Classification of underwater vocalizations of wild spotted seals (Phoca largha) in Liaodong Bay, China.

Abstract

Underwater vocalizations were recorded and classified from wild spotted seals (Phoca largha) in Liaodong Bay, China. The spotted seals exhibited an extensive underwater vocal repertoire but with limited complexity. Four major call types, representing 77.8% of all calls recorded, were identified using multivariate analyses of ten acoustic parameters; knock, growl, drum, and sweep. The calls were relatively brief (12-270 ms, mean of -10 dB duration) pulsating sounds of low-frequency (peak frequency <600 Hz) and narrow bandwidth (169-232 Hz, mean of -3 dB bandwidth; 237-435 Hz, mean of -6 dB bandwidth). Frequency variables (-3/-6 dB frequency bandwidth, center frequency, and top three peak frequencies) were the primary descriptors used to differentiate the call types. Comparing the spotted seal underwater vocalizations with those of the closely related Pacific harbor seal (Phoca vitulina richardii) indicated that the two species use similar bandwidths and peak frequencies but spotted seal calls were generally shorter. Knowledge of underwater vocalizations of wild spotted seals is important for understanding the species behavior and for planning future acoustic surveys of its distribution and occurrence.