Seals, captivating marine mammals inhabiting diverse aquatic environments, are widely recognized for their distinctive vocalizations. Among these sounds, barking is a prominent characteristic. This unique acoustic behavior is fundamental to their communication. Understanding this barking sound provides insight into the complex social lives of these amphibious creatures.
Defining Seal Barking
Seal barking is a loud, guttural, often dog-like sound. While “barking” is a commonly used term, seal vocalizations encompass a wide range of sounds, and not all seal species bark with the same intensity or frequency. California sea lions and fur seals are known for frequent barking, while other species have different vocal repertoires. These barks are just one part of their broader communication system, which can include growls, honks, moans, and even whistles.
Why Seals Bark
Seals bark for various reasons, primarily for communication within their colonies. One significant purpose is territorial defense, where seals, especially males, bark to establish and maintain their personal space or prime breeding and resting locations against other individuals. During the breeding season, male California sea lions bark incessantly to define their territories, and continue to bark to defend them once established. An intruding male can trigger an immediate and forceful barking response from the resident male, often accompanied by physical displays.
Barking also plays a significant role in mating rituals, particularly for males seeking to attract females and assert dominance over rivals. This vocalization helps to communicate their presence and readiness to mate, reinforcing their status within the breeding hierarchy.
In addition to these interactions, barking can serve as an alarm or warning signal, alerting other seals to potential threats such as predators like sharks or orcas, or disturbances caused by humans. This collective warning helps to enhance the safety of the entire colony.
General social communication within a colony also involves barking, helping to maintain cohesion among individuals or to express agitation. For instance, during non-breeding periods, submissive male California sea lions tend to be more vocal than dominant males.
The Biology of Seal Vocalization
The production of vocalizations, including barking, in seals relies on anatomical structures similar to those found in other mammals. Primarily, seals use their vocal cords located within the larynx to generate sounds. Air pressure from the lungs forces air through the glottis, causing the vocal cords to vibrate and produce sound. This initial sound is then filtered and modified by the length and geometry of the upper vocal tract, which includes the throat, mouth, and nasal passages.
While seals vocalize both on land and underwater, barking is predominantly an airborne sound. The anatomical structure of the larynx in various seal species, such as the harbor seal and gray seal, appears broadly similar to that of most other mammals. However, some species like elephant seals, sea lions, and walruses exhibit unusual features, such as extremely large and rounded arytenoid cartilages, which form a valve across approximately half of the laryngeal lumen. The vocal folds in elephant seals and sea lions are also rotated compared to terrestrial mammals, with the ventral attachment positioned more rostrally. These adaptations may indicate evolutionary convergence with other underwater vocalizers, although the primary function of barks remains in the air.