Stingrays are flat-bodied fish belonging to the class Chondrichthyes, alongside sharks and skates. Adapted for life on the seafloor, their unique morphology influences how they interact with their environment. Unlike many bony fish that rely on auditory signals, the communication strategy of stingrays has long been considered a puzzle. However, their primary communication relies on a sophisticated array of non-acoustic signals and specialized sensory organs designed for their benthic existence.
Do Stingrays Produce Sound?
For a long time, rays and sharks were considered silent creatures because they lack the specialized organs, such as swim bladders or specialized bones, used by many bony fish to generate sound. This anatomical difference led to the assumption that their communication relied solely on other sensory channels.
Recent video evidence has challenged this belief, revealing that at least two species, the mangrove whipray and the cowtail stingray, can produce short, sharp clicking noises. These loud sounds are recorded when the rays are approached by divers, suggesting they function as a warning or distress signal. The exact mechanism remains unclear, but scientists hypothesize it involves a non-vocal process, possibly the rapid movement of the jaw, head, or the contraction of the spiracles. Spiracles are the openings behind the eyes used to draw water over the gills while resting on the seabed.
The clicks are within the hearing range of other stingrays, indicating a role in intraspecific communication, such as alerting others to danger. However, this acoustic behavior is primarily observed in response to a perceived threat, contrasting with the complex vocalizations seen in many bony fish. While the discovery of voluntary sound production is an evolving area of study, the majority of stingray communication relies on non-acoustic signals.
Non-Acoustic Signaling Between Stingrays
Stingrays primarily rely on non-acoustic signals to convey information about social status, aggression, and reproductive readiness. These methods include visual displays, chemical releases, and direct physical contact, which are effective in their often turbid, close-quarters habitat.
Visual communication is employed during social interactions, using body posture and specific movements to relay information. In competitive scenarios, a stingray may establish dominance through behavioral displays, creating a linear social hierarchy within a group. These visual cues are important in courtship, where the male signals his intentions to the female.
Tactile communication is a prominent feature of stingray reproduction, where direct physical contact transmits messages. During mating season, male stingrays physically grasp the female’s disc with their jaws, often leaving visible bite marks. These bites serve as communication, indicating the male’s interest and the female’s reproductive status. Physical contact may also play a role in social bonding, as suggested by cownose rays that actively seek physical touch in controlled environments.
Chemical signals, or pheromones, are used to communicate information over distance, particularly for reproductive purposes. Stingrays are macrosmatic, meaning they possess a highly developed sense of smell that is crucial for tracking and navigation. Pheromones released into the water signal a female’s readiness to mate, allowing a male to track her presence even when visual detection is impossible. These chemical traces provide detailed information about identity and reproductive state.
Specialized Sensory Perception
To effectively receive the non-acoustic signals they rely on, stingrays possess a specialized suite of sensory organs that function as a complex detection system.
Ampullae of Lorenzini
The Ampullae of Lorenzini is a network of jelly-filled canals and pores concentrated around the head and snout. These organs are electroreceptors, allowing the ray to detect incredibly weak electrical fields in the water. This electrosense is used to locate prey buried in the sand, as the ampullae detect the faint bioelectric fields generated by the muscle contractions of living organisms. Although primarily used for hunting, the Ampullae of Lorenzini may also have a role in detecting the weak electric fields generated by other rays. The network also helps the ray navigate by sensing the Earth’s magnetic field.
Lateral Line System
Mechanoreception is handled by the lateral line system, a series of fluid-filled canals and superficial sensors along the body, including the wings and tail. This system is sensitive to water movement, vibration, and pressure changes, essentially acting as a hydrodynamic antenna. The lateral line allows a ray to detect minute water displacements created by swimming organisms, which is useful for hunting and monitoring the approach of conspecifics or predators.
Chemoreception
Stingrays also possess a powerful chemoreceptive sense, often described as their primary means of long-distance detection. Water is drawn into the paired olfactory pits located on the underside of the snout, where specialized receptors detect dissolved chemical compounds. This sense of smell is highly sensitive to amino acids and other chemical cues, which enables the ray to track the chemical signatures of prey, predators, and potential mates.