Observations on the mechanisms and phenomena underlying vocalizations of the gray seals

Abstract

Gray seals vocalize both underwater and above the water surface using variety of sounds. The analysis of the differences in acoustic parameters of the emitted sounds suggests that the underlying phenomena may involve several different, independent mechanisms, which have not been yet investigated and understood. The aim of the present study is to introduce some important conclusions regarding those mechanisms and phenomena, based on the results of the original, long-term experimental investigations, and observations carried out at the sealarium of the Hel Marine Station of the University of Gdansk. Several thousands of vocalizations emitted by the mature specimens and cubs were recorded above and beneath the water surface, and analyzed for their acoustic parameters using the dedicated, developed software. The observations also involved video recording combined with synchronous acquisition of underwater sounds, which allowed to link the acoustic phenomena with the specific behavior of the animals. Based on the obtained results, the equivalent mechanical models of the corresponding anatomical structures responsible for generation of various sounds are proposed. An own, original classification of the vocalizations of the gray seals, based on the assumed separation of the involved generation mechanisms, is introduced.