Aquatic Mammals 2003, 29.2, 177–180 Pinniped vocal communication: an introduction Ronald J. Schusterman 1 and Soe M. Van Parijs 2 1 Long Marine Laboratory, University of California Santa Cruz, Santa Cruz, California, 95060, USA 2 Institute for Aquatic Biology, Norwegian College of Fisheries Science, University of Tromsø, Tromsø, Norway Communication forms the fabric of animal social life . . . in fact, looking at the way in which animals spend their time, it is striking how much of it they spend either inuencing, or being inuenced by, the behavior of other animals—in other words, in some form of communication. —Dawkins, Unraveling Animal Behavior, p. 71 The pinnipeds evolved and diverged tens of millions of years ago and spread throughout the oceans of the world, colonizing isolated shores and feeding in nearby productive waters. While the thirty-three living species of seals, sea lions, and walruses inhabit unique behavioural and ecological niches, one signicant commonality amongst these animals is the apparent structural complexity of their vocal- izations and the degree to which they use these vocalizations in communicative contexts. Some species, including the sea lions and some land- breeding seals, congregate seasonally on crowded rookeries where the repetitive calls of thousands of individuals swell into an incessant din. Other species, including most of the aquatically breeding seals, appear more reserved on their haul-outs, rarely producing audible sounds except for the occasional guttural threats of adults and the bleats of dependent pups. Many of these aquatic breeders were once thought to be relatively silent, but accumulating observations have shown them to have unusual and complex underwater vocal reper- toires. Among the pinnipeds, the walruses are the most amphibious callers of all, producing fre- quent and assorted aerial and underwater sounds. Intriguingly, all pinnipeds appear capable of sound production on land and in water, and some even emit calls simultaneously above and below the water’s surface. In addition to the quantity of vocalizations emit- ted by pinnipeds is the surprising diversity of the sounds themselves, which have been categorized by listeners as clicks, creaks, bleats, growls, barks, whinnies, buzzes, grunts, snorts, songs, pulses, trills, thumps, blasts, groans, sirens, sweeps, yelps, roars, hums, chirps, belches, squeals, bells, whistles, knocks, mews, chucks, glugs, coos, gongs, clacks, claps, drones, trumpets, whimpers, puVs, burps, snarls, hisses, warbles, moans, and bellows, among other descriptors. The variability in pinniped vocal signalling can be assessed at the level of the individ- ual, as well as by age and gender class, emotive state, geographic location, and species, and the diVerences documented thus far reect a degree of adaptation in vocal signalling that is rare among mammals. The acoustic characteristics of the sig- nals produced by pinnepeds are well-designed to gain the attention of conspecics—incidentally, these sounds have also captured the interest and imagination of human listeners. For centuries, seals have been signicant in the cultures of people living in close proximity to them. Not surprisingly, many of the legends and stories featuring these animals are concerned with their vocal communication. In these stories, seals may take on human form, talk and sing with people and with one another, and give warning of impending disaster (Maxwell, 1967; Thomson, 1914/1965). Many of these observations have been published as factual accounts. For example, Maxwell (1967) refers to a 1920’s newspaper article which states that ‘. . . there is undoubted testimony that the great grey seals of the Atlantic who visit the islands have been heard singing—for no other word applies to their very human voices.’ Many years later, a ‘talk- ing’ harbour seal named Hoover at the New England Aquarium rekindled the notion that seals could learn to speak (Ralls, et al., 1985). In the 1960’s, scientic exploration of pinniped vocal communication began in earnest, led by a handful of dedicated American investigators, including Thomas Poulter, Bill Scheville, Carlton Ray, Burney Le Bouef, Dick Peterson, Nicholas Collias, George Bartholomew, Ian Stirling, and one of the editors of this issue [RJS]. This early research tended to emphasize structural descriptions of aerial and underwater sounds emitted by readily accessible sea lions, fur seals, and elephant seals. In ? 2003 EAAM