Impacts of Navy Sonar on Whales and Dolphins: Now beyond a Smoking Gun?

Abstract

The risks military sonar poses to cetaceans received international attention with a highly-publicized mass stranding of Cuvier's beaked whales (Ziphius cavirostris), Blainville's beaked whales (Mesoplodon densirostris), and northern minke whales (Balaenoptera acutorostrata) in the Bahamas in 2000. This was the first time that the US Government determined a stranding to be the result of mid-frequency active sonar use. Subsequently attention has been drawn to other mass strandings coincident with naval exercises, including events preceding the 2000 mass stranding. The list of species for which mass strandings have been linked to naval exercises has also increased to include other beaked whales, dwarf and pygmy sperm whales (Kogia spp.), pilot whales (Globicephala spp.), several dolphin species (Stenella sp. and Delphinus delphis), and harbor porpoises (Phocoena phocoena). In particular, there have been several mass strandings in the northern Indian Ocean coincident with naval exercises-including one of the largest (200-250 dolphins)-which have received little attention. Changes in beaked whale behavior, including evasive maneuvering, have been recorded at received levels below <100 dB re 1 µPa (rms) and mass stranding may occur at received levels potentially as low as 150-170 dB re 1 µPa. There is strong scientific evidence to suggest that a wide range of whale, dolphin and porpoise species can also be impacted by sound produced during military activities, with significant effects occurring at received levels lower than previously predicted. Although there are many stranding events that have occurred coincident with the presence of naval vessels or exercises, it is important to emphasize that even the absence of strandings in a region does not equate to an absence of deaths, i.e., absence of evidence does not mean evidence of absence. Strandings may be undetected, or be unlikely to be observed because of a lack of search effort or due to coastal topography or characteristics. There may also be "hidden" impacts of sonar and exercises not readily observable (e.g., stress responses). Due to the level of uncertainty related to this issue, ongoing baseline monitoring for cetaceans in exercise areas is important and managers should take a precautionary approach to mitigating impacts and protecting species.

Bio‐energetic modeling of medium‐sized cetaceans shows high sensitivity to disturbance in seasons of low resource supply

“…, Fleishman et al. , Parsons ). Several sources of disturbance (ship traffic, seismic surveys, military sonar) can lead to a variety of responses and impacts on marine mammals, such as decrease/cessation of feeding, avoidance behavior, temporary and permanent effects on hearing, and death (National Research Council ).…”

“…, Tyack et al. , Parsons ). While the link between disturbance and its (short term) effect on behavior, feeding, and health of individuals is becoming more apparent (Miller , Sivle et al.…”

“…The increase of human activity in the marine environment has led to concern about the effects of disturbance on marine mammals (Halpern et al 2008, DeRuiter et al 2013, Maxwell et al 2013, Fleishman et al 2016, Parsons 2017. Several sources of disturbance (ship traffic, seismic surveys, military sonar) can lead to a variety of responses and impacts on marine mammals, such as decrease/cessation of feeding, avoidance behavior, temporary and permanent effects on hearing, and death (National Research Council 2003).…”

Biodiversity conservation and armed conflict: a warfare ecology perspective

“…Sensitivity of wildlife to the noise and disturbance of military training varies widely by taxa and context. Desert tortoise ( Gopherus agassizii ) health and abundance decreased with proximity to training activities at Fort Irwin, California, and multiple strandings and behavioral disturbances to whales and dolphins have occurred in proximity to the use of active naval sonar arrays . In an extreme case, underwater shock waves from 137 nuclear tests at Mururoa Atoll between 1976 and 1995 caused repeated, and nearly complete defaunation of fish communities within a 12.5 km 2 area .…”

Abundance, activity and critical habitat of the striped dolphinStenella coeruleoalbain the Gulf of Taranto (northern Ionian Sea, central Mediterranean Sea)

“…Concerning the Ionian Sea (central‐eastern Mediterranean Sea), recent studies confirm that the striped dolphin regularly inhabits the Gulf of Taranto (northern Ionian Sea) (Carlucci et al, ; Dimatteo et al, ). Here, the species could be exposed to elevated levels of anthropogenic threats such as strikes from merchant traffic, disturbance from high intensity military sonar and exposure to chemical pollution from the nearby harbour of Taranto (Cardellicchio, Giandomenico, Ragone, & Di Leo, ; Dolman, Williams‐Grey, Asmutis‐Silvia, & Isaac, ; Gisiner, ; Marsili & Focardi, ; Notarbartolo di Sciara & Gordon, ; Parsons, ). These conditions represent a potential threat to the long‐term survival of the species, reducing its habitat suitability as a behavioural response to local human‐induced environmental changes (Carlucci et al, ).…”