Experimental field studies to measure behavioral responses of cetaceans to sonar

Abstract

Substantial recent progress has been made in directly measuring behavioral responses of free-ranging marine mammals to sound using controlled exposure experiments. Many studies were motivated by concerns about observed and potential negative effects of military sonar, including stranding events. Well-established experimental methods and increasingly sophisticated technologies have enabled fine-resolution measurement of many aspects of baseline behavior and responses to sonar. Studies have considered increasingly diverse taxa, but primarily odontocete and mysticete cetaceans that are endangered, particularly sensitive, or frequently exposed to sonar. This review focuses on recent field experiments studying cetacean responses to simulated or actual active military sonars in the 1 to 8 kHz band. Overall results demonstrate that some individuals of different species display clear yet varied responses, some of which have negative implications, while others appear to tolerate relatively high levels, although such exposures may have other consequences not measured. Responses were highly variable and may not be fully predictable with simple acoustic exposure metrics (e.g. received sound level). Rather, differences among species and individuals along with contextual aspects of exposure (e.g. behavioral state) appear to affect response probability. These controlled experiments provide critically needed documentation of identified behavioral responses occurring upon known sonar exposures, and they directly inform regulatory assessments of potential effects. They also inform more targeted opportunistic monitoring of potential responses of animals during sonar operations and have stimulated adaptations of field methods to consider increasingly realistic exposure scenarios and how contextual factors such as behavioral state and source proximity influence response type and probability.

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

“…In captivity, it has been possible to expose multiple individuals to a range of different sound levels, with each individual being allocated a specific dose in each experimental trial (Houser, Martin, & Finneran, , ). Several free‐ranging studies have conducted dose‐escalation experiments, in which the dose of sound increases over the duration of exposure (Southall et al., ). Captive and free‐ranging CEEs have resulted in dose–response functions for California sea lions Zalophus californianus (Houser et al., ), bottlenose dolphins Tursiops truncatus (Houser et al., ), harbour porpoise Phocoena phocoena (Kastelein, Gransier, van den Hoogen, & Hoek, ), killer whales (Harris et al., ; Miller et al., ), long‐finned pilot whales Globicephela melas (Antunes et al., ; Harris et al., ), sperm whales Physeter macrocephalus (Harris et al., ) and humpback whales Megaptera novaeangliae (Sivle et al., ; Wensveen, ), all in relation to naval sonar.…”

TurtleCam: A “Smart” Autonomous Underwater Vehicle for Investigating Behaviors and Habitats of Sea Turtles

“…To quantify behavioral response to sound, future deployments should include an acoustic tag (e.g., Tyson et al, 2017) and incorporate behavioral response studies. More research is needed on the behavioral response of sea turtles to anthropogenic underwater sounds, especially field studies that measure behavioral response experimentally as has been done for marine mammals (Southall et al, 2016).…”

Nowhere to go: noise impact assessments for marine mammal populations with high site fidelity

“…Beaked whales (predominately but not exclusively Cuvier's beaked whales) have been involved in atypical mass stranding events associated with MFAS training operations in many locations in the Northern Hemisphere (Brownell et al 2004, Cox et al 2006, Filadelfo et al 2009, Podestà et al 2016. Given these observations and fairly extensive recent research involving 4 beaked whale species, including Cuvier's beaked whales, those species tested appear to be particularly sensitive and vulnerable to certain types of acoustic disturbance relative to most other marine mammal species (see Southall et al 2016). Due to concerns over the vulnerability of beaked whales to acoustic disturbance, several research programs have been developed, providing new insights into the diving behavior and movements of these cryptic species.…”

“…More commonly, behavioral disturbance affects important activities such as feeding or reproductive behavior across a range of species and environments (e.g. Southall et al 2007Southall et al , 2016 (this Theme Section), Nowacek et al 2007, Blair et al 2016.…”