| Harp (Pagophilus groenlandicus) and Weddell ( Leptonychote weddellii) seal calling depth was investigated using a small vertical hydrophone array. Both rough depth approximations (< 35 m, ∼ 35 m or > 35 m) and more precise calling depth estimates (e.g., +/- 10 m) were obtained. Both species were found to vocalize throughout the water column, although they called predominately from shallower depths (generally ≤35 m). The seals also avoided sea-ice interference to some extent by diving well below the ice surface (to depths > 10 m) to emit the majority of their vocalizations. The vocalizations did not change over depth with respect to call types, subtypes, number of elements, rhythm patterns or total call duration, (or with respect to season and photoperiod for the Weddell seals). Frequency (kHz) of the calls did not increase with depth, indicating that the seals vocalize likely using the vocal cords of the larynx. |
