The popular image of a shark, often fueled by media, is that of a silent hunter gliding through the dark ocean depths. This widespread belief suggests that sharks are mute predators, relying solely on their other senses to navigate and find prey. However, the question of whether sharks communicate acoustically is complex. While they do not “speak” like marine mammals, their interaction with the underwater soundscape reveals a fascinating aspect of their biology.
The Direct Answer: Do Sharks Vocalize
The scientific consensus is that sharks do not vocalize in the traditional sense, primarily because they lack the necessary anatomical structures. Unlike bony fish, which use a specialized organ called a swim bladder and sonic muscles to produce sound, sharks have a cartilaginous skeleton and no swim bladder. This fundamental difference means they cannot generate controlled, intentional acoustic signals.
Sharks also lack vocal cords, the tissue folds found in the larynx of terrestrial animals and some marine mammals. Their auditory system is well-developed for hearing, allowing them to detect low-frequency vibrations over long distances. This sensitivity is particularly useful for locating struggling or wounded prey, which emit distinct low-frequency sounds typically below 1,000 Hertz.
Recent research suggests sharks are not completely silent, though their sounds are not true vocalizations. They cannot produce the complex, sustained, and modulated sounds characteristic of mammalian or bony fish communication. Instead, any sounds they create are typically byproducts of physical actions or distress.
Mechanically Produced Sounds
Although sharks cannot vocalize, they produce a variety of noises as a result of their behaviors and physical interactions. These mechanically produced sounds are incidental to their actions but can still serve as acoustic signals to other marine life. One example is the sharp, sudden sound of a shark snapping its jaws, often seen as a threat display in aggressive encounters or competition for food.
Splashing and breaching at the water’s surface also create significant acoustic disturbances, noticeable during feeding frenzies or mating pursuits. The rapid movement of a tail or the forceful impact of a body on the water generates low-frequency noise that travels well underwater. These sounds are not intentional “calls” but rather acoustic consequences of a shark’s activities.
A recent study documented the rig shark (Mustelus lenticulatus) producing distinct clicking sounds when handled by researchers. It is hypothesized that these rapid, broadband clicks, which occur mostly under stress, are created by the forceful clashing or snapping of their flattened teeth. This suggests a capacity for active sound production in response to disturbance, though the purpose may be a defensive startle response rather than social communication.
Alternative Communication Methods
Since acoustic signals are not their primary mode of communication, sharks rely on a sophisticated suite of sensory systems to interact with their environment and each other.
Visual Communication
Visual communication is prominent, especially in clear water, where sharks use body language to convey intent. The “agonistic display,” observed in species like the grey reef shark, is a highly exaggerated swimming pattern characterized by an arched back, dropped pectoral fins, and a lowered snout. This display is a clear visual warning, signaling that the shark is threatened and may attack if the intrusion continues. The shark essentially makes itself look larger and more threatening to avoid physical conflict. Other visual cues include specific swimming patterns that communicate social dominance or are part of courtship rituals.
Chemical Sensing
Sharks possess an extraordinary sense of smell and taste, allowing them to detect chemical signals, or pheromones, over vast distances. These chemical cues are instrumental in locating mates during breeding seasons and establishing feeding territories.
Electroreception
Their most unique sensory tool is electroreception, facilitated by the Ampullae of Lorenzini, a network of pores on the head filled with a conductive jelly. These specialized organs are incredibly sensitive, detecting the minute electrical fields generated by the muscle contractions and heartbeats of living organisms. While primarily used for close-range prey detection, this sense can also detect the faint bioelectrical fields of other sharks, potentially playing a role in social interaction or navigation by sensing the Earth’s magnetic field.