@article {58197, title = {Acoustically advertising male harbour seals in southeast Alaska do not make biologically relevant acoustic adjustments in the presence of vessel noise}, year = {2020}, abstract = {

Aquatically breeding harbour seal (Phoca vitulina) males use underwater vocalizations during the breeding season to establish underwater territories, defend territories against intruder males, and possibly to attract females. Vessel noise overlaps in frequency with these vocalizations and could negatively impact breeding success by limiting communication space. In this study, we investigated whether harbour seals employed anti-masking strategies to maintain communication in the presence of vessel noise in Glacier Bay National Park and Preserve, Alaska. Harbour seals in this location did not sufficiently adjust source levels or acoustic parameters of vocalizations to compensate for acoustic masking. Instead, for every 1 dB increase in ambient noise, signal excess decreased by 0.84 dB, indicating a reduction in communication space when vessels passed. We suggest that harbour seals may already be acoustically advertising at or near a biologically maximal sound level and therefore lack the ability to increase call amplitude to adjust to changes in their acoustic environment. This may have significant implications for this aquatically breeding pinniped, particularly for populations in high noise regions.

}, keywords = {acoustic communication, harbour seals, marine mammals, Noise, vocalizations}, doi = {10.1098/rsbl.2019.0795}, url = {https://royalsocietypublishing.org/doi/10.1098/rsbl.2019.0795}, author = {Matthews, Leanna P. and Fournet, Michelle E. H. and Gabriele, Christine and Klinck, Holger and Parks, Susan E.} } @article {57600, title = {Long-term evidence of noise-induced permanent threshold shift in a harbor seal ( Phoca vitulina )}, year = {2019}, abstract = {

In psychophysical studies of noise-induced hearing loss with marine mammals, exposure conditions are often titrated from levels of no effect to those that induce significant but recoverable loss of auditory sensitivity [temporary threshold shift (TTS)]. To examine TTS from mid-frequency noise, a harbor seal was exposed to a 4.1-kHz underwater tone that was incrementally increased in sound pressure level (SPL) and duration. The seal\&$\#$39;s hearing was evaluated at the exposure frequency and one-half octave higher (5.8\ kHz) to identify the noise parameters associated with TTS onset. No reliable TTS was measured with increasing sound exposure level until the second exposure to a 60-s fatiguing tone of 181\ dB re 1 \μPa SPL (sound exposure level 199\ dB re 1 \μPa2s), after which an unexpectedly large threshold shift (\>47\ dB) was observed. While hearing at 4.1\ kHz recovered within 48\ h, there was a permanent threshold shift of at least 8\ dB at 5.8\ kHz. This hearing loss was evident for more than ten years. Furthermore, a residual threshold shift of 11\ dB was detected one octave above the tonal exposure, at 8.2\ kHz. This hearing loss persisted for more than two years prior to full recovery.

}, doi = {10.1121/1.5129379}, url = {http://asa.scitation.org/doi/10.1121/1.5129379}, author = {Reichmuth, Colleen and Jillian M. Sills and Mulsow, Jason and Ghoul, Asila} }