies are designed for efficient movement, minimizing turbulence and reducing incidental sound production.

Despite the absence of dedicated vocal structures, certain physical interactions with the environment could generate noise. The forceful expulsion of water through gill slits has been proposed as a potential source of sound, though no definitive evidence supports this as a deliberate form of communication. Similarly, rapid jaw movements during feeding might create audible clicks or snaps, but these are likely byproducts of mechanical action. Some species, like the nurse shark (Ginglymostoma cirratum), produce a sucking or rasping noise when feeding, attributed to suction mechanics rather than vocalization.

The dermal denticles covering a shark’s skin reduce drag and turbulence, allowing for near-silent movement. However, sudden contact with a surface or rapid directional changes could create subtle noises due to friction between the denticles and surrounding water. While these sounds are not vocal in nature, they highlight how a shark’s anatomy interacts with its environment in ways that might produce incidental auditory effects.

Observed Vocal Traits In Select Species

Despite the belief that sharks are voiceless, some anecdotal reports suggest certain species may produce sounds under specific conditions. These accounts describe noises such as low-frequency clicks, growls, and even barking-like sounds. The epaulette shark (Hemiscyllium ocellatum), for example, has been noted to emit clicking noises when agitated or handled, though the precise mechanism remains unclear. Some researchers speculate these clicks result from the movement of skeletal structures or the forceful expulsion of water rather than an intentional vocalization system.

The draughtsboard shark (Cephaloscyllium isabellum), known for inflating its body when threatened, has been observed making a growling noise during this defensive behavior. This sound appears to be a byproduct of air or water being forced through internal cavities as the shark expands rather than an intentional signal. Still, its repeated occurrence in response to threats raises questions about whether such sounds could help deter predators.

Another species of interest is the swell shark (Cephaloscyllium ventriosum), which has been reported to make a barking-like noise when removed from the water. This phenomenon seems to result from the expulsion of trapped air within the stomach or esophagus. Given the lack of specialized vocal structures, these sounds are likely secondary effects of other physiological functions rather than adaptations for acoustic signaling.

Non-Vocal Communication Methods

While sharks do not rely on vocalizations, they employ a variety of non-verbal strategies to interact with their environment and other marine organisms. These include body language, electrical signals, and chemical cues, all of which play a role in social interactions, territorial displays, and hunting behaviors.

Body Language

Sharks use physical movements to convey information, particularly in social and territorial contexts. Postural displays, such as arching the back, lowering pectoral fins, or exaggerated swimming patterns, serve as warnings to rivals or potential threats. The great white shark (Carcharodon carcharias) performs a distinct hunching motion, often accompanied by rapid tail movements, when asserting dominance or preparing to strike. Similarly, grey reef sharks (Carcharhinus amblyrhynchos) exhibit a threat display characterized by exaggerated side-to-side swimming and pectoral fin depression when confronted by divers or other sharks.

These visual signals help reduce unnecessary conflict by establishing dominance hierarchies or deterring intruders without resorting to aggression. Some sharks also use body positioning to coordinate group hunting strategies. Hammerhead sharks (Sphyrnidae) have been documented swimming in synchronized formations, possibly to herd prey or communicate intent within a school.

Electrical Signals

Sharks possess specialized sensory organs known as the ampullae of Lorenzini, which detect weak electrical fields generated by living organisms. While primarily used for hunting, this electroreception capability may also play a role in social behaviors such as schooling or mating.

Certain species, like the scalloped hammerhead (Sphyrna lewini), form large aggregations, particularly during mating seasons. Some researchers suggest electroreception helps these sharks maintain spatial awareness within a group, allowing them to detect nearby individuals even in low-visibility conditions.

Chemical Cues

Sharks rely on chemical signals to detect prey, identify potential mates, and navigate their environment. Their highly developed olfactory system enables them to detect minute concentrations of substances in the water, including pheromones released by other sharks. These chemical cues may influence reproductive behaviors, guiding individuals toward breeding grounds or signaling readiness to mate.

Studies on lemon sharks (Negaprion brevirostris) suggest chemical communication could influence social structuring, as juveniles tend to form stable groups, possibly mediated by scent recognition. Additionally, some species exhibit aggregation behaviors that may be driven by chemical attractants, such as those released by injured prey or conspecifics.

Acoustic Sensitivity And Reaction To Underwater Noise

Despite their lack of vocalization, sharks possess a well-developed auditory system that allows them to detect and respond to underwater sounds. Their inner ears contain structures called otoliths, which help them perceive low-frequency vibrations, particularly those between 10 and 800 Hz. This range overlaps with the frequencies produced by struggling prey, suggesting sharks may use passive listening to locate food sources. Some species, such as the lemon shark, have shown heightened sensitivity to pulsed or irregular noises that resemble the movements of injured fish.

Human-generated noise pollution is an increasing concern for marine life, and sharks are no exception. Vessel traffic, industrial activity, and underwater construction generate sound waves that propagate over long distances, creating a persistent auditory presence. Research indicates that excessive noise may interfere with a shark’s ability to detect prey or navigate using natural cues. Some species exhibit avoidance behaviors when exposed to high-intensity artificial sounds, suggesting certain frequencies may be distressing or disruptive. Changes in movement patterns, increased stress responses, and alterations in hunting efficiency have all been observed in response to elevated ambient noise levels.

Myths And Public Perception

The idea that sharks are completely silent has been reinforced by decades of media portrayals, documentaries, and fictional works emphasizing their stealth and predatory prowess. Unlike marine mammals known for complex vocalizations, sharks have long been depicted as relying solely on physical adaptations. The absence of widespread scientific evidence confirming deliberate vocalization has further cemented this belief.

Beyond sound production, public perception of shark communication remains limited. Many people associate sharks primarily with hunting behaviors, overlooking their sophisticated ways of interacting with their environment and one another. While they do not rely on vocal signals, their use of body language, electrical detection, and chemical cues allows for communication that is often underestimated. Misconceptions about their sensory abilities contribute to the broader misunderstanding of sharks as solitary, instinct-driven predators rather than adaptable marine organisms. Efforts to correct these misconceptions can foster a more nuanced appreciation of their ecological roles and behavioral intricacies.