In natural and experimental conditions agonistic behaviour including sound communication was studied in four species of three Pinnipedia families: Odobenidae - Odobenus rosmarus divergens; Phocidae - Pusa caspica; and Otariidae - Callorhinus ursinus and Eumetopias jubatus. Among Pinnipedia which have periods when they form large agglomerations on the land during breeding and moulting, we found well developed agonistic interactions, involving a complex of threatening sounds. Three Pinnipedia families have three different types of agonistic interactions and sounds. Here we include long threatening trills in Phocidae, wide-range frequency coughing sounds in Otariidae, and brief low-frequency threatening sounds in Odobenidae. Different systems of agonistic displays in three Pinnipedia families confirm the different origin of these families. A common feature of all Pinnipedia is low-frequency wide-range frequency noisy sounds of threat, including sounds of noisy, vibrating breathing. Threat signals are part of the sound repertoire of Pinnipedia and represent an essential element of the mechanisms maintaining the pattern of a rookery population.
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