information:extraction
Communication

Pinnipeds can produce a number of vocalizations. While most vocals are audible to the human ear, Weddell seals have been recorded in Antarctica making ultrasonic calls underwater. In addition, the vocals of northern elephant seals may produce infrasonic vibrations. Vocals are produced both in air and underwater; the former are more common among otariids and the latter among phocids. Antarctic seals are noisier on land or ice than Arctic seals due to the absence of polar bears. Male vocals are usually deeper than those of the females. Vocalizations are particularly important during the breeding seasons. Dominant male elephant seals display their status and power with "clap-threats" and loud drum-like calls that may be modified by the proboscis. Male otariids have strong barks, growls and roars. Male walruses are known to produce gong -like calls when attempting to attract females, these are amplified underwater with inflatable throat sacs.

The Weddell seal has perhaps the most extensive vocal repertoire, producing both airborne and underwater sounds. Trilling, gluping, chirping, chugging and knocking are some examples of the calls produced underwater. When warning other seals, the calls may be pronounced by "prefixes" and "suffixes". The underwater vocals of Weddell seals can last 70 seconds, which is long for a marine mammal call. Some calls have about seven rhythm patterns and could be categorized as "songs". Similar calls have been recorded in other Antarctic seals and in bearded seals. In some pinniped species, there appear to be regional dialects or even individual variations in vocalizations. These differences are likely important for territorial males becoming accustomed to their neighbors (dear enemy effect) and mothers and pups who need to remain in contact on crowded beaches. Female seals emit a "pulsed, bawling" contact call, while pups respond by squawking. Contact calls are particularly important for otariid mothers returning from sea. Other vocalizations produced by seals include grunts, rasps, rattles, creaks, warbles, clicks and whistles.

Non-vocal communication is not as common in pinnipeds as in cetaceans. Nevertheless, when they feel threatened, hauled-out harbor seals and Baikal seals may slap themselves with their flippers to create a warning sound. Teeth chattering, hisses and exhalations are also made as aggressive warnings by pinnipeds. Visual displays also occur: Ross seals resting on the ice will show the stripes on their chests and bare their teeth to a perceived threat, while swimming Weddell seals will make an S-shaped posture to intimidate rivals under the ice. Male hooded seals use their inflatable nasal membranes to display to and attract females.