01993nas a2200145 4500008004100000245011600041210006900157520145700226100002601683700002001709700002001729700002401749700002301773856005101796 2019 eng d00aHigh-amplitude vocalizations of male northern elephant seals and associated ambient noise on a breeding rookery0 aHighamplitude vocalizations of male northern elephant seals and 3 a

Northern elephant seals (Mirounga angustirostris) are massive, land-breeding marine mammals that produce loud, stereotyped calls during annual breeding seasons. To determine vocalization source levels emitted by competing males on a mainland breeding rookery, aerial calls were measured on-axis at 1 m from adult males using three different sound pressure level metrics. Time-averaged (1 min) ambient noise was also measured under variable environmental and social conditions. Results indicate that male northern elephant seals emit high amplitude airborne calls with little variation in call amplitude. Mean source levels ranged from 98 to 114 dB re: 20 μPa [root-mean-square (rms) -fast], 102–116 dB re: 20 μPa (rms-impulse), and 120–131 dB re: 20 μPa (peak) and average standard deviations for all metrics were <2.3 dB. Further, these seal rookeries exhibit high variability in ambient noise (in terms of both spectrum and amplitude) from biotic and environmental sources. Finally, males sampled did not adjust call amplitude to compensate for higher background noise levels and thus did not exhibit a Lombard effect. These findings reinforce the view that the remarkable vocalizations of male northern elephant seals serve as rigid and powerful signals that convey individual identity within noisy breeding colonies rather than as honest indicators of size, status, or motivation.

1 aSouthall, Brandon, L.1 aCasey, Caroline1 aHolt, Marla, M.1 aInsley, Stephen, J.1 aReichmuth, Colleen uhttp://asa.scitation.org/doi/10.1121/1.513942201790nas a2200133 4500008004100000245012300041210006900164520129100233100002301524700002301547700001801570700001701588856005101605 2019 eng d00aLong-term evidence of noise-induced permanent threshold shift in a harbor seal ( Phoca vitulina )0 aLongterm evidence of noiseinduced permanent threshold shift in a3 a

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'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.

1 aReichmuth, Colleen1 aSills, Jillian, M.1 aMulsow, Jason1 aGhoul, Asila uhttp://asa.scitation.org/doi/10.1121/1.512937901896nas a2200169 4500008004100000022001400041245012700055210006900182260001600251300001600267490000800283520131900291100002301610700001901633700002301652856005101675 2018 eng d a0001-496600aThe production and reception of underwater sound in Hawaiian monk seals ( Neomonachus schauinslandi )0 aproduction and reception of underwater sound in Hawaiian monk se cJan-09-2018 a1741 - 17410 v1443 a

The endangered Hawaiian monk seal is a primitive phocid (true) seal endemic to the tropical Hawaiian Islands. At present, there is a lack of substantive bioacoustic information available for this species, with no formal descriptions of underwater vocalizations and limited data concerning underwater hearing. To address these knowledge gaps, we are working to better understand species-typical auditory capabilities and sound production by thoroughly evaluating a single individual living in human care. A mature male monk seal was trained to perform an auditory go/no-go signal detection task in water. Detection thresholds were measured for narrowband tones across the frequency range of hearing to generate a full underwater audiogram. Additionally, an acoustic recorder was placed in this monk seal’s living enclosure for a full year, enabling characterization of his underwater repertoire and seasonal trends in vocal behavior. This study presents the first examination of underwater vocalizations in Hawaiian monk seals, provides insight into the perceptual abilities of this species and the evolution of underwater hearing within the phocid lineage, and enables improved assessments of noise effects on these vulnerable seals. [Work supported by Navy’s Living Marine Resources Program.]

1 aSills, Jillian, M.1 aParnell, Kirby1 aReichmuth, Colleen uhttp://asa.scitation.org/doi/10.1121/1.5067723