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/10.1121/1.513942201972nas a2200157 4500008004100000245011400041210006900155520140900224100002001633700002001653700002401673700002001697700002301717700002301740856005101763 2019 eng d00aSounds associated with foraging and prey capture in individual fish-eating killer whales, Orcinus orca0 aSounds associated with foraging and prey capture in individual f3 a

Foraging behavior in odontocetes is fundamentally tied to the use of sound. Resident-type killer whales use echolocation to locate and capture elusive salmonid prey. In this investigation, acoustic recording tags were suction cup-attached to endangered Southern Resident killer whales to describe their acoustic behavior during different phases of foraging that, along with detections of prey handling sounds (e.g., crunches) and observed predation events, allow confirmation of prey capture. Echolocation click trains were categorized based on the inter-click interval (ICI) according to hypothesized foraging function. Whales produced slow click trains (ICI >100 ms) at shallowest depths but over the largest change of depth, fast click trains (10 ms < ICI ≤100 ms) at intermediate depths, and buzz trains (ICI ≤10 ms) at deepest depths over the smallest depth change. These results align with hypotheses regarding biosonar use to search, pursue and capture prey. Males exhibited a higher probability of producing slow click trains, buzzes and prey handling sounds, indicating higher levels of prey searching and capture to support the energy requirement of their larger body size. These findings identify relevant acoustic indicators of subsurface foraging behaviors of killer whales, enabling investigations of human impacts on sound use and foraging.

1 aHolt, Marla, M.1 aHanson, Bradley1 aEmmons, Candice, K.1 aHaas, David, K.1 aGiles, Deborah, A.1 aHogan, Jeffrey, T. uhttp://asa.scitation.org/doi/10.1121/1.5133388