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As human activities impact virtually every animal habitat on the planet, identifying species at-risk from disturbance is a priority. Cetaceans are an example taxon where responsiveness to anthropogenic noise can be severe but highly species and context specific, with source–receiver characteristics such as hearing sensitivity only partially explaining this variability. Here, we predicted that ecoevolutionary factors that increase species responsiveness to predation risk also increase responsiveness to anthropogenic noise. We found that reductions in intense-foraging time during exposure to 1- to 4-kHz naval sonar and predatory killer whale sounds were highly correlated (r = 0.92) across four cetacean species. Northern bottlenose whales ceased foraging completely during killer whale and sonar exposures, followed by humpback, long-finned pilot, and sperm whales, which reduced intense foraging by 48 to 97%. Individual responses to sonar were partly predicted by species-level responses to killer whale playbacks, implying a similar level of perceived risk. The correlation cannot be solely explained by hearing sensitivity, indicating that species- and context-specific antipredator adaptations also shape cetacean responses to human-made noise. Species that are more responsive to predator presence are predicted to be more disturbance sensitive, implying a looming double whammy for Arctic cetaceans facing increased anthropogenic and predator activity with reduced ice cover.

The time and energetic costs of behavioral responses to incidental and experimental sonar exposures, as well as control stimuli, were quantified using hidden state analysis of time series of acoustic and movement data recorded by tags ( DTAG ) attached to 12 sperm whales ( Physeter macrocephalus ) using suction cups. Behavioral state transition modeling showed that tagged whales switched to a non‐foraging, non‐resting state during both experimental transmissions of low‐frequency active sonar from an approaching vessel ( LFAS ; 1–2 kH z, source level 214 dB re 1 μPa m, four tag records) and playbacks of potential predator (killer whale, Orcinus orca ) sounds broadcast at naturally occurring sound levels as a positive control from a drifting boat (five tag records). Time spent in foraging states and the probability of prey capture attempts were reduced during these two types of exposures with little change in overall locomotion activity, suggesting an effect on energy intake with no immediate compensation. Whales switched to the active non‐foraging state over received sound pressure levels of 131–165 dB re 1 μPa during LFAS exposure. In contrast, no changes in foraging behavior were detected in response to experimental negative controls (no‐sonar ship approach or noise control playback) or to experimental medium‐frequency active sonar exposures ( MFAS ; 6–7 kH z, source level 199 re 1 μPa m, received sound pressure level [ SPL ] = 73–158 dB re 1 μPa). Similarly, there was no reduction in foraging effort for three whales exposed to incidental, unidentified 4.7–5.1 kH z sonar signals received at lower levels ( SPL = 89–133 dB re 1 μPa). These results demonstrate that similar to predation risk, exposure to sonar can affect functional behaviors, and indicate that increased perception of risk with higher source level or lower frequency may modulate how sperm whales respond to anthropogenic sound.

Naval sonar can disrupt beaked whale diving behaviour, in some cases leading to lethal strandings. Diving disruption likely involves a physiological response, which remains poorly understood. Beaked whales may exceed their aerobic dive limit during long-duration deep-foraging dives and later in those dives, during ascent, initiate a unique strong gait (B-strokes), hypothesized to recruit anaerobic fast-twitch fibres. We compared the use of B-strokes during exposed and unexposed dives in four species of beaked whales. Contrasting the highly context-specific use of B-strokes during ascents from deep-dives in baseline conditions, during sonar exposure, B-strokes were used during descent and ascent phases of both deep and shallow dives. B-stroke onset occurred during all sonar exposure periods with levels above 100 dB re 1 µPa that lasted more than three minutes. The use of B-strokes during descent indicates these animals start using an oxygen-saving strategy earlier in exposed (16 ± 13 min) vs. unexposed dives (33 ± 14 min). This change in swimming gait when exposed to an external threat likely evolved to enable flexible escape responses from predators. However, if prolonged, such responses could lead to physiological changes that contribute to gas bubble formation and growth that could lead to animals stranding.

Modern long-range naval sonars are a potential disturbance for marine mammals and can cause disruption of feeding in cetaceans. We examined the lunge-feeding behaviour of humpback whales Megaptera novaeangliae before, during and after controlled exposure experiments with naval sonar by use of acoustic and motion sensor archival tags attached to each animal. Lunge-feeding by humpback whales entails a strong acceleration to increase speed before engulfing a large volume of prey-laden water, which can be identified by an acoustic signature characterized by a few seconds of high-level flow-noise followed by a rapid reduction, coinciding with a peak in animal acceleration. Over 2 successive seasons, 13 humpback whales were tagged. All were subject to a no-sonar control exposure, and 12 whales were exposed to 2 consecutive sonar exposure sessions, with 1 h between sessions. The first sonar session resulted in an average 68% reduction in lunge rate during exposure compared to pre-exposure, and this reduction was significantly greater than any changes observed during the no-sonar control. During the second sonar session, reduction in lunge rate was 66% during sonar exposure compared to the pre-exposure level, but was not significant compared to the no-sonar control, likely due to a larger inter-individual variability because some individuals appeared to have habituated whereas others had not. Our results indicate that naval sonars operating near humpback whale feeding grounds may lead to reduced foraging and negative impacts on energy balance.

