Pinniped Sounds

Pinnipeds are a highly vocal clade of semiaquatic marine mammals, producing sounds above and below water. They originate from 13 of the 18 International Union for Conservation of Nature (IUCN) global regions (exceptions being the Caribbean, Central Indian, Arabian, East African, and East Asian regions). Of 34 IUCN-listed extant species (plus subspecies), 32 species have reports of sound production in air and 22 under water. Like other marine fauna, their call characteristics and cue rates (i.e., the number of calls produced per unit of time) are often related to biological traits, learned and innate acoustic behavior, the associated life functions, and the physical environment in which sounds are produced, which can vary among species and families. For example, feeding occurs in the water, while rearing pups mostly occurs in air (i.e., on land or ice) for all species. In contrast, courtship, a highly vocal activity, is conducted primarily on land by Otariidae (eared seals) but mostly at sea by Phocidae (earless seals) and Odobenidae (walruses). The physical limitations of producing sound under water and the differences between propagation in water and air mean that call characteristics and ecology for sound production in these two media should be considered separately. Inter- and intraspecies variation is significant and not necessarily related to phylogeny. Some closely related species display vastly different repertoires, while distantly related species can be similar in complexity and repertoire size, highlighting that most acoustic cues are derived traits. Descriptions of these sounds range from tonal calls, broadband grunts, roars, and barks to complex amplitude-modulated trills and chirps, repeated sequences, and song. Numerous species have displayed evidence of discrimination of physical traits based on acoustic characteristics, dialects, niche partitioning, vocal plasticity, anti-masking techniques, and call pattern sequencing and recognition—whether by pups, juveniles, or adults. Here, we collate data published in English to provide an overview of the pinniped families’ call characteristics, repertoires, and associated functions.