Underwater vocalizations and associated behavior in captive ringed seals (Pusa hispida)

The underwater vocal complexity of seals (Phocidae) is not related to their phylogeny

Closely related mammalian species often make similar vocalizations, but this is not so with the underwater calls of the true seals. Some seal species have diverse underwater vocal repertoires, whereas others only make pulsed calls. Vocal complexity scores of underwater calls of 13 seal species were compared with their phylogeny and life-history traits. Waveform types, repertoire sizes, repetition and rhythm patterns, and frequency and duration measures (15 attributes, scaled 0 to 1) were summed to give a vocal complexity score. The lowest complexity group use low frequency, burst pulse or irregular waveforms and have small repertoires. The intermediate group have both sinusoidal and noisy waveforms, songs, and a single rhythm pattern in repeated element calls. The most complex group have large repertoires, sinusoidal and noisy waveforms, songs, and two or more rhythm patterns in repeated element calls. There is no evidence of a relationship between phylogeny and vocal complexity. The low vocal complexity species are serially monogamous, do not form breeding groups, breed on beaches or pack ice, and are subject to higher predation risk. Species with higher vocal complexity are promiscuous or polygamous, form breeding groups on pack or landfast ice, and have a lower predation risk.

Assessing vessel slowdown for reducing auditory masking for marine mammals and fish of the western Canadian Arctic

Vessel slowdown may be an alternative mitigation option in regions where re-routing shipping corridors to avoid important marine mammal habitat is not possible. We investigated the potential relief in masking in marine mammals and fish from a 10 knot speed reduction of container and cruise ships. The mitigation effect from slower vessels was not equal between ambient sound conditions, species or vessel-type. Under quiet ambient conditions, a speed reduction from 25 to 15 knots resulted in smaller listening space reductions by 16-23%, 10-18%, 1-2%, 5-8% and 8% respectively for belugas, bowheads, bearded seals, ringed seals, and fish, depending on vessel-type. However, under noisy conditions, those savings were between 9 and 19% more, depending on the species. This was due to the differences in species' hearing sensitivities and the low ambient sound levels measured in the study region. Vessel slowdown could be an effective mitigation strategy for reducing masking.