The time and energetic costs of behavioral responses to incidental and experimental sonar exposures, as well as control stimuli, were quantified using hidden state analysis of time series of acoustic and movement data recorded by tags (DTAG) attached to 12 sperm whales (Physeter macrocephalus) using suction cups. Behavioral state transition modeling showed that tagged whales switched to a non-foraging, non-resting state during both experimental transmissions of low-frequency active sonar from an approaching vessel (LFAS; 1–2 kHz, source level 214 dB re 1 μPa m, four tag records) and playbacks of potential predator (killer whale, Orcinus orca) sounds broadcast at naturally occurring sound levels as a positive control from a drifting boat (five tag records). Time spent in foraging states and the probability of prey capture attempts were reduced during these two types of exposures with little change in overall locomotion activity, suggesting an effect on energy intake with no immediate compensation. Whales switched to the active non-foraging state over received sound pressure levels of 131–165 dB re 1 μPa during LFAS exposure. In contrast, no changes in foraging behavior were detected in response to experimental negative controls (no-sonar ship approach or noise control playback) or to experimental medium-frequency active sonar exposures (MFAS; 6–7 kHz, source level 199 re 1 μPa m, received sound pressure level [SPL] = 73–158 dB re 1 μPa). Similarly, there was no reduction in foraging effort for three whales exposed to incidental, unidentified 4.7–5.1 kHz sonar signals received at lower levels (SPL = 89–133 dB re 1 μPa). These results demonstrate that similar to predation risk, exposure to sonar can affect functional behaviors, and indicate that increased perception of risk with higher source level or lower frequency may modulate how sperm whales respond to anthropogenic sound.

Controlled exposure experiments using 1 to 2 kHz sonar signals were conducted with 11 humpback whales (Megaptera novaeangliae), one minke whale (Balaenoptera acutorostrata), and one northern bottlenose whale (Hyperoodon ampullatus) during three field trials from 2011 to 2013. Ship approaches without sonar transmissions, playbacks of killer whale vocalizations, and broadband noise were conducted as controls. Behavioural parameters such as horizontal movement, diving, social interactions, and vocalizations were recorded by animal-attached tags and by visual and acoustic tracking. Based on these data, two expert panels independently scored the severity of behavioural changes that were judged likely to be responses to the experimental stimuli, using a severity scale ranging from no effect (0) to high potential to affect vital rates (9) if exposed repeatedly. After scoring, consensus was reached with a third-party moderator. In humpback whales, killer whale playbacks induced more severe responses than sonar exposure, and both sonar exposures and killer whale playbacks induced more responses and responses of higher severity than the no-sonar ship approaches and broadband noise playbacks. The most common response during sonar exposures in all three species was avoidance of the sound source. The most severe responses to sonar (severity 8) were progressive high-speed avoidance by the minke whale and long-term area avoidance by the bottlenose whale. Other severe responses included prolonged avoidance and cessation of feeding (severity 7). The minke whale and bottlenose whale started avoiding the source at a received sound pressure level (SPL) of 146 and 130 dB re 1 μPa, respectively. Humpback whales generally had less severe responses that were triggered at higher received levels. The probability of severity scores with the potential to affect vital rates increased with increasing sound exposure level ([SEL.sub.cum]). The single experiments with minke and bottlenose whales suggest they have greater susceptibility to sonar disturbance than humpback whales, but additional studies are needed to confirm this result.

Many marine mammals rely on sound for foraging, maintaining group cohesion, navigation, finding mates, and avoiding predators. These behaviors are potentially disrupted by anthropogenic noise. Behavioral responses to sonar have been observed in a number of baleen whale species but relatively little is known about the responses of minke whales ( Balaenoptera acutorostrata ). Previous analyses demonstrated a spatial redistribution of localizations derived from passive acoustic detections in response to sonar activity, but the lack of a mechanism for associating localizations prevented discriminating between movement and cessation of calling as possible explanations for this redistribution. Here we extend previous analyses by including an association mechanism, allowing us to differentiate between movement responses and calling responses, and to provide direct evidence of horizontal avoidance responses by individual minke whales to sonar during U.S. Navy training activities. We fitted hidden Markov models to 627 tracks that were reconstructed from 3 years of minke whale ( B. acutorostrata ) vocalizations recorded before, during, and after naval training events at the U.S. Navy’s Pacific Missile Range Facility, Kauai, Hawaii. The fitted models were used to identify different movement behaviors and to investigate the effect of sonar activity on these behaviors. Movement was faster and more directed during sonar exposure than in baseline phases. The mean direction of movement differed during sonar exposure, and was consistent with movement away from sonar-producing ships. Animals were also more likely to cease calling during sonar. There was substantial individual variation in response. Our findings add large-sample support to previous demonstrations of horizontal avoidance responses by individual minke whales to sonar in controlled exposure experiments, and demonstrate the complex nature of behavioral responses to sonar activity: some, but not all, whales exhibited behavioral changes, which took the form of horizontal avoidance or ceasing to call.

Time allocation to different activities and habitats enables individuals to modulate their perceived risks and access to resources and can reveal important trade‐offs between fitness‐enhancing activities (e.g., feeding vs. social behavior). Species with long reproductive cycles and high parental investment, such as marine mammals, rely on such behavioral plasticity to cope with rapid environmental change, including anthropogenic stressors. We quantified activity budgets of free‐ranging long‐finned pilot whales in order to assess individual time trade‐offs between foraging and other behaviors in different individual and ecological contexts, and during experimental sound exposures. The experiments included 1–2 and 6–7 kHz naval sonar exposures (a potential anthropogenic stressor), playback of killer whale (a potential predator/competitor) vocalizations, and negative controls. We combined multiple time series data from digital acoustic recording tags (DTAG) as well as group‐level social behavior data from visual observations of tagged whales at the surface. The data were classified into near‐surface behaviors and dive types (using a hidden Markov model for dive transitions) and aggregated into time budgets. On average, individuals (N = 19) spent most of their time (69%) resting and transiting near surface, 21% in shallow dives (depth <40 m), and only 10% of their time in deep foraging dives, of which 65% reached a depth 10 m from the sea bottom. Individuals in the largest of three body size classes or accompanied by calves tended to spend more time foraging than others. Simultaneous tagging of pairs of individuals showed that up to 50% of the activity budget was synchronized between conspecifics with decreased synchrony during foraging periods. Individuals spent less time foraging when forming larger non‐vocal aggregations of individuals in late afternoons, and more time foraging when in the mid‐range of water depths (300–400 m) available in the study area (50–700 m). Individuals reduced foraging time by 83% (29–96%) during their first exposure to sonar, but not during killer whale sound playbacks. A relative increase in foraging during repeat sonar exposures indicated habituation or change in response tactic. We discuss the possible adaptive value of these trade‐offs in time allocation to reduce individual conflict while maintaining benefits of group living.

Controlled exposure experiments (CEEs) have demonstrated that naval pulsed active sonar (PAS) can induce costly behavioral responses in cetaceans similar to antipredator responses. New generation continuous active sonars (CAS) emit lower amplitude levels but more continuous signals. We conducted CEEs with PAS, CAS and no-sonar control on free-ranging sperm whales in Norway. Two panels blind to experimental conditions concurrently inspected acoustic-and-movement-tag data and visual observations of tagged whales and used an established severity scale (0–9) to assign scores to putative responses. Only half of the exposures elicited a response, indicating overall low responsiveness in sperm whales. Responding whales (10 of 12) showed more, and more severe responses to sonar compared to no-sonar. Moreover, the probability of response increased when whales were previously exposed to presence of predatory and/or competing killer or long-finned pilot whales. Various behavioral change types occurred over a broad range of severities (1–6) during CAS and PAS. When combining all behavioral types, the proportion of responses to CAS was significantly higher than no-sonar but not different from PAS. Responses potentially impacting vital rates i.e., with severity ≥4, were initiated at received cumulative sound exposure levels (dB re 1 μPa2 s) of 137–177 during CAS and 143–181 during PAS.

A seven-year time series of fin whale (Balaenoptera physalus) acoustic detections in the Equatorial Pacific Ocean was examined in combination with regional environmental parameters to better understand fin whale seasonal distribution and behavioral ecology in a traditionally undersampled ocean region. Ecological modeling of environmental variables related to fin whale vocal presence indicated that median sound pressure spectral density level in the 5 to 115 Hz band, chlorophyll concentration, and sea surface temperature (SST) were the strongest predictors of fin whale presence. Fin whale vocal presence increased with increasing median sound level and decreased with increasing SST. Variation in seasonal fin whale call density and estimated animal density varied annually with one of the largest estimates occurring in the only year of the study when both the El Nino--Southern Oscillation and Pacific Decadal Oscillation were in a positive phase. This work illustrates the feasibility and value of applying knowledge of call detection bearings and received levels from long-term, sparse array recordings to estimate animal density of marine mammals in the context of regional environmental conditions. Key Words: acoustics, density estimation, environmental modeling, fin whale, Balaenoptera physalus