Marine mammals and sonar: Dose‐response studies, the risk‐disturbance hypothesis and the role of exposure context

Abstract

Marine mammals may be negatively affected by anthropogenic noise. Behavioural response studies (BRS) aim to establish a relationship between noise exposure conditions (dose) from a potential stressor and associated behavioural responses of animals. A recent series of BRS have focused on the effects of naval sonar sounds on cetaceans. Here, we review the current state of understanding of naval sonar impact on marine mammals and highlight knowledge gaps and future research priorities. Many marine mammal species exhibit responses to naval sonar sounds. However, responses vary between and within individuals and populations, highlighting the importance of exposure context in modulating dose–response relationships. There is increasing support from both terrestrial and marine systems for the risk‐disturbance hypothesis as an explanation for underlying response processes. This proposes that sonar sounds may be perceived by animals as a threat, evoking a response shaped by the underlying species‐specific risk of predation and anti‐predator strategy. An understanding of responses within both the dose–response and risk‐disturbance frameworks may enhance our ability to predict responsiveness for unstudied species and populations. Many observed behavioural responses are energetically costly, but the way that these responses may lead to long‐term individual and population‐level impacts is poorly understood. Synthesis and applications. Behavioural response studies have greatly improved our understanding of the potential effects of naval sonar on marine mammals. Despite data gaps, we believe a dose‐response approach within a risk‐disturbance framework will enhance our ability to predict responsiveness for unstudied species and populations. We advocate for (1) regulatory frameworks to utilize peer‐reviewed research findings when making predictions of impact, (2) regulatory frameworks to account for the inherent uncertainty in predictions of impact and (3) investment in monitoring programmes that are both directed by recent research and offer opportunities for validation of predictions at the individual and population level.

Understanding the population consequences of disturbance

“…The initial step in implementing the PCoD framework (Figure ) is the quantification of the physiological and behavioral responses of individuals to a known or potential stressor. Controlled exposure experiments (Harris et al., ) have used electronic loggers to assess changes in the movement and vocalizations of marine mammals exposed to military sonar and air guns used for seismic surveys (Dunlop et al., ; Wensveen et al., ). Loggers have also been applied to monitor marine mammal responses to actual disturbance events; for example, of Cuvier's beaked whales ( Ziphius cavirostris ) to sonar exercises (Falcone et al., ) as well as of harbor seals ( Phoca vitulina ) to pile driving for wind farm construction (Russell et al., ) and to pedestrian and vessel approaches at their haul‐outs (Andersen, Teilmann, Dietz, Schmidt, & Miller, ).…”

Population‐level consequences of seismic surveys on fishes: An interdisciplinary challenge

“…Example of how exposure to an acoustic stressor (of particular Sound Pressure Level) can affect the tendency to modify baseline behaviour (Behavioural Response) in a typical dose–response curve (based on killer whale ( Orcinus orca , Delphinidae) data from a behavioural response study into acoustic exposure with naval sonar (Miller et al., ; also see Harris et al., )) [Colour figure can be viewed at wileyonlinelibrary.com]…”

Measuring responses of harbour seals to potential aversive acoustic mitigation signals using controlled exposure behavioural response studies

“…reviewed by Harris et al, 2018), but no dedicated fieldwork to derive the same information for wild phocids. reviewed by Harris et al, 2018), but no dedicated fieldwork to derive the same information for wild phocids.…